Design, modeling and control of a micro-robotic tip for...

Numéro d'ordre : 2005-ISAL-00107 Année 2005

THESE

présentée

DEVANT L'INSTITUT NATIONAL DES SCIENCES APPLIQUEES DE LYON

pour obtenir

LE GRADE DE DOCTEUR

ECOLE DOCTORALE : ELECTRONIQUE, ELECTROTECHNIQUE ET AUTOMATIQUE SPECIALITE : AUTOMATIQUE INDUSTRIELLE

par

Gang CHEN

Design, modeling and control of a micro-robotic tip for colonoscopy

Soutenance prévue le 2 Décembre 2005 devant la commission d'examen

Jury : Yacine AMIRAT Professeur LISSI – Université Paris XII Rapporteur Maurice BETEMPS Professeur LAI – INSA de Lyon Examinateur Philippe BIDAUD Professeur LRP - Université Paris VI Examinateur Michel de MATHELIN Professeur LSIIT - ENSP Strasbourg Rapporteur Minh Tu PHAM MCF LAI – INSA de Lyon Examinateur Tanneguy REDARCE Professeur LAI - INSA de Lyon Directeur

Novembre 2005

INSTITUT NATIONAL DES SCIENCES APPLIQUEES DE LYON Directeur : STORCK A. Professeurs : AUDISIO S. PHYSICOCHIMIE INDUSTRIELLE BABOT D. CONT. NON DESTR. PAR RAYONNEMENTS IONISANTS BABOUX J.C. GEMPPM*** BALLAND B. PHYSIQUE DE LA MATIERE BAPTISTE P. PRODUCTIQUE ET INFORMATIQUE DES SYSTEMES MANUFACTURIERS BARBIER D. PHYSIQUE DE LA MATIERE BASTIDE J.P. LAEPSI**** BAYADA G. MECANIQUE DES CONTACTS BENADDA B. LAEPSI**** BETEMPS M. AUTOMATIQUE INDUSTRIELLE BIENNIER F. PRODUCTIQUE ET INFORMATIQUE DES SYSTEMES MANUFACTURIERS BLANCHARD J.M. LAEPSI**** BOISSON C. VIBRATIONS-ACOUSTIQUE BOIVIN M. (Prof. émérite) MECANIQUE DES SOLIDES BOTTA H. UNITE DE RECHERCHE EN GENIE CIVIL - Développement Urbain BOTTA-ZIMMERMANN M. (Mme) UNITE DE RECHERCHE EN GENIE CIVIL - Développement Urbain BOULAYE G. (Prof. émérite) INFORMATIQUE BOYER J.C. MECANIQUE DES SOLIDES BRAU J. CENTRE DE THERMIQUE DE LYON - Thermique du bâtiment BREMOND G. PHYSIQUE DE LA MATIERE BRISSAUD M. GENIE ELECTRIQUE ET FERROELECTRICITE BRUNET M. MECANIQUE DES SOLIDES BRUNIE L. INGENIERIE DES SYSTEMES D’INFORMATION BUREAU J.C. CEGELY* CAVAILLE J.Y. GEMPPM*** CHANTE J.P. CEGELY*- Composants de puissance et applications CHOCAT B. UNITE DE RECHERCHE EN GENIE CIVIL - Hydrologie urbaine COMBESCURE A. MECANIQUE DES CONTACTS COUSIN M. UNITE DE RECHERCHE EN GENIE CIVIL - Structures DAUMAS F. (Mme) CENTRE DE THERMIQUE DE LYON - Energétique et Thermique DOUTHEAU A. CHIMIE ORGANIQUE DUFOUR R. MECANIQUE DES STRUCTURES DUPUY J.C. PHYSIQUE DE LA MATIERE EMPTOZ H. RECONNAISSANCE DE FORMES ET VISION ESNOUF C. GEMPPM*** EYRAUD L. (Prof. émérite) GENIE ELECTRIQUE ET FERROELECTRICITE FANTOZZI G. GEMPPM*** FAVREL J. PRODUCTIQUE ET INFORMATIQUE DES SYSTEMES MANUFACTURIERS FAYARD J.M. BIOLOGIE FONCTIONNELLE, INSECTES ET INTERACTIONS FAYET M. MECANIQUE DES SOLIDES FERRARIS-BESSO G. MECANIQUE DES STRUCTURES FLAMAND L. MECANIQUE DES CONTACTS FLORY A. INGENIERIE DES SYSTEMES D’INFORMATIONS FOUGERES R. GEMPPM*** FOUQUET F. GEMPPM*** FRECON L. REGROUPEMENT DES ENSEIGNANTS CHERCHEURS ISOLES GERARD J.F. INGENIERIE DES MATERIAUX POLYMERES GERMAIN P. LAEPSI**** GIMENEZ G. CREATIS** GOBIN P.F. (Prof. émérite) GEMPPM*** GONNARD P. GENIE ELECTRIQUE ET FERROELECTRICITE GONTRAND M. PHYSIQUE DE LA MATIERE GOUTTE R. (Prof. émérite) CREATIS** GOUJON L. GEMPPM*** GOURDON R. LAEPSI****. GRANGE G. GENIE ELECTRIQUE ET FERROELECTRICITE GUENIN G. GEMPPM*** GUICHARDANT M. BIOCHIMIE ET PHARMACOLOGIE GUILLOT G. PHYSIQUE DE LA MATIERE GUINET A. PRODUCTIQUE ET INFORMATIQUE DES SYSTEMES MANUFACTURIERS

GUYADER J.L. VIBRATIONS-ACOUSTIQUE GUYOMAR D. GENIE ELECTRIQUE ET FERROELECTRICITE HEIBIG A. MATHEMATIQUE APPLIQUEES DE LYON JACQUET-RICHARDET G. MECANIQUE DES STRUCTURES JAYET Y. GEMPPM*** JOLION J.M. RECONNAISSANCE DE FORMES ET VISION JULLIEN J.F. UNITE DE RECHERCHE EN GENIE CIVIL - Structures JUTARD A. (Prof. émérite) AUTOMATIQUE INDUSTRIELLE KASTNER R. UNITE DE RECHERCHE EN GENIE CIVIL - Géotechnique KOULOUMDJIAN J. INGENIERIE DES SYSTEMES D’INFORMATION LAGARDE M. BIOCHIMIE ET PHARMACOLOGIE LALANNE M. (Prof. émérite) MECANIQUE DES STRUCTURES

LALLEMAND A. CENTRE DE THERMIQUE DE LYON - Energétique et thermique LALLEMAND M. (Mme) CENTRE DE THERMIQUE DE LYON - Energétique et thermique LAUGIER A. PHYSIQUE DE LA MATIERE Mai 2003 LAUGIER C. BIOCHIMIE ET PHARMACOLOGIE LAURINI R. INFORMATIQUE EN IMAGE ET SYSTEMES D’INFORMATION LEJEUNE P. UNITE MICROBIOLOGIE ET GENETIQUE LUBRECHT A. MECANIQUE DES CONTACTS MASSARD N. INTERACTION COLLABORATIVE TELEFORMATION TELEACTIVITE MAZILLE H. PHYSICOCHIMIE INDUSTRIELLE MERLE P. GEMPPM*** MERLIN J. GEMPPM*** MIGNOTTE A. (Mle) INGENIERIE, INFORMATIQUE INDUSTRIELLE MILLET J.P. PHYSICOCHIMIE INDUSTRIELLE MIRAMOND M. UNITE DE RECHERCHE EN GENIE CIVIL - Hydrologie urbaine MOREL R. MECANIQUE DES FLUIDES ET D’ACOUSTIQUES MOSZKOWICZ P. LAEPSI**** NARDON P. (Prof. émérite) BIOLOGIE FONCTIONNELLE, INSECTES ET INTERACTIONS NIEL E. AUTOMATIQUE INDUSTRIELLE NORTIER P. DREP ODET C. CREATIS** OTTERBEIN M. (Prof. émérite) LAEPSI**** PARIZET E. VIBRATIONS-ACOUSTIQUE PASCAULT J.P. INGENIERIE DES MATERIAUX POLYMERES PAVIC G. VIBRATIONS-ACOUSTIQUE PELLETIER J.M. GEMPPM*** PERA J. UNITE DE RECHERCHE EN GENIE CIVIL - Matériaux PERRIAT P. GEMPPM*** PERRIN J. INTERACTION COLLABORATIVE TELEFORMATION TELEACTIVITE PINARD P. (Prof. émérite) PHYSIQUE DE LA MATIERE PINON J.M. INGENIERIE DES SYSTEMES D’INFORMATION PONCET A. PHYSIQUE DE LA MATIERE POUSIN J. MODELISATION MATHEMATIQUE ET CALCUL SCIENTIFIQUE PREVOT P. INTERACTION COLLABORATIVE TELEFORMATION TELEACTIVITE PROST R. CREATIS** RAYNAUD M. CENTRE DE THERMIQUE DE LYON - Transferts Interfaces et Matériaux REDARCE H. AUTOMATIQUE INDUSTRIELLE RETIF J-M. CEGELY* REYNOUARD J.M. UNITE DE RECHERCHE EN GENIE CIVIL - Structures RIGAL J.F. MECANIQUE DES SOLIDES RIEUTORD E. (Prof. émérite) MECANIQUE DES FLUIDES ROBERT-BAUDOUY J. (Mme) (Prof. émérite) GENETIQUE MOLECULAIRE DES MICROORGANISMES ROUBY D. GEMPPM*** ROUX J.J. CENTRE DE THERMIQUE DE LYON – Thermique de l’Habitat RUBEL P. INGENIERIE DES SYSTEMES D’INFORMATION SACADURA J.F. CENTRE DE THERMIQUE DE LYON - Transferts Interfaces et Matériaux SAUTEREAU H. INGENIERIE DES MATERIAUX POLYMERES SCAVARDA S. AUTOMATIQUE INDUSTRIELLE SOUIFI A. PHYSIQUE DE LA MATIERE SOUROUILLE J.L. INGENIERIE INFORMATIQUE INDUSTRIELLE THOMASSET D. AUTOMATIQUE INDUSTRIELLE THUDEROZ C. ESCHIL – Equipe Sciences Humaines de l’Insa de Lyon UBEDA S. CENTRE D’INNOV. EN TELECOM ET INTEGRATION DE SERVICES VELEX P. MECANIQUE DES CONTACTS VIGIER G. GEMPPM*** VINCENT A. GEMPPM*** VRAY D. CREATIS** VUILLERMOZ P.L. (Prof. émérite) PHYSIQUE DE LA MATIERE Directeurs de recherche C.N.R.S. : BAIETTO-CARNEIRO M-C. (Mme) MECANIQUE DES CONTACTS ET DES SOLIDES BERTHIER Y. MECANIQUE DES CONTACTS CONDEMINE G. UNITE MICROBIOLOGIE ET GENETIQUE COTTE-PATAT N. (Mme) UNITE MICROBIOLOGIE ET GENETIQUE ESCUDIE D. (Mme) CENTRE DE THERMIQUE DE LYON FRANCIOSI P. GEMPPM*** MANDRAND M.A. (Mme) UNITE MICROBIOLOGIE ET GENETIQUE POUSIN G. BIOLOGIE ET PHARMACOLOGIE ROCHE A. INGENIERIE DES MATERIAUX POLYMERES SEGUELA A. GEMPPM*** Directeurs de recherche I.N.R.A. : FEBVAY G. BIOLOGIE FONCTIONNELLE, INSECTES ET INTERACTIONS GRENIER S. BIOLOGIE FONCTIONNELLE, INSECTES ET INTERACTIONS RAHBE Y. BIOLOGIE FONCTIONNELLE, INSECTES ET INTERACTIONS

Directeurs de recherche I.N.S.E.R.M. : PRIGENT A.F. (Mme) BIOLOGIE ET PHARMACOLOGIE MAGNIN I. (Mme) CREATIS** * CEGELY CENTRE DE GENIE ELECTRIQUE DE LYON ** CREATIS CENTRE DE RECHERCHE ET D’APPLICATIONS EN TRAITEMENT DE L’IMAGE ET DU SIGNAL ***GEMPPM GROUPE D'ETUDE METALLURGIE PHYSIQUE ET PHYSIQUE DES MATERIAUX ****LAEPSI LABORATOIRE D’ANALYSE ENVIRONNEMENTALE DES PROCEDES ET SYSTEMES INDUSTRIELS

2005 SIGLE ECOLE DOCTORALE NOM ET COORDONNEES DU RESPONSABLE

CHIMIE DE LYON Responsable : M. Denis SINOU

M. Denis SINOU Université Claude Bernard Lyon 1 Lab Synthèse Asymétrique UMR UCB/CNRS 5622 Bât 308 2ème étage 43 bd du 11 novembre 1918 69622 VILLEURBANNE Cedex Tél : 04.72.44.81.83 Fax : 04 78 89 89 14 [email protected]

E2MC

ECONOMIE, ESPACE ET MODELISATION DES COMPORTEMENTS Responsable : M. Alain BONNAFOUS

M. Alain BONNAFOUS Université Lyon 2 14 avenue Berthelot MRASH M. Alain BONNAFOUS Laboratoire d’Economie des Transports 69363 LYON Cedex 07 Tél : 04.78.69.72.76 Alain.bonnafous∂ish-lyon.cnrs.fr

E.E.A.

ELECTRONIQUE, ELECTROTECHNIQUE, AUTOMATIQUE M. Daniel BARBIER

M. Daniel BARBIER INSA DE LYON Laboratoire Physique de la Matière Bâtiment Blaise Pascal 69621 VILLEURBANNE Cedex Tél : 04.72.43.64.43 Fax 04 72 43 60 82 [email protected]

E2M2

EVOLUTION, ECOSYSTEME, MICROBIOLOGIE, MODELISATION

http://biomserv.univ-lyon1.fr/E2M2

M. Jean-Pierre FLANDROIS

M. Jean-Pierre FLANDROIS UMR 5558 Biométrie et Biologie Evolutive Equipe Dynamique des Populations Bactériennes Faculté de Médecine Lyon-Sud Laboratoire de Bactériologie BP 1269600 OULLINS Tél : 04.78.86.31.50 Fax 04 72 43 13 88 E2m2∂biomserv.univ-lyon1.fr

EDIIS

INFORMATIQUE ET INFORMATION POUR LA SOCIETE

http://www.insa-lyon.fr/ediis M. Lionel BRUNIE

M. Lionel BRUNIE INSA DE LYON EDIIS Bâtiment Blaise Pascal 69621 VILLEURBANNE Cedex Tél : 04.72.43.60.55 Fax 04 72 43 60 71 [email protected]

EDISS

INTERDISCIPLINAIRE SCIENCES-SANTE http://www.ibcp.fr/ediss

M. Alain Jean COZZONE

M. Alain Jean COZZONE IBCP (UCBL1)

7 passage du Vercors 69367 LYON Cedex 07 Tél : 04.72.72.26.75 Fax : 04 72 72 26 01 [email protected]

MATERIAUX DE LYON http://www.ec-lyon.fr/sites/edml M. Jacques JOSEPH

M. Jacques JOSEPH Ecole Centrale de Lyon Bât F7 Lab. Sciences et Techniques des Matériaux et des Surfaces 36 Avenue Guy de Collongue BP 163 69131 ECULLY Cedex Tél : 04.72.18.62.51 Fax 04 72 18 60 90 [email protected]

Math IF

MATHEMATIQUES ET INFORMATIQUE FONDAMENTALE http://www.ens-lyon.fr/MathIS M. Franck WAGNER

M. Franck WAGNER Université Claude Bernard Lyon1 Institut Girard Desargues UMR 5028 MATHEMATIQUES Bâtiment Doyen Jean Braconnier Bureau 101 Bis, 1er étage 69622 VILLEURBANNE Cedex Tél : 04.72.43.27.86 Fax : 04 72 43 16 87 [email protected]

MEGA

MECANIQUE, ENERGETIQUE, GENIE CIVIL, ACOUSTIQUE http://www.lmfa.ec-lyon.fr/autres/MEGA/index.html M. François SIDOROFF

M. François SIDOROFF Ecole Centrale de Lyon Lab. Tribologie et Dynamique des Systêmes Bât G8 36 avenue Guy de Collongue BP 163 69131 ECULLY Cedex Tél :04.72.18.62.14 Fax : 04 72 18 65 37 [email protected]

mailto:[email protected]


http://biomserv.univ-lyon1.fr/E2M2

http://www.insa-lyon.fr/ediis


http://www.ibcp.fr/ediss


http://www.ec-lyon.fr/sites/edml


http://www.ens-lyon.fr/MathIS


http://www.lmfa.ec-lyon.fr/autres/MEGA/index.html


Gang Chen Thèse INSA de Lyon, LAI 2005 9

Table of Contents

TABLE OF CONTENTS ......................................................................................................... 9

EXTENDED RESUME (IN FRENCH) ................................................................................. 13

INTRODUCTION ................................................................................................................ 21

CHAPTER 1 FROM THE PROBLEM OF COLONOSCOPY TO THE SOLUTION OF

ROBOTIC COLONOSCOPY ............................................................................................... 25

1.1 Introduction to the colonoscopy .............................................................................. 27

1.1.1 Colon Cancer ................................................................................................... 27

1.1.2 Colorectal cancer screening .............................................................................. 29

1.1.3 Colonoscopy .................................................................................................... 33

1.1.4 Colonoscope..................................................................................................... 34

1.1.5 The colonoscopy examination .......................................................................... 37

1.1.6 Drawbacks of conventional colonoscopy .......................................................... 38

1.1.6.1 Complexity of the procedure for the surgeon ................................................. 38

1.1.6.2 The pain and discomfort for the patient ......................................................... 39

1.2 Overview of current efforts on the automation of colonoscopy (state of the art of

robotic colonoscopy) ....................................................................................................... 39

1.2.1 Locomotion mechanism.................................................................................... 40

1.2.1.1 Snake-like locomotion .................................................................................. 40

1.2.1.2 Inchworm locomotion mechanism ................................................................. 43

1.2.1.3 Autonomous capsules.................................................................................... 48

1.2.2 Steerable distal end .......................................................................................... 49

1.2.3 Conclusions...................................................................................................... 53

1.3 Conclusions and our solution .................................................................................. 54

CHAPTER 2 DESIGN AND CONSTRUCTION OF A MICRO-ROBOTIC

MANIPULATOR FOR COLONOSCOPY............................................................................ 55

2.1 General Introduction ............................................................................................... 57


2.2 Continuum robots ................................................................................................... 59

2.2.1 Backbone-based extrinsic continuum robot....................................................... 60

2.2.2 Fluid/pneumatic power driven intrinsic continuum robot .................................. 61

2.2.3 Hybrid continuum robot ................................................................................... 65

2.2.4 The key advantage of continuum robot compared with discrete manipulator ..... 66

2.3 Design of EDORA II............................................................................................... 68

2.3.1 Introduction...................................................................................................... 68

2.3.2 Previous works on robotic colonoscopy in the project of the laboratory ............ 70

2.3.3 The problems and shortcomings of EDORA ..................................................... 73

2.3.4 Construction of EDORA II ............................................................................... 74

2.3.5 Discussions and Conclusions ............................................................................ 78

2.4 Control system for EDORA II ................................................................................. 79

2.5 Conclusion.............................................................................................................. 81

CHAPTER 3 KINEMATICS ANALYSIS FOR CONTINUUM ROBOTIC

MANIPULATOR: EDORA II ............................................................................................... 83

3.1 Three essential parameters characterize the deflected shape of EDORA II............... 85

3.2 Kinematics analysis using basic geometry ............................................................... 88

3.2.1 Basic geometry for kinematic analysis.............................................................. 88

3.2.2 Derivation of orientation angle of the bending plan .......................................... 89

3.2.3 Derivation of bending angle α .......................................................................... 90

3.2.4 Summary .......................................................................................................... 91

3.3 Derivation of kinematics relating to internal pressure of each chamber ................... 91

3.3.1 The experiment setting and results.................................................................... 92

3.3.2 Relationship between deflected shape with relation to the applied pressure of

each chamber ............................................................................................................... 93

3.4 Velocity Kinematics ............................................................................................... 94

3.4.1 Non-redundant case .......................................................................................... 95

3.4.2 Redundant case ................................................................................................ 95

3.5 Inverse velocity kinematics ..................................................................................... 96

3.6 Validation of kinematic model ................................................................................ 98

3.6.1 The sensor choice and experimental setup ........................................................ 99

3.6.1.1 The miniBIRD ........................................................................................... 99

3.6.1.2 Experimental setup ................................................................................... 100


3.6.2 Validation of bending angle............................................................................ 101

3.6.3 Validation of orientation angle ....................................................................... 103

3.6.4 Verification of correlation among each chamber............................................. 105

3.6.5 Estimation of a correction parameter .............................................................. 106

3.7 Conclusions .......................................................................................................... 109

CHAPTER 4 DYNAMICS ANALYSIS AND PARAMETERS IDENTIFICATION ........ 111 4.1 Dynamic analysis of EDORA II system ..............................................................................113

4.1.1 Electro-pneumatic part ................................................................................... 114

4.1.2 Mechanical part:............................................................................................. 115

4.1.2.1 Static behavior of EDORA II .......................................................................................... 115

4.1.2.2 Dynamics of EDORA II .................................................................................................. 117

4.1.3 The whole system........................................................................................... 117

4.2 Parameter identification of dynamic behavior of EDORA II ..............................................118

4.2.1 Introduction to identification of continuous-time system ................................ 118

4.2.2 Formulations of parameter estimation of continuous-time Model .................... 119

4.2.3 Levenberg-Marquardt algorithm and its numerical implementation................. 121

4.3 Experiment design for identification and its validation......................................................122

4.3.1 Experiment setting ......................................................................................... 123

4.3.2 Data collection ............................................................................................... 123

4.3.3 Estimation results and its analysis .................................................................. 125

4.3.4 Validation of identification results.................................................................. 130

4.4 Conclusions ......................................................................................................................131

Erreur ! Aucune entrée de table des matières n'a été trouvée.

CONCLUSION AND PERSPECTIVES ............................................................................. 151

REFERENCES .................................................................................................................... 155

FOLIO ADMINISTRATIF ................................................................................................. 169

Remerciements

Ce travail a été réalisé au Laboratoire d'Automatique Industrielle de l'INSA de Lyon

dans l’équipe robotique médicale sous la codirection de Monsieur Tanneguy Redarce et Monsieur Minh Tu Pham.

Je souhaite adresser mes plus sincères remerciements à Monsieur Tanneguy Redarce, Directeur du Laboratoire d'Automatique Industrielle, Professeur à l'INSA de Lyon, de m'avoir donné l’opportunité de travailler au sein de son équipe et de m'avoir dirigé pendant cette thèse. En particulier, je le remercie pour ses encouragement, son soutien, sa disponibilité et sa générosité tout au long de ce travail.

Je tiens également à adresser mes remerciements à mon co-directeur de thèse, Monsieur Minh Tu Pham, maître de conférences à l'INSA de Lyon pour avoir su me guider avec attention et une gentillesse constante. Ses qualités scientifiques et humaines mais aussi ses encouragements ont largement contribué à l’aboutissement de cette thèse.

J'adresse mes remerciements à Monsieur Phillipe Bidaud, Directeur du Laboratoire de Robotique de Paris, de m'avoir fait l'honneur de présider mon jury de thèse. Je tiens à remercier Monsieur Michel de Mathelin, Professeur au LSSIIT (ENSP Strasbourg), et Monsieur Yacine Amirat, Professeur au LISSI (Université Paris XII), pour avoir accepté la responsabilité d'être rapporteurs du présent mémoire et pour leur participation au jury. Leurs remarques et questions pertinentes m'ont été très précieuses

J'adresse mes remerciements aussi à Monsieur Maurice Bétemps, Professeur au Laboratoire d'Automatique Industrielle de l'INSA de Lyon, pour ses encouragements et son soutien au début de ma thèse. Je le remercie vivement d’avoir accepté de participer à mon jury de thèse.

Je souhaite remercier à Christine Prelle et Frédéric Lamarque pour le travail effectué en partie à l'Université Technologique de Compiègne, et en partie avec nous, au laboratoire.

Je remercie également Guillaume de m’avoir beaucoup aidé pendant au début de mon séjour en France, il m'a permis de m’installer très rapidement et m’intégrer au sein du projet. De plus, je le remercie d’apporter sa contribution au travail de coloscopie.

Je tiens à remercier Cherif, Juan-carlos pour leur contribution à la réalisation des prototypes et des essais effectués lors de leur projet de fin d’études d’ingénieur et stage de Master.

Je tiens à remercier spécialement Patrick et Christophe pour l'aide technique qu'ils m'ont apportée, chacun dans leur domaine respectif. Je me dois de remercier sincèrement Maguy pour son soutien et sa disponibilité.

Je souhaite remercier plus particulièrement mes collègues de laboratoire de longues dates, Chafik, Ruimark, Mohamed, Gerardo, Richard, Rosario, Oualid, Bogdan et Osama, pour nos échanges quotidiens et pour leurs soutiens.

Je tiens remercie à tous les membres du laboratoire qui ont eu à me supporter (Eric Bideaux, Xavier Brun, Willy Marquis-Favre, Sylvie Sesmat, Jean-Pierre Simon, Daniel Thomasset, Eric Niel, Laurent Pietrac, Corinne).

Je remercie également toute mes amis chinois en France et en Chine, Wu Tong, Han Bing, Xu Xin, Wei Yu et Xu De, Yang Guosheng, Cao Zhiqiang, Wang Shuo ...

Enfin, je souhaite remercier à ceux qui m'ont encouragé depuis toujours : mes parents et ma famille.

Gang CHEN Thèse INSA de Lyon, LAI 2005 13

Résumé étendu

Depuis les 20 dernières années, la robotique est de plus en plus acceptée comme une solution

viable à beaucoup d'applications dans la chirurgie, en particulier dans le domaine de la chirurgie

assistée par ordinateur (Computer Aided Surgery), de la Chirurgie Mini-Invasive (Minimally Invasive

Surgery) et de la Thérapie Mini-Invasive (Minimally Invasive Therapy). D’une manière générale, la

robotique médicale permet d’améliorer la précision des gestes des médecins et les aide à exécuter des

procédures chirurgicales innovantes. Les avantages cliniques qui en découlent sont nombreux :

• Amélioration de l'efficacité de la thérapie et du diagnostic;

• Amélioration de la sûreté des patients et du chirurgien;

• Amélioration du confort du patients (moins blessé et moins de traumas);

• Réduction des coûts.

Cependant, nous ne sommes qu’au début de l'introduction de la robotique dans le monde de la

médecine car la première application médicale d’un robot remonte à 1985. A l’époque, un robot

industriel PUMA 560 a été utilisé pour placer une aiguille dans le cadre de la biopsie d’un cerveau.

Puis, les groupes de recherche en Europe, en Asie et aux Etats-Unis ont commencé à étudier des

applications médicales de la robotique. Ainsi beaucoup de systèmes robotisés comme ROBODOC

pour la chirurgie de hanche, CASPAR pour le remplacement du genou ont été développés. En 1994,

AESOP, système pour la Chirurgie Mini-Invasive, est le premier produit commercial ayant obtenus

l'approbation de la FDA. Il existe actuellement beaucoup de recherche sur la robotique médicale à

travers plusieurs secteurs cliniques, tels que l’ophtalmologie, la laparoscopie, l'urologie, etc. Plusieurs

articles de synthèse importants sur la robotique dans la chirurgie ont été écrits. [DAVIES 00 ] décrit

l'histoire de la robotique chirurgicale et donne une classification des systèmes robotisés. [TROCCAZ

03] effectue un tour d’horizon historique et décrit les systèmes robotisés passifs, semi-actifs, et actifs.

[TAYLOR 03] se concentre sur le rôle des robots médicaux dans les systèmes de Chirurgie Assistée

par Ordinateur. Les systèmes sont classifiés en tant que deux grandes familles : CAD/CAM chirurgical

et aides aux gestes chirurgicaux. [DARIO 03] fait un état de l’art des outils chirurgicaux et des

dispositifs courants pour la chirurgie assistée par ordinateur.

En tant qu'outils de recherche efficace et de validation, les robots industriels sont encore

utilisés en chirurgie intégrée par ordinateur en raison de leur robustesse et leur disponibilité. Le robot


est commandé par un système informatique qui lui permet de déplacer l’organe terminal en n'importe

quels points et orientations désirés dans sa zone de travail. Ce genre de robot est conforme à la

définition de l'institut robotique d'Amérique, un robot est "un manipulateur reprogrammable et

multifonctionnel conçu pour déplacer des matériaux, des pièces, des outils, ou d'autres dispositifs

spécialisés par divers mouvements programmés pour l'exécution d'une variété de tâches". D'autre part,

les robots médicaux doivent coopérer avec l'humain (chirurgien et personnel) et agir sur les patients.

Des problèmes de sûreté et de stérilisation doivent être considérés comme des impératifs techniques

spéciaux et stricts pour des robots sous environnement non structurés avec des contraintes dures,

particulièrement pour les dispositifs médicaux actifs telles que la laparoscopie et la coloscopie. Bien

que quelques chercheurs aient commencé à concevoir de nouveaux robots médicaux, ces robots

doivent toujours être améliorés en vue de l'application commerciale. En outre, puisque chaque

opération chirurgicale possède des conditions et contraintes spécifiques, des robots dédiés à la tâche

doivent donc être conçus pour répondre aux exigences de la discipline médicale (la laparoscopie, la

coloscopie, etc…).

Ce travail de thèse a pour objet de répondre à ce besoin par la recherche de solutions

innovantes pour la conception, la modélisation et la commande d’un micro-robot semi-autonome

pouvant servir de coloscope. Pour aboutir à ce but, deux aspects de recherche ont été abordés :

• Les contraintes et les limites des coloscopes actuellement utilisés, nous ont amené à chercher des

matériaux qui sont particulièrement adaptés pour la conception de la partie distale de coloscope.

La principale difficulté de cette approche réside alors dans l’étude et la compréhension du

comportement de ces matériaux qui présentent très souvent un caractère non linéaire avec un

hystérésis.

• Pour le guidage automatique de la progression du coloscope dans le colon, une planification de la

trajectoire de la structure doit être envisagée avec sa propre loi de commande pour limiter les

contacts avec la paroi du colon. Pour ce but, la recherche d’une intégration optimale de capteurs

dans le micro-robot est un important aspect de ce travail de thèse.

Le chapitre 1 présente les problèmes et les difficultés spécifiques de la coloscopie du point de

vue du clinicien et notre solution à répondre aux besoins et faciliter la manœuvre du coloscope grâce à

la conception d’un nouveau micro système « robotisé ».

Le cancer du colon est un problème important de la santé publique dans beaucoup de pays. En

France, on estime à 37 000 le nombre de nouveaux cancers colorectaux diagnostiqués [PIENK 01] par

an. Ces cancers occupaient la seconde place après le cancer du poumon chez les hommes et après le


cancer du sein chez les femmes. Avec 16 000 décès annuels, les cancers du colon et du rectum

constituent la seconde cause de décès par cancer, tous sexes confondus. Aux Etats-Unis, le cancer du

colon est le deuxième principal cancer tueur parmi les hommes et les femmes derrière le cancer du

poumon. En 2005, 104 950 nouveaux cas de cancer colorectal seront diagnostiqués et 56 290 mourront

de cette maladie. En Chine, les taux d'incidence du cancer du colon avaient rapidement augmenté dans

de grandes villes ces dernières années. Le risque de développer le cancer du colon est augmenté pour

les personnes de plus de 50 ans, et pour ceux qui ont des antécédents de cancer du côlon dans leur

famille.

Il existe plusieurs moyens de détection qui peuvent être utilisés pour diagnostiquer un cancer :

Le test Hemoccult II, le toucher rectal, l’examen radiologique, la coloscopie virtuelle, la

sigmoidoscopie et la coloscopie. Mais la coloscopie reste le seul examen fiable à l’heure actuelle. Les

chirurgiens en pratiquent chaque année un million dans les établissements de soins français.

La coloscopie est l’examen qui permet de visualiser l’intérieur de tout le colon à l’aide d’un

endoscope long et souple. Dans ce cas, il est appelé coloscope. Sa taille est de 1.6 m a 2 m de long

pour environ 13 mm de diamètre. L’examen de coloscopie dure environ 30 minutes, dont 10 minutes

de mise en place de tout l’endoscope dans le colon. Le coloscope est introduit par l’anus, puis

l’appareil est dirigé sans forcer, sous contrôle de la vue jusqu’au caecum en orientant manuellement la

tête de l’outil à l’aides des deux molettes (le béquillage).

C’est un examen endoscopique qui demande de la technique, et il est très impopulaire chez les

patients. C’est pour cela que le simple fait de bouger le coloscope dans le colon requiert des années de

pratique et d’entraînement. L’opération de coloscopie peut être séparée en deux types de mouvements

qui peuvent être facilement dissociables : Le mouvement de locomotion et celui d’orientation de la

partie distale de l’outil. C’est probablement en raison des ces différents problèmes de manipulation

que beaucoup de recherches ont commencé ces dernières décennies. Ces deux aspects sont également

abordés séparément pour l’amélioration de la procédure de coloscopie pour automatiser les

mouvements. Les problèmes de locomotion concernent surtout l’activation, l’alimentation des

actionneurs et la commande de leurs séquences. Quant à l’extrémité inclinable de l’outil, qui est

généralement actionnée par un ou deux câbles, les difficultés majeures sont son activation à distance et

les difficultés pour négocier les courbes du colon sans déchirer sa paroi.

De nombreux laboratoires dans le monde se préoccupent de l’amélioration des conditions de

coloscopie, que ce soit en Belgique, en Chine, en Corée, aux Etats-Unis, et en Italie, des recherches

sont déjà très avancées dans ce domaine. Jusqu’à présent, deux types de travaux se concentrent sur la


conception de nouveaux instruments médicaux pour la coloscopie. La première approche, appelée

“progression autonome”, vise à changer complètement l’examen du colon. Au lieu d’insérer le

coloscope dans le colon par le chirurgien, les nouveaux systèmes ont la capacité de se propulser de

manière autonome ou semi-autonome dans le colon. Ces systèmes sont soit des robots de type « snake-

like robot », soit de type inchworm. En ce qui concerne la progression autonome, le solution la plus

utilisée est de concevoir un robot inchworm ou des capsules instrumentées. Les robots inchworm sont

fabriqués avec des soufflets, et ils travaillent principalement en compression et en élongation pour

réaliser la progression dans le colon. Mais, pour ce type de robot, les contacts avec les parois

intestinales semblent a priori indispensables et des problèmes de glissement sont souvent mis en

avant. L’autre approche consiste à développer des nouveaux instruments, visant à augmenter la

dextérité du coloscope traditionnel en ajoutant un degré de liberté dans la tête de l’outil. Cette

approche nécessite de concevoir une nouvelle tête inclinable pour faciliter l’insertion dans l’intestin et

passer les courbures tandis que le déplacement est encore effectué par le chirurgien.

Au LAI, en collaboration avec le Professeur Thierry Ponchon, gastro-entérologue à l’hôpital

Edouard Herriot, nous avons proposé une nouvelle structure robotique permettant d’améliorer les

condition d’intervention en coloscopie. Effectivement, ces spécialistes insistent sur le fait que de trop

nombreux préjudices sont causés aux parois intestinales lors de cette intervention. Celle-ci consiste à

explorer l’intérieur du colon pour confirmer un diagnostic ou, plus fréquemment, pour intervenir en

cas de détection préalables d’anomalies pouvant évoluer en cancer. Ces discussions et les

inconvénients de la progression autonome nous ont orienté vers la conception et la réalisation d’une

tête de coloscope intelligente, la progression du coloscope dans l’intestin étant gardée par le

chirurgien. Notre étude se situent donc au niveau de la complexité de l’opération, et du confort du

patient : intervention de moins longue durée, rétablissement plus rapide, diminution du risque de

perforation intestinale et par conséquent, coût sociétal global moindre.

Suite à la présentation détaillée des besoins en coloscopie au premier chapitre, nous

présentons la conception d’un micro-robot, EDORA II (Extrémité Distale à ORientation

Automatique) dans le chapitre 2. Le concept de « robot continuum » est tout d’abord introduit. Ce

type de robot ne contient pas d’articulations discrètes à la différence des robots industriels classiques.

Une étude bibliographique présente ensuite un état de l’art sur les dispositifs de type « robot

continuum ». Trois exemples de robots sont présentés et comparés selon le type d’actionnement et le

matériau de la structure : « Cable-driven continuum robot », « Fluid/pneumatic power driven

continuum robot » et « hybrid continuum robot ». La conception et la réalisation de ces robots sont

inspirées par de mouvements de certains organes d’animaux telles que la langue, la trompe d’éléphant


etc. Quant au robot continuum à câbles, il est généralement constitué d’une colonne vertébrale qui

supporte la structure avec deux ou trois câbles utilisés pour l’actionnement du robot.

Une autre solution d’actionnement est d’utiliser l’énergie d’un fluide sous pression (eau ou

air). La conception de ce genre de robot intègre la structure de soutien et l’actionneur dans une seule

unité. Beaucoup de recherches s’intéressent à cette solution parce que cette structure produit un

mécanisme simple, compact et léger et génère des mouvements dans l’espace. Les matériaux souvent

utilisés pour construire l’actionneur sont les soufflets métalliques, le caoutchouc, ou des matériaux tels

que le silicone, qui peuvent s’allonger aisément sous la variation de pression d’un fluide. Avec la

combinaison de trois actionneurs et les contraintes de la structure, le robot peut alors se fléchir dans

l’espace. Ce comportement de robot continuum peut être utile pour des applications telles que la

préhension, l’exploration tubulaire et l’inspection de l’endoscope.

Dans cette thèse, le travail avait pour objectif prioritaire l’amélioration de l’actionneur

EDORA (Extrémité Distale à Orientation Automatique) de la thèse [THOMANN 2003b]. Pour des

raisons principalement de commodité de tests, de facilité de modification et d'usinage, une maquette

de faisabilité de la tête de coloscope à l'échelle 2 avait été réalisée. Il a été choisi de concevoir et de

fabriquer un actionneur à l'aide de soufflets métalliques standard actionnés par l’énergie pneumatique.

Pour la maquette de faisabilité, des capteurs à effet Hall et un aimant permanent ont pu être utilisés. La

maquette de faisabilité avait pour objectif de tester la capacité de l'EDORA à se repositionner

automatiquement au milieu d'un cercle représentant les parois d'un tube. La maquette de faisabilité a

permis d’observer les performances en boucle fermée de l’actionneur à des mouvements de

perturbation de sa base. Les capteurs à effet Hall n’étant pas transposable pour faire progresser l’outil

dans un tuyau, des fibres optiques ont été intégrés à son extrémité. A cause de sa limitation en

inclinaison, la progression de l’actionneur EDORA a été testée dans un tube de faible

courbure simulant les parois de l’intestin. Les résultats obtenus étaient encourageants car l’EDORA ne

vient jamais en contact avec les parois du tuyau, tout au long de sa progression.

Bien que les expériences préliminaires aient prouvé que l’EDORA possédaient un

comportement satisfaisant [THOMANN 03b], les expériences ont également démontré des faiblesses à

améliorer.

1. EDORA peut seulement garantir un angle de flexion de 23° maximum.

2. Par ailleurs, le diamètre de l’EDORA est 26mm, ce qui est deux fois plus grand que la taille d’un

coloscope classique (12.8 mm). Par conséquent, les recherches préliminaires effectuées ont


rapidement montré les difficultés à miniaturiser les actionneurs pour réaliser un nouveau prototype

(Bien que [BAILLY 04] ait réalisé un micro-robot MALICA de 5mm de diamètre).

3. De même, des problèmes de miniaturisations sont rencontrés pour le choix des capteurs de

distance.

Pour permettre une réduction importante de la taille de l’EDORA, nous avons pensé à

plusieurs possibilités :

• utiliser à nouveau des soufflets métalliques de taille réduite

• considérer une nouvelle structure et utiliser de nouveau matériaux

• envisager d’utiliser un coloscope existant, en motorisant les axes des molettes utilisées

manuellement par le chirurgien pour incliner la tête de l’outil.

Inspiré par les actionneurs souples en silicone fabriqué par [SUZUMORI 90] et après beaucoup

d’essais sur plusieurs prototypes, nous avons conçu et fabriqué un nouveau prototype expérimental en

silicone possédant trois chambres déformables cylindriques placées à 120° les une des autres et un

orifice central cylindrique, permettant le passage de tous les câbles d’alimentation et des outils

chirurgicaux. Ce prototype, appelé EDORORA II, mesure 17mm de diamètre pour 100 mm de long.

Des servovalves sont utilisées pour faire varier la pression dans les chambres. Pour mesurer la

distance, les capteurs doivent être intégrés dans la structure du prototype. Nous avons donc ajouté

entre chaque chambre une chambre supplémentaire, ces chambre ajoutées ne seront pas mises sous

pression mais elles ont pour rôle principal la diminution de la matière entre les trois chambres initiales

et l’espace du capteur. Il est possible d’atteindre avec l’EDORA II une courbure de près de 120° en

soumettant une chambre déformable à une pression relative de 2 bars.

Le troisième chapitre concerne la modélisation géométrique de l’EDORA II. Du fait de sa

conception, EDORA II est un nouveau type de micro-robot : style continuum. Puisqu’il ne possède ni

de liaisons discrètes ni de corps rigides à l’image des robots industriels, les approches classiques de

modélisation qui s’appliquent habituellement pour la robotique, e.g. le formalisme de Denavit-

Hartenberg, ne peuvent être utilisées pour de tels systèmes. Dans cette thèse, nous avons établi un

modèle directe s’appuyant sur la déformation géométrique de l’actionneur. Le modèle direct d’un

robot correspond classiquement à la formulation des relations exprimant la position de l’organe

terminal du robot en fonction de ses coordonnées généralisées. Pour l’EDORA II, trois paramètres

sont choisis pour caractériser les déplacements du robot ; ce sont : l’angle d’inclinaison de la

terminaison supérieure, l’orientation du plan de courbure et la longueur du prototype.


Pour établir le modèle géométrique, les hypothèses suivantes ont être posées :

• les effets de l’environnement ne sont pas pris en compte,

• le rayon de courbure de l'EDORA II est un arc de cercle constant.

Avec ces hypothèses, un nouveau modèle statique direct est proposé pour représenter la pose de la

terminaison supérieure de l’EDORA II par rapport à sa base.

Pour connaître la longueur de la chambre en fonction de la pression dans celle-ci, le

comportement de l’actionneur doit être caractérisé. Les études précédentes sur les robots utilisant les

soufflets supposent que l’élongation de l’actionneur est proportionnelle à la pression dans la chambre.

Dans un premier temps, une caractérisation statique entre la pression à l’intérieur d’une chambre et

l’élongation du manipulateur est effectuée. Les essais sur chacune des chambres ont permis de

déterminer un comportement non linéaire de l’actionneur, un modèle statique reposant sur une

interpolation polynomiale est donc proposé pour rendre compte de ce phénomène.

Afin de valider les modèles directs, un capteur électromagnétique 3D, miniBIRD

d’Ascenssion Technology, est utilisé pour mesurer l’angle d’inclinaison et l’angle d’orientation. Les

résultats comparatifs ont démontré que le modèle géométrique direct de chaque chambre proposé

reproduit de manière fidèle leur comportement statique.

Cependant, le principe de l’EDORA II est que les trois chambres travaillent ensemble pour

obtenir les déplacements de la partie supérieure de l’EDORA II. Un essai complexe est effectué dans

ce but. Trois signaux sinusoïdaux avec 120° de décalage sont utilisés pour faire faire un tour autour de

l’axe vertical de l’EDORA II. Des différences significatives entre le modèle géométrique et les

résultats expérimentaux sont mises en évidence. Cette différence met en évidence un couplage entre

les différentes chambres. On propose donc dans cette thèse d’étendre le modèle géométrique

classiquement trouvé dans la littérature en rajoutant de nouveaux paramètres qui permettent de tenir

compte du couplage entre les chambres. Ces paramètres de recalage sont obtenus par une optimisation

en minimisant l’écart entre les coordonnées opérationnelles mesurées par le miniBIRD et les

coordonnées opérationnelles obtenues par simulation du modèle géométrique. Le modèle différentiel

de l’EDORA II est ensuite établi à partir des équations du modèle direct. Une étude sur le modèle

différentiel inverse permet de concevoir la commande en orientation de l’EDORA II.

L’objectif principal de cette thèse est la conception d’un nouveau micro-robot pouvant

automatiquement repositionner la tête d’un coloscope au cours de la progression tout en minimisant

l’interaction avec l’environnement. Le chapitre 4 traite du modèle dynamique e l’EDORA II dans


l’objectif de synthétiser une loi de commande dynamique. Le système est décomposé en trois sous

systèmes indépendants, un pour chaque chambre. Chaque sous-système contient deux parties : une

partie electro-pneumatique et une partie mécanique. Les trois sous systèmes peuvent être considérés

comme des systèmes linéaires quand les trois actionneurs travaillent avec de petits déplacements. Les

ordres des modèles dynamiques de chaque partie sont obtenus par l’expérimentation. Pour déterminer

les paramètres intervenant dans le modèle dynamique, la méthode du modèle est choisie. A l’aide de

l’algorithme de Levenberg-Marquardt, l’estimation des paramètres des trois sous systèmes est obtenue

à partir de données expérimentales. Une analyse fréquentielle et une étude de robustesse nous ont

permis de valider ce modèle. La comparaison entre le diagramme de Bode du modèle et celui du tracé

point par point en fréquences du système montre que les modèles dynamiques des chambres sont

conformes au comportement du système.

Le modèle dynamique obtenus de l’EDORA II dans le chapitre 4 nous a permis de

concevoir une loi de commande pour l’asservissement en position. Pour cela, trois capteurs à

fibres optiques sont choisis pour mesurer la distance entre EDORA II et la paroi d’un tube

faisant office de « colon ». L'intégration des capteurs dans l’EDORA II nous permet de mettre

en œuvre un contrôleur simple. Les caractéristiques physiques des capteurs ont été établies et

leur modèle statique est utilisé pour synthétiser un correcteur avance-retard de phase. Pour la

validation expérimentale du correcteur proposé, nous avons utilisé une base mobile pour imiter

les mouvements transversaux lors de l’avance du coloscope dans l’intestin. Pour cela, une table

XY (deux translations découplées) est mise en place sur une course de 24mm dans les deux

directions. Cette plate-forme nous permet de vérifier que l’EDORA II peut rester au centre d’un

tube représentant le colon en dépit des mouvements de la base de l’actionneur. Les résultats

expérimentaux montrent que ce contrôleur possède de bonnes capacités de rejet de

perturbations. Des expériences sont finalement réalisées dans un tube avec une courbure de

100°. Les résultats expérimentaux indiquent que l’EDORA II peut traverser facilement une

grande courbure de 100° sans toucher les parois. Dans le même temps, il est également montré

que notre élément distal peut effectuer un déplacement dans une grande courbure en se

déplaçant par petits déplacements.


Introduction

In the last 20 years, robotics has increasingly become accepted as a viable solution to

many applications in surgery, particularly in the field of computer assisted surgery (CAS) and

minimally invasive surgery and therapy (MIS and MIT). Medical robotics has tremendous

potential for improving the precision and capabilities for physicians to perform surgical

procedures. There are also other clinical advantages:

• To improve the efficiency of therapy and diagnostics;

• To improve the safety of patients and surgeons;

• To improve the comfort of patients( to reduce pain and trauma);

• To reduce the costs.

However, we are just at the beginning of this application of robotics in medicine, with

the first recorded medical application of robots occurring in 1988 [KWOH 88]. In this case, a

PUMA 560 industrial robot was used to position a needle for biopsy of the brain. Then, research

groups in Europe, Asia, and the United States began investigating medical applications of

robotics. Thus many robot systems like ROBODOC system [developed by Integrated Surgical

Systems ] for hip surgery, CASPAR system [developed by OrtoMaquet ] for knee replacement

had been developed. Then in 1994, AESOP system [developed by Compute Motions ] for

minimally invasive surgery, the first commercial product with FDA (Federal Drug

Administration of USA) approval, had been produced for clinical use by Computer Motion Inc.

in the US. Besides this key robotic system, a lot of research is being carried out in the field of

medical robotics across several clinical areas such as opthamology, larporoscopy, urology, etc.

Several important review articles on medical robotics in surgery have been written. [DAVIES

00] describes the history of surgical robotics and gives one classification for different types of

robot systems. [TROCCAZ 03] gives a historical review and describes passive, semi-active, and

active robotic systems. [TAYLOR 03] focuses on the role of medical robots within the context


of Computer-Integrated Surgery (CIS) systems. These systems are classified as two broad

families: surgical CAD/CAM and surgical assistants. At the same time, [DARIO 03], focuses on

surgical tools by highlighting the intelligence and augmenting capabilities of some current

instruments and devices for computer-assisted surgery.

As an effective research and validation tool, industrial robots are still being used in

most computer-integrated surgery because of their robustness and availability. These robots

consist of nearly rigid links that are connected with joints that allow relative motion from one

link to another [CRAIG 89]. Attached to the end of the links is the robot hand, usually referred

to as the end-effector. The robot is controlled by a computer system that is used to move the

end-effector to any desired point and orientation within its workspace. This kind of robot is

conformed to the definition by the Robotic Institute of America. A robot is "a reprogrammable,

multifunctional manipulator designed to move materials, parts, tools, or other specialized

devices through various programmed motions for the performance of a variety of tasks.” At the

same time, medical robots need to cooperate with humans (surgeon and staff) and interact with

the patients. The Safety and sterilization aspects should be considered as well as the special and

strict technical requirements for robots in unstructured environments with harsh constraints,

especially for active medical devices such as laparoscopy and colonoscopy.

Although some researchers have begun to design new medical robots, these robots still

need to be improved for commercial application. In addition, since every surgery has its specific

requirements and constraints, specially-designed robots should be conceived to meet the

requirements of specific surgical task.

In this dissertation, we focus on the application of robots in colonoscopy with special

constraints. Increasingly, colon cancer has become a medical concern in the world, especially in

developed countries, such as USA, Japan and Western Europe. According to the National

Cancer Institute [NCI ], cancers of the colon are the fourth most commonly diagnosed cancers

and rank second among cancer deaths in the United States. However, most colon cancers can be

cured if detected at their early stages. This has lead medical experts to predict that the death toll

due to colon cancer could drop by 50 % to 75% with mass screening of the population.

Unfortunately, due to pain and discomfort experienced by the patient, colonoscopy is especially

unpopular. To improve this procedure, we’ll discuss our work on designing an automatic micro-

robotic manipulator which will replace the bendable tip of the traditional colonoscope.

In chapter 1, the specific problems and difficulties of conventional colonoscopy are

presented from the clinical point of view and then the corresponding efforts which aim to


facilitate the maneuver and lessen the pain to the patient by using robotic technology are

explained in details. Based on this analysis and the surgeon’s suggestions, the solution that we

put forward is that a novel automatic robotic manipulator will be constructed to guide the

advancement of colonoscopy which is kept for the physician.

Then in chapter 2, a new classification of robot without rigid joints, also called

Continuum Robot, which is different from the conventional rigid-link robot, is firstly

introduced. Based on the analysis of related work on the continuum robot, the design of a new

flexible robotic manipulator called EDORA II will be described in detail according to clinical

and technical requirements.

Unlike conventional robots, the continuum robotic manipulators don’t have link joints,

thus rendering the application of the Denavit-Hartenberg, method used in kinematics for discrete

robots, impossible. In this way, a new problem arises: how to build the kinematics of these

manipulators? In chapter 3, we will present a different kinematic model based on the geometric

deformation and its validation for EDORA II.

In view that our final objective is to test the performance of EDORA II in the colon-

like tube, chapter 4 will deal with the dynamic behavior of EDORA II from an experimental

perspective. After the determination of the dynamic model of the linear part of each chamber of

EDORA II, its parameters will be estimated by system identification methods and will be

validated.

The last chapter will deal with test experiments in a tube with a 100° bend by using the

corresponding controller. Position sensors will be chosen and integrated into EDORA II. After

the calibration of the model of the sensor, the dynamic performance of EDORA II will be

studied and a controller will be designed and implemented. For the test in the tube, a path

planning algorithm will be conceived to generate the desired position for each controller during

the insertion process. Then experimental results will be done to see if EDORA II demonstrates

the expected performance.

Finally, the conclusion in the last chapter concerning the work done in this dissertation

as well as some recommendations for future work will be given.

Chapter 1 From the problem of colonoscopy to the solution of robotic colonoscopy


Chapter1

From the problem of colonoscopy to the

solution of robotic colonoscopy



1 CHAPTER 1 FROM THE PROBLEM OF COLONOSCOPY TO THE SOLUTION OF ROBOTIC

COLONOSCOPY ............................................................................................................................................... 25

1.1 Introduction to the colonoscopy........................................................................................................ 27

1.1.1 Colon Cancer............................................................................................................................. 27

1.1.2 Colorectal cancer screening....................................................................................................... 29

1.1.3 Colonoscopy.............................................................................................................................. 33

1.1.4 Colonoscope.............................................................................................................................. 34

1.1.5 The colonoscopy examination................................................................................................... 37 1.1.6 Drawbacks of conventional colonoscopy .................................................................................................. 38

1.1.6.1 Complexity of the procedure for the surgeon........................................................................ 38

1.1.6.2 The pain and discomfort for the patient ................................................................................ 39

1.2 Overview of current efforts on the automation of colonoscopy (state of the art of robotic

colonoscopy) ................................................................................................................................................. 39

1.2.1 Locomotion mechanism ............................................................................................................ 41 1.2.1.1 Snake-like locomotion .......................................................................................................................... 40

1.2.1.2 Inchworm locomotion mechanism ........................................................................................ 43

1.2.1.3 Autonomous capsules............................................................................................................ 48

1.2.2 Steerable distal end.................................................................................................................... 49

1.2.3 Conclusions ............................................................................................................................... 53

1.3 Conclusions and our solution ............................................................................................................ 54


1.1 Introduction to colonoscopy

Colorectal cancer is a major public health problem in many countries. Colorectal cancer

(which includes cancer of the colon, rectum, anus, and appendix) is the second leading deadly

cancer among men and women combined, second only to lung cancer in the United States. In 2005,

104,950 new cases of colorectal cancer will be diagnosed and 56,290 will die of this disease. Other

developed countries, such as France, the United Kingdom, have the same level of incidence. In

China, colon cancer incidence rates have been rapidly increasing in big cities in recent years. The

risk of developing colon cancer is increased for people more than 50 years old, and for those who

have previous incidents of colonic cancer within their family.

However, the great majority of these cancers and deaths could be prevented by applying

existing knowledge about cancer prevention and by wider use of established screening tests.

Screening can prevent many cases of colorectal cancer because most colorectal cancers develop

from adenomatous polyps. Polyps are noncancerous growths in the colon and rectum. Detecting

polyps through screening and removing them can actually prevent cancer from occurring.

Furthermore, being screened at the recommended frequency improves the chance that colorectal

cancers will be detected at an earlier stage [AME2005], when:

• The cancer is more likely to be cured by surgery alone.

• The surgery needed is less extensive, and the recovery from surgery much faster.

1.1.1 Colon Cancer

Colorectal cancer is a cancer that develops in the colon or the rectum. The colon and rectum are

parts of the digestive system, which is also called the gastrointestinal, or GI, system. The digestive system

processes food for energy and rids the body of solid waste.

After food is chewed and swallowed, it travels through the esophagus to the stomach. There it is

partially broken down and sent to the small intestine where digestion continues and most of the nutrients

are absorbed. The small intestine is actually the longest part of the digestive system- about 6 meters long.

Cancer almost never arises in the small intestine.

The small intestine joins the large intestine in the lower right abdomen. The first and longest part

of the large intestine is the colon, a muscular tube about 1.5 meters long with an average diameter of

50mm. Water and mineral nutrients are absorbed from the food matter in the colon. Waste left from this


process passes into the rectum, the final 15 centimeters of the large intestine, and is then expelled (Figure

1.1).

The colon has 4 sections:

• The first section is called the ascending colon. It begins where the small intestine attaches to the

colon and extends upwards on the right side of a person’s abdomen.

• The second section is called the transverse colon since it crosses the body from the right to the

left side.

• The third section, the descending colon, continues downward on the left side.

• The fourth section is known as the sigmoid colon because of its S-shape. The sigmoid colon

joins the rectum, which in turn joins the anus.

Figure 1.1 Anatomy of the lower digestive system, showing the colon and other organs [NCI ]

Colorectal cancer usually develops slowly over a period of many years. Before a true cancer

develops, it usually begins as a noncancerous polyp which may eventually change into cancer. A polyp is

a growth of tissue that develops on the lining of the colon or rectum. Certain kinds of polyps, called

adenomatous polyps or adenomas, are most likely to become cancers. Once cancer forms in the large

intestine, it eventually can begin to grow through the lining and into the wall of the colon or rectum. The

extent to which a colorectal cancer has spread is described as its stage. Colorectal stages can be classified

as the following according to the seriousness of cancer:


• Local: Cancers that have grown into the wall of the colon and rectum, but have not extended

through the wall into invade nearby tissues.

• Regional: Cancers that have spread through the wall of the colon or rectum and have invaded

nearby tissue, or that have spread to nearby lymph nodes.

• Distant: Cancers that have spread to other parts of the body, such as the liver and lungs.

1.1.2 Colorectal cancer screening

However, the great majority of these cancers and deaths could be prevented by applying

existing knowledge about cancer prevention and by wider use of established screening tests.

Screening can prevent many cases of colorectal cancer because most colorectal cancers develop

from adenomatous polyps. Polyps are noncancerous growths in the colon and rectum. Detecting

polyps through screening and removing them can reduce mortality both by decreasing incidence

and by detecting a higher proportion of cancers at early, more treatable stages [SMITH 01,

PIGNONE 02]. Therefore the American Cancer Society and the US Preventive Services Task Force

recommend that clinicians routinely provide colorectal cancer screening to all men and women

aged 50 and older. Persons at higher risk, for example those who have previous incidents of colonic

cancer within their family, should begin screening at a younger age and may need to be tested more

frequently.

Furthermore, being screened at the recommended frequency improves the chance that

colorectal cancers will be detected at an earlier stage [American Cancer Society 2005], when:

• The cancer is more likely to be cured by surgery alone

• The surgery needed is less extensive, and the recovery from surgery much faster.

Several options for colorectal cancer screening are recommended by the American Cancer

Society and other organizations to detect and diagnose colon cancer. These are summarized in

Table 1.1 [AME 2005] and described below.

• Physical exam and history: An exam of the body to check general signs of health, including

checking for signs of disease, such as lumps or anything else that seems unusual. A history of the

patient’s health habits and past illnesses and treatments will also be taken.

• Fecal occult blood test (FOBT): A test to check stool for blood that can only be seen with a

microscope. Small samples of stool are placed on special cards and returned to the doctor or

laboratory for testing.


• Digital rectal exam: An exam of the rectum. The doctor or nurse inserts a lubricated, gloved

finger into the rectum to feel for lumps or abnormal areas.

• Barium enema: A series of x-rays of the lower gastrointestinal tract. A liquid that contains barium

(a silver-white metallic compound) is put into the rectum. The barium coats the lower

gastrointestinal tract and x-rays are taken, shown in figure 1.2. This procedure is also called a

lower GI series.

Figure 1.2 Barium enema procedure. The patient lies on an x-ray table. Barium liquid is put into the rectum and

flows through the colon [NCI].

• Sigmoidoscopy: A procedure to look inside the rectum and sigmoid (lower) colon for polyps,

abnormal areas, or cancer. A sigmoidoscope (a thin, lighted tube) is inserted through the rectum

into the sigmoid colon. Polyps or tissue samples may be taken for biopsy.

• Colonoscopy: A procedure to look inside the rectum and colon for polyps, abnormal areas, or

cancer. A colonoscope (a thin, lighted tube) is inserted through the rectum into the colon, shown

in figure 1.3. Polyps or tissue samples may be taken for biopsy.

• Biopsy: the removal of cells or tissues so they can be viewed under a microscope to check for

signs of cancer.

• Virtual colonoscopy: A procedure that uses a series of x-rays called computed tomography to

make a series of pictures of the colon. A computer puts the pictures together to create detailed


images that may show polyps and anything else that seems unusual on the inside surface of the

colon. This test is also called colonography or CT colonography.

Figure 1.3 Colonoscopy. A thin, lighted tube is inserted through the anus and rectum and into the colon to look

for abnormal areas [NCI].

Table 1.1 summarizes the advantages and disadvantages of some main test & diagnostics methods

from several aspects, such as performance, accuracy, complexity and cost. The sigmoidoscopy and digital

rectal exam method only performs the testing of the colon. Other diagnostics methods, such as fecal occult

blood test, barium enema and are effective methods with lowest complexity, but colonoscopy will be

needed if there are some abnormalities. Virtual colonoscopy seems to be an efficient procedure that takes

less time and causes less pain. However, the doctor cannot take tissue samples during VC, so a

conventional colonoscopy must be performed if abnormalities are found. Also, polyps smaller than 10

millimeters in diameter, may not show up on the images.

On the other hand, colonoscopy can detect colon disease of the entire colon, including the large

intestine which other solution are not available, with the highest accuracy. Also, colonoscopy is the only

method that can operate within the colon so that surgeons can undertake treatment of colon. However, the

procedure of colonoscopy is the most complex of all the solutions and the patient needs to take a day off

for the examination. It should be emphasized that, even if it is rare, colonoscopy can cause intestine

perforation, as well as pain and anxiety for the patient. We will describe colonoscopy in details later

because it can provide a systematic therapy as well as a method of examination with the highest

performance results.

Gang CHEN

Thèse

INS

A d

e Ly

on, LA

I 2005

32

Table 1.1 Com

parison with different test procedures [A

ME 2005]

Cost range

Lowest cost: less than $20

Low to mid cost:$150-$200

mid to high cost: $300-$400

High cost: $400 or more.

Characteristics/ limitations

• Will miss most polyps and some cancers • May produce false-positive test results • Requires dietary limitations before testing • Must be done every year • For greater effectiveness, should be

combined with a flexible sigmoidoscopy every 5 years

• Additional procedures necessary if abnormalities are detected

• Visualize clearly only about one-third of the colon

• Cannot remove polyps • Can miss some small polyps and cancers • Very small risk of bowel tears or bleeding • More effective when combined with

annual fecal occult blood testing • Additional procedures needed if

abnormalities are detected

• Can miss some small polyps and cancers • Full bowel preparation needed • May produce false-positive test results • Additional procedures necessary if

abnormalities are detected

• Can miss small polyps and cancers, although more accurate than flexible sigmoidoscopy. Full bowel preparation needed

• Can be expensive • Usually requires some sedation • Generally requires missing a day of work • Carries potential risk of bowel tears or

infections.

Accuracy in

detecting cancer

and complexity

Intermediate for cancer Lowest complexity

High for up to one-third of the colon

Intermediate complexity

High High complexity

Highest Highest complexity

Performance & advantages

• No bowel preparation • Sampling is done at home • Low cost • Proven effective in

clinical trial • No risk of bowel tears or

infections

• Faily quick, few complications

• Minimal bowel preparation

• Done every 5 years • Minimal discomfort • Does not require a

specialist

• Can usually view entire colon

• Few complications • Done every 5 years No sedation needed

• Can usually view entire colon

• Allows biopsy and removal of polyps

• Done every 10 years Can diagnose other diseases

Test method

Fecal occult Blood test

Flexible sigmoidoscopy

Double-contrast barium enema

Colonoscopy


1.1.3 Colonoscopy

As described before, colonoscopy allows the physician to look inside entire large intestine, from

the lowest part, the rectum, all the way up through the colon to the lower end of the small intestine. Figure

1.4 shows the anatomy of the digestive system. The procedure is used to look for early signs of cancer in

the colon and rectum. The main instrument that is used to look inside the colon is the colonoscope, which

is a long, thin, flexible tube with a CCD video camera and a light on the end. By adjusting the various

controls on the colonoscope, the physician can carefully guide the instrument in any direction to look at

the inside of the colon. A high quality image from the colonoscope that gives a clear, detailed view is

shown on a TV monitor. This procedure also allows other instruments to be passed through the

colonoscope for the purpose of minimally invasive surgery (MIS). They may be used, for example, to

painlessly remove a suspicious-looking growth or to take a biopsy-a small piece for further analysis. In

this way, colonoscopy may help to avoid surgery or to better define what type of surgery may need to be

done.

Figure 1.4 The anatomy of the digestive system [JACKSON ]



1.1.4 Colonoscope

A flexible colonoscope is a special kind of endoscope which is used to detect colon cancer.

Now, these colonoscopes come in two types. The original purely fiberoptic instrument has a flexible

bundle of glass fibers that collects the lighted image at one end and transfers the image to the eye

piece (figure 1.5).

Figure 1.5 Fiberoscope photo with the intervention tool

The colonoscope also includes extra channels for infusing or withdrawing liquid or gas and for

passing instruments for electrosurgery, cautery, and for cutting and grasping. The use of such devices

has enabled viewing and treatment within the colon to be achieved without major surgery in some

cases. Figure 1.6 shows these accessories for colonoscope.

Figure 1.6 The accessory tools for an effective operation: the left is the video and the right is connection to

lighting source



In the last thirty years, new technologies of imagery have encouraged the evolution of the

endoscope and its performances. It is necessary, however, to note that endoscopic tools did not carry

out honest evolutions from a mechanical point of view. Indeed, the guiding principle of the

movements of this tool has always remained the same one.

Although current colonoscopy systems are well designed, carefully manufactured, use state of

the art instruments, and represent the result of a continuous product evolution, they are conceptually

still the same devices introduced about 30 years ago with the same movement principle.

The mobility of the fibroscope is implemented by a cable-driven system which is actuated by two

knobs (figure 1.7a), which make it possible for the distal end to perform movements in two orthogonal

directions (figure 1.7b). The combination of these movements makes the instrument bend in all the

directions (360°) in a 3-D space. Most of the current colonoscopes have the capability to bend 160°.

(a.) (b)

Figure 1.7 The control of the colonoscope and its bending

The newer video endoscopes use a tiny, optically sensitive computer chip at the end.

Electronic signals are then transmitted up the scope to a computer which displays the image on a large

video screen.

Since Olympus is the provider of the colonoscopy system for the Hospital Edouard Herriot de

Lyon, our medical partner of the project, we will present the terminology and the characteristics of

OLYMPUS colonoscope in Figure.1.8. There are four main parts: the connector, the universal cord,

the handle and the introduction sheath.



Figure 1.8 Terminology and the characteristics of OLYMPUS colonoscope



1.1.5 The colonoscopy examination

Before the examination, the colon must be completely empty for the colonoscopy to be

thorough and safe. For the procedure, pain medication and a mild sedative are given to the patient for

comfort and relaxation during the exam. The physician will insert a colonoscope into the rectum and

slowly guide it into the entire colon. By using the image transmitted from the camera at the distal end,

the physician can carefully examine the lining of the colon, figure 1.8a shows the video of the colon.

This is done by rotating the knobs to make the scope bend, so that the physician can move it around

the curves of the colon. The scope also blow air into the colon, which inflates the colon and helps the

physician see better.

If anything abnormal is seen in the colon, like a polyp or inflamed tissue, the physician can

remove all or part of it using tiny instruments passed through the scope (figure. 1.8b). That biopsy is

then used for further analysis. If there is bleeding in the colon, the physician can pass a laser, heater

probe, or electrical probe, or can inject special medicine through the scope and use it to stop the

bleeding.

It should be emphasized that, although they are uncommon, bleeding and puncture of the

colon are possible complications of colonoscopy.

Colonoscopy takes 30 to 60 minutes. The sedative and pain medicine should keep the patient

from feeling much discomfort during the exam. Following the procedure, the patient will need to

remain at the colonoscopy facility for 1 to 2 hours until the sedative wears off.

(a) (b)

Figure 1.9 (a) is the photo of the colon from the examination; (b) the biopsy operation [JACKSON]



1.1.6 Drawbacks of conventional colonoscopy

In the late 1960s, the colonoscope was first used for diagnosis and treatment of colon cancer

without the need for open surgery. Although it was developed nearly 40 years ago, colonoscopy is still

a skill which requires motivation, determination and dexterity. It has benefited humans in many

aspects a few decades ago. However, there is still room for further improvement. The drawbacks can

be classified as two aspects: the complexity of the procedure and the pain and discomfort of the

patient.

1.1.6.1 Complexity of the procedure for the surgeon

In order to perform a colonoscopy, the physician needs to insert a flexible tube about 1.6

meters in length into the patient for the purpose of observation, analysis and diagnosis. The

colonoscope is advanced by a variety of “in-and-out” maneuvers of the physician’s hands,

accompanied with pulling, wriggling, jiggling, shaking and torquing action to “accordion” the colon

on the colonoscope. During this procedure, there is also another important movement- the steering of

the distal end around the many bends of the colon. It requires many years of practice and training.

During the operation, the lumen may disappear from the surgeon’s sight, leading to a “red-out” when

the tip is against the colonic wall, or worse a “white-out,” when the tip stretches the colon wall. When

this happens, an inexperienced endoscopist may be disorientated and have difficulty looking for the

lumen. Perforation of colon may occur.

Furthermore, abrupt movements of the scope may result in tearing of the inner wall of the

colon, which may in turn lead to excessive bleeding. The present colonoscope also requires the

physician to hold the control device with one hand leaving only one hand to push or pull the insertion

tube. Too much torquing of the insertion tube may result in loops, which may complicate matters

further (figure 1.10). However, this rarely occurs in reality. Besides being cumbersome, holding up the

control device for prolonged periods of time is tiring for the physician.

Figure 1.10 loops in the insertion tube in a X-ray.



Currently, the colonoscopy procedure depends very much on the skill of the surgeon. A more

experienced physician will perform a more thorough, less painful operation in a shorter amount of

time than an inexperienced physician.

A skilled physician will normally have few problems traversing the colonoscope right up to

the caecum of a “normal” colon. However, there will be difficulties traversing the colonoscope

through some “difficult ” colons. This happens when encountering very acute or fixed bends. Further

pushing of the colonoscope at this point will only distend the walls of the distal colon. Distortion of

the colon shape and profile due to previous surgery may add to this problem.

Polyp removal from the colon walls can also cause difficulties. If there are a few polyps

present, the surgeon will have to remove them one at a time. If the polyps are large, the colonoscope

may have to be reinserted to look for the next polyp. Small polyps may often be retrieved with a

polyps trap. A biopsy net may be used to collect polyps and reduce this problem. However, one cannot

then distinguish which location in the colon a particular polyp comes from. It is important for the

physician to know which part of the colon a particular polyps is removed from if subsequent therapy

becomes necessary after histological examination.

1.1.6.2 The pain and discomfort for the patient

During the procedure, the air is filled in to distend the colon for the facility of the introduction

of colonoscope to the colon. This action causes discomfort for the patient and other reasons for the

pain to the patient are perforation and bleeding. Although colonoscopy is a safe procedure, perforation

can sometimes occur. This is a puncture of the colon wall, which could require additional surgery.

Bleeding also happens when a biopsy is performed. Heavy bleeding may result and sometimes this

requires a blood transfusion or reinsertion of the colonoscope to control the bleeding. Furthermore, an

inexperienced physician may cause additional pain by using the wrong technique or too much

unnecessary force. Even an experienced physician many cause pain if the patient is anxious, suffering

from irritable bowel syndrome, or if the colon is fixed by adhesion or disease.

1.2 Overview of current efforts on the automation of colonoscopy

(state of the art of robotic colonoscopy)

As it is analyzed in previous section, colonoscopy is an important procedure for inspection and

treatment of colon cancer, which ranks second among cancer deaths in most of the developed

countries. However medical experts predict that the death toll due to colon cancer could drop by 50%

to 75% with mass screening of the population. Unfortunately, due to the pain and discomfort

experienced by the patient, flexible colonoscopy procedure is very unpopular. Physicians also

complain of the high technical requirements and difficulties involved in introducing long, flexible



shafts into the patient’s anus [COT 90]. These difficulties are explained in the complicated procedure

described before: the need to insert the traditional colonoscope into the colon which is long and soft

and the difficulty of maneuvering of the distal end without direct control. Thus great efforts have been

made on the automation of colonoscopy which was first proposed in the review [PHEE 97] (also can

be called robotic colonoscopy). By automating colonoscopy with the aid of robots, the problems

mentioned above may be solved efficiently because of the following advantages to this approach:

• Automation removes the need for experience and skills of the operator. This means that a

patient will have the same treatment, in terms of time taken and comfort, regardless of the

physician performing the examination.

• Training of a physician may be reduced to learning treatments for abnormalities found on the

intestinal walls, without the need to perfect the manual skills required to use a conventional

colonoscope.

• With an automated procedure, more operations can be done by one surgeon, since only

diagnostics will be required, thus reducing costs.

• Reduced trauma and discomfort for patients.

• Reduction of postoperative complications and hospitalization.

With the automation of colonoscopy, the skills of the surgeon will no longer be the dependent

factor. Instead, the integration of robot into the colonoscope will make the procedure faster, more

precise and consistent. The surgeon, however, must guide the machine to do its job. It is still the

person who will decide every move the computer makes and who will take over when there are

uncertainties or in case of an emergency.

So far, there are two different kinds of approaches that focus on the design of new medical

instruments for colonoscopy according to the minimally invasive surgery (MIS). The first class aims

to increase the dexterity of the traditional colonoscopy by adding active [IKUTA 88] or passive

[STURGES 91] degrees of freedom to the distal end of the structure. This approach emphasizes the

creation of the new bendable tip to facilitate the insertion through the intestinal bends while the

introduction action is still kept for the physician. In this sense, the approach is called the semi-

autonomous colonoscopy. The other approach aims to drastically change the way the examination is

performed, which is also called autonomous colonoscopy. Instead of inserting the colonoscope into the

colon by the physician, the new design has the ability to propel itself into the whole colon. Although

they differ in their design mechanism, the two classes can be considered using two aspects of an

intervention: locomotion design and design of the steerable distal end, which are the two main actions

during a colon intervention. The following section will look at the related research into robotic

colonoscopy done by researchers in terms of these two aspects.



1.2.1 Locomotion mechanism

For the automated colonoscope, the most important concern is to design a robot that can

propel itself through the whole colon without hurting the colon wall. The human colon is a long

channel of varying shape and diameter, whose walls can be silky smooth at one section or thrown into

turbulent folds in another, yet at some points can be dry and rough. To make matters worse, the layout

of the colon consists of unpredictable flexible 3-D curves and bends, which are nearly impossible to

describe mathematically. To design a robot that can accommodate such variations and propel itself

through the entire organ poses great challenges. [PHEE 97] summarized the following criteria when

building a robotic colonoscope.

• The body of the robot must be flexible enough to conform to the acute bends found in the colon.

Any rigid distances must be kept to a minimum. Generally, the robot’s body surface (excluding

the propulsion mechanism ) must be smooth and well lubricated to reduce friction as it slides

against the colon walls.

• The rigid diameter of the robot should not be greater than 29 mm, which is the smallest average

internal diameter of the colon.

• The robot must be capable of compelling itself right up to the caecum for a thorough colonoscopy

examination.

• The propulsion mechanism is preferably arranged at the distal end of the robot, so that its path will

not be restricted by the curves and bends found in the colon.

• Any mechanism used to grip onto the colon walls must be blunt and preferably made of a soft

materiel. Hard objects with sharp edges will easily damage the delicate colon walls.

• The robotic colonoscope must have cavities running through its length to allow optical fibers,

air/water tubing, and surgical tools to pass through to its distal end.

The animal kingdom has provided inspiration in the study of various locomotion techniques. In the

field of robotic colonoscopy, much of the development simulates the way an animal moves: snake,

inchworm and others.

1.2.1.1 Snake-like locomotion

Most snake species move by using their ventral scales, the scales on the undersides of their

bodies, to pull themselves across rough surfaces. They use a serpentine locomotion movement, in

which the body assumes a position of a series of S-shaped horizontal loops and each loop pushes



against any surface resistance. [IKUTA 88], pioneers in this field, developed an “active endoscope”

that uses Shape Memory Alloy (SMA) in 1988. They made use of the resistance of the SMA in a

feedback control scheme to guide the snake-like robot around obstacles. The SMA tendons were

arranged about a spine so that each section can bend in three dimensions, as shown in Figure 1.11(a).

(a) (b)

Figure 1.11(a) the inner structure of an active endoscope (b) sequence motion in the sponge rubber colon

[IKUTA 88]

The SMA springs were connected mechanically in parallel, but electrically in series. This arrangement

increased the absolute value of electric resistance of the SMA, without any reduction of its

performance. This also eliminated the need for sensors such as potentiometers and encoders. The

driving mechanism of each segment consists of a stainless-steel coil spring, which acts as the main

skeleton at the center of a joint, and a series of SMA coil springs arranged around the joint. In this

model, each segment has one degree of freedom, so that a pair of SMA actuators, which are capable of

antagonistic motion, are arranged in symmetry with respect to the axis. It is this antagonistic activation

of the SMA springs that brings about the required bending motion. The basic design of the active

endoscope model was done by considering its application to a fibersigmoidscope. For this purpose, the

endoscope has enough mechanical compliance to pass through the sigmoid colon. It has a 13mm

diameter, which is comparable with endoscopes in the market of 10 to 20mm. This model has five

sections, comprised of four sections with flexibility in the same direction on a plane and one section of

the tip which can bend orthogonally to this plane just like traditional endocsope. The snake was

operated manually via a joy stick. Figure 1.11b shows the test results in a colon model environment.

The snake robot proved to have a maximum bending angle of 60° at the responding speed high enough

for the purpose.

[STURGE 91 ] proposed an idea of a spine in a floppy state that could slide through an

endoscope and then made rigid so that the endoscope itself can slide over the spine which guides it

around bends and prevents looping. A flexible, tendon-controlled bead-chain device was designed that



incorporates the “slide motion” scheme to traverse into the colon. The robot consists of two major

parts: one or two “spines” and an endoscope conduit, which is a covering tube for the spine, Figure

1.12.

Figure 1.12 cross-section of endoscope with controllable stiffness spine [STURGES 91]

The spine was made up of a series of a close fitting balls and sockets arrangement, as shown in

figure 1.13a. Initially, the fittings are free to rotate but as the cable that runs along the axis of the spine

is tightened, friction is developed between the fittings and ultimately there is an increase in the

apparent stiffness of the entire chain. To summarize, pulling the cable stiffens the bead chain and

relaxing the cable tension force loosens it. Figure 1.13b shows a stiffened bead chain.

(a) (b)

Figure 1.13(a) Alternating bead-shape sequential chain figure;(b) Bead chain [STURGE 91]

1.2.1.2 Inchworm locomotion mechanism

An inchworm moves by alternately extending and distending sections of its body to produce

peristaltic waves that drive it through the soil. This type of locomotion is particularly suited to

unstructured or even hostile environments where wheels and tracks fail [HIROSE 93]. An inchworm

device would function especially well in a tubular, 3-D terrain. Realizing its potential, various

researchers have developed pipe inspection devices [ANTHIERENS 99, FUKUDA 89 ] based on this

inchworm-type locomotion. In the endoscope field, [FRAZER 79] first adopted the self-propelled



mechanism to robotic colonoscopy. He filled a patent in 1979 illustrating the robotic sequence. An

endoscope is disclosed having a propulsion mechanism and at least one transmitter at the distal end

transmitting bursts of energy waves (radio frequency or ultrasonic) used for tracking the position of

the distal end through the use of two or more transducers on the anterior or lateral surfaces of a patient.

The propulsion mechanism may consist of two radically expandable bladders separated by an axially

expandable bellows with only the forward bladder attached to the distal end so that by expanding and

contracting them in proper sequence, propulsion of the endoscope is achieved. The most critical factor

was to assure adequate friction to anchor the inflated bladder onto the colon walls so that it becomes

the base for the subsequent bellow’s expansion and deflation.

Figure 1.14 inchworm-based robotic endoscope [SLATKIN 95]

[SLATKIN 95, BURDICK 94] used the similar locomotion technique and developed an

inchworm robotic endoscope that can have many similar sections, as shown in figure 1.14. One

prototype is composed of 3 grippers and 2 extensor actuators with a diameter 22.2 mm and the length

of 183-200 mm at the contacted and stretched state. The grippers are toroidal, inflatable balloons that

are attached onto the outside of each segment. The primary purpose of the grippers is to provide

traction against the wall by expanding radically outward. Extensors are made of rubber bellows which

connect the grippers at its two ends. They extend or retract like pneumatic cylinders when high or low

pressure air is introduced, respectively. For the locomotion control, each actuator, extensor, or gripper

is controlled by its own miniature solenoid valve located within the robot itself. A control bus extends

through the robot, linking all the solenoid valves. This bus is connected to a controller and a

receiver/transmitter that controls the movement of the robot as a whole. Some things to note for this

design are that the bracing action must be strong enough to prevent slipping of the robot for the

operation in the colon. Another noteworthy aspect is that the sequence involved in the inchworm mode

of locomotion can be extensively varied depending on the gripper/extensor configuration. This robotic

endoscope prototype has been tested in the intestine of a pig. The reported experimental results in vivo

were positive, but the authors pointed out that the adhesion was not adequate to provide satisfactory



traction. Furthermore, since the work environment of endoscope is soft and slippery, the locomotion

efficiency can be a vital problem for the colonoscopy.

Figure 1.15 Automated colonoscope designed by [WALTER 95]

[WALTER 95], research at the Rochester Institute of Technology, also developed an

automated colonoscope. Similar to Burdick’s robotic endoscope, balloons are used in their design to

grip onto the colon walls. To lengthen and shorten the colonoscope, a push-pull flexible rod is used.

The back-end balloon is connected to the outer sheath of the flexible rod, whereas the front-end

balloon is connected to the inner core of the flexible rod. A pneumatic cylinder is used to drive the

core in and out of the outer sheath. By employing the inchworm method, the robot can be propelled

into the colon, as illustrated in Figure. 1.15.

Since the activation of the extension mechanism is from the proximal end and outside the

patient’s body, extension and retraction motions are more positive and more robust than most of the

earlier mentioned designs. However, due to the presence of relative motion of the push-pull rod with

respect to the colon walls, friction may be of concern. Friction force depends on the area of contact

between the flexible rod and the colon walls. It is also dependent on the degree of curvature through

which the rod is made to bend. Furthermore, buckling may occur at the distal end of the push-pull rod

if the stroke, pushing the front-end balloon forward, is too long.

Instead of using an inflated balloon as the clamping mechanism on the colon walls,

[CARROZZA 96, CARROZZA 97, DARIO 97, 99] utilize another clamping method which uses

suction as the base of generating friction. As reflected in figure 1.16, suction is provided by a number

of small holes disposed along the actuator’s surface. The prototype clamping actuator comprises four

series of eight holes with diameter of 1mm. When a vacuum is introduced, the negative pressure at the



small holes will cause the clamping actuator to ‘suck’ onto the colon wall thus attaching the micro-

robot. The central module is used for extension. By a sequence of activating the extension and

clamping mechanism, the micro-robot can traverse up the colon using the inchworm method of

locomotion, shown in Figure 1.17.

Figure 1.16 Inchworm robot designed by [DARIO 97 ]

Figure 1.17 sequence of inchworm propulsion steps of the microrobot [CARROZZA 96]

Suction does generate traction onto the colon however undesirable lesions may appear when

the vacuum pressure is increased beyond a certain value. [MENCIASSI 01] improves the gripping

efficiency by introducing a new clamping mechanism which integrates suction and mechanical

clamper. As shown in the figure the clamping mechanism is placed into the colon with its jaws

opened. The vacuum is introduced thus causing the surrounding tissue to collapse into the open jaw.

After which the jaw closes therefore clamping the tissue and hence achieving a positive grasp. A

prototype, as shown in figure.1.18, was developed and a vivo experiment on a pig was conducted. It

was recorded that the robot transversed a distance of 55cm from the anus after which the device was

observed to remain stationary. It demonstrated high stretch length and clamping efficiencies however

the low retraction efficiency affects the overall locomotion performance.

Figure 1.18 robot developed by [MENCIASSI 01]



On the basis of this model, [KIM 02, 03] in collaboration with IMC, Seoul, Korea, developed an

improved version of the semi-autonomous colonoscope with shape memory alloy steerable and

telescopic tip, complementary metal-oxide-semiconductor (CMOS) camera, light-emitting diode

(LED) illumination system, and very long stroke (about 12cm) (figure 1.19 ). During several in vivo

tests on pigs, this prototype showed the same performance as traditional colonoscope in terms of

distance traveled.

Figure 1.19 Integrated robot for colonoscopy [KIM 02]

[ASARI 00, KUMAR00] proposed a design which was comprised of an extensor module

sandwiched between two clamper modules, as shown in Figure 1.20. A new concept of clamping the

colon wall based on the passive vacuum devices is forwarded in Figure 1.21. Each clamper module is

a closed toroidal balloon with six passive vacuum cups embedded onto its interface to give it a better

grip. The extensor module was designed with three parallel pneumatic bellows which allows both

axial extension as well as bending of the robot’s tip. When the pressure in the three bellows is equal,

the extensor module works as an extensor. Otherwise, it works as a bending tip. When pressured air is

introduced into the clamper module, it inflates thus stretching the colon. When the resultant force

created at the area of contact further restrains enlargement of the clamper, the vacuum cups will be

pushed thus flattening it. In doing so, the air beneath the cups escapes, therefore creating a vacuum,

which in turn generates a positive adhesion. The extensor module will then be activated to either

axially extend or bend or both depending on the requirements.

Figure 1.20 Inchworm robot designed [KUMAR00]



Figure 1.21 The clamping mechanism of the micro-robot [KUMAR00]

In addition, a path-planning scheme integrating image and tactile sensor information for active

guidance and navigation of the micro-robot in the human colon have been proposed for the purpose of

observation, analysis and diagnosis. The proposed colonoscopy system was tested with physical

models and animal colons. The results of the tests were encouraging, but the author met the same

problems as the other researchers. Since the colon diameter changed at different sections, it made the

clamping to the wall difficult. Therefore, in the locomotion of the proposed device, the efficient

clamping of the colon wall still remains a challenge.

There are also other locomotion techniques inspired by other animal movements, such as

lizards and ants and octopi. Also, other methods some which are mechanical are studied for

locomotion purposes used during a robotic colonoscopy which can be found in Kassim’s survey

[KASSIM 03].

1.2.1.3 Autonomous capsules

In addition to the locomotion mechanism inspired by the animal movement as described

earlier, the idea of using natural peristalsis has been proposed and autonomous capsules have been

made to perform diagnosis and even therapy of the gastrointestinal tract. With the camera, light

source, transmitter and power supply integrated into a capsule, the patient can swallow and repel it

through natural peristalsis. In this case a pain free endoscopy is possible.

In 1997, [IDDAN 97] patented an idea describing a swallowable capsule, which includes a

miniature camera system, light source and power supply inside a capsule with a transparent front

portion. The capsule is mainly intended to inspect the small intestine. However in 2000, [GONG 00]

developed a capsulated wireless endoscope prototype, which incorporates a miniature charge-coupled

device camera and processor, a microwave transmitter and a halogen light source powered by small



batteries, as shown in Figure 1.22. High quality color television images have been transmitted using

this wireless endoscope in anaesthetized pigs.

Figure 1.22 Endoscopic capsule from Given Imaging [GIVEN]

An Israeli company Given Imaging [GIVEN] developed the first commercial disposable

capsulated pill named M2A which incorporates a light source, a miniature color video camera battery,

antenna and a radio transmitter figure. Images captured by the camera are transmitted by radio

frequency to an array of sensors worn around the patient’s waist where the signals are recorded

digitally. To use M2A, the patient simply needs to swallow the pill, put the sensor around their waist

and proceed with their daily affairs. After approximately eight hours or after detecting that the capsule

has been excreted, the patient removes the sensor and returns it to the clinic where the images are

downloaded and the doctor examines the video to look for abnormalities. The entire process is painless

and convenient for both the patient and the doctor. A step ahead in this direction has been performed

with another autonomous capsule: the NORIKA3 (RFSystem Lab, Japan), which is able to propel

through the gastrointestinal tract by exploiting the force generated by external electromagnetic fields

which can be tuned by a joystick [NORIKA3 Online]. The capsule incorporates a CCD camera and

some drug-delivery modules for localized therapy. This system doesn’t incorporate on-board

intelligence and is essentially a wireless teleoperated device rather than a reactive and adaptive

system.

1.2.2 Steerable distal end

Traversing a colonoscope from the rectum to the caecum of the colon is only part of the

journey toward automation of colonoscopy. It is important for the distal end of the automated

colonoscope to be able to bend or be steered towards a desired direction. During a traditional

colonoscopy, the medical doctors use the colonoscopic images not only to perform the diagnosis but

also to assist the introduction of the device into the colon and to control its advancement. On the basis

of the endoscopic images, doctors look for the colon lumen position and orient the steerable tip of the

colonoscope in order to follow the right direction. The tip is generally cable actuated and doctors can

drive it by using a knob on the colonoscope handle.



In order to replicate the traditional colonoscopic procedure, the design of autonomous

steerable distal tip is another important concern for the automation of colonoscopy.

[FUKUDA 94] proposed a shape memory alloy (SMA)-based bending devices with 2 degrees

of freedom which is called as microactive catheter (MAC). The basic structure of the MAC is shown

in Figure 1.23. The MAC is basically made of strips of SMA wires embedded at 120° intervals in a

cylindrical housing made of elastic material. When an electric current is introduced into one of the

SMA wires, it will be heated. In doing so, it will shorten in length, causing the entire MAC to bend

away from its central axis, as shown in figure 1.24. The angle of bend depends on the current carried

by the SMA wires. Thus, by individually controlling the flow of electricity into the three SMA wires,

the MAC can be made to bend in any desired direction at a specific angle. In order to increase the

bending angle, several MACs can be connected serially, and experiments have shown that a bending

angle can attain 80° with three MACs in series.

Figure 1.23 Bending principle of MAC [FUKUDA 94]

By using the same bending principle, [BAILLY 04a] developed a new active catheter for

endovascular aortic aneurysm treatment. The basic element of this catheter is constituted of three

metal bellows disposed 120° apart, providing three degrees of freedom. The bending angle of this

robot is obtained by individually controlling the water pressure in the chamber. With the connection of

several elements in cascade, the prototype of this catheter can obtain the bending angle of more than

90°.

In [MENCIASSI 02], silicone bellows are used to fabricate a bendable tip of the length of

30mm with the same bending mechanism as [FUKUDA 94]. It contains 3 small Shape Memory Alloy



(SMA) springs with a 120° layout. This configuration allows a 90° bending in three directions (Figure

1.24).

Figure 1.24 Steerable tip with LED illumination and CMOS camera [MENCIASSI 02]

As mentioned in the locomotion section, the extensor module of [ASARI 00, KUMAR00]’s

micro-robot for colonoscopy is comprised of three bellows. When the pressure in the three bellows is

equal, the extensor module works as an extensor. Otherwise, a bending angle can be obtained by

controlling the pressure individually.

Besides developing his robotic endoscope, [BURDICK 94] proposed in his patent an

alternative distal-end design. This design is a modification of one of his robotic endoscope segments

described earlier. The embodiment consists of four distinct inflatable sacs. These sacs, which are

comprised of an elastic material such as latex, are circumferentially located around a central core. This

core contains a high-pressure compressed line, a low-pressure or vacuum-gas return line, and a control

bus. Each sac is inflated or deflated by the action of valves. By controlling the relative pressure

distribution in the sacs, the segments can not only extend but also bend actively. However, the

growing incidence of Latex sensitivity in various populations will preclude the use of this material in

any device that comes in contact with a person.

[PEIRS 00, 01] designed a miniature manipulator for integration in a self-propelling

colonoscope. The propulsion unit is the same as the inch-worm robot designed in [DARIO 97]. The

manipulator is used to orient a camera and some tools and has two bending degrees of freedom

( ± 40°). It consists of two modules (figure. 1.25) driven by an electromagnetic motor with worm gear

reduction. Each module is 12.4mm in diameter and 20mm long.

Chapte

r 1 F

rom

the p

roble

m o

f colo

nosco

py to

the so

lutio

n o

f robotic co

lonosco

py

Gang CHEN

Thèse

INS

A d

e Ly

on, LA

I 2005

52

Figure 1.25 the structure and implem

entation of the miniature m

anipulator for colonoscopy [PEIRS 00]

Table 1.2 the summ

ary of various robotic colonoscopy system

Contact

with the

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Colonoscope specific features

Rapid and without human

intervention for the navigation

Quick reactivity, but limited

DOF

1 DOF, small size to integrate

other tools, weak bending

angle.

1 DOF, small size to integrate

other tools, weak rotation

angle. Can only take the lower GI

endoscopy

Self-propelled robot, very

flexible as a whole unit, but

3 DOF, small bending angle

3 DOF, small bending angle

and not flexible

Amplitude

55° in all

directions

15° / segment

(12 segments)

± 40° from one

rotation axe

From – 45° to

+60° from one

rotation axe

90° in all

directions

35° maximum

in 3 directions

50° maximum

in 3 directions

Movement

Bend and

stretch

Bend

Bend

Bend

Bend and

stretch

Bend and

stretch

Bend and

stretch

Bend and

stretch

Size

L : 50 mm

φ : 12 mm

L : 48 mm

φ : 15 mm

L : 40 mm

φ : 12.4

mm L : 21 mm

φ : 8.5 mm

φ : 13 mm

L : 30 mm

φ : 18 mm

L : 50 mm

φ : 15 mm

L : 25 mm

φ : 19 mm



Act

uato

r

Elec

trom

echa

nica

l

Elec

trom

echa

nica

l

Elec

trom

echa

nica

l

Elec

trom

echa

nica

l

SMA

SMA

Elec

trica

l

Pneu

mat

ic

( inc

hwor

m)

[BU

RD

ICK

94]

[PEI

RS

97]

[PEI

RS

00]

[PEI

RS

00]

[IK

UTA

88]

[MEN

C 0

2]

[PEI

RS

01]

[KU

MA

R 0

0]

1.2.3 Conclusions

We have introduced the state of the art of robotic solutions for automation colonoscopy:

locomotion and steering the distal end to the right direction of progression. Table 1.2 summarized the

characters of each robotic colonoscopy system. From the table, we can see that most of the robotic

colonoscopy systems used the inchworm-based locomotion mechanism [PEIRS 00 and 01, DARIO 99,

BURDICK 94 ]. But this movement needs to clamper the colon wall in order to get the advance power

in the colon. Since the colon is soft and flexible and it can move with the colonoscope, this problem is

a great challenge during a real colonoscopy. The first concern is the efficiency of advancement and the

other concern is the possible damage to the colon wall. A plausible solution for these problems is to

apply strong force so that the robot can clamper the colon firmly and can generate the reliable

advancement. However, such a solution will cause pain to the patient. Although [MENCIASSI 01,

KUMAR00] tried to improve the efficiency of clamping, the solution will need to be tested in more

experiments to know its reliability.

Another challenge for the conventional colonoscopy is the adjustment of the distal end to the

right direction for the progression. Also, many researchers [DARIO 99] [BURDICK94][PEIRS 00]

[KUMAR 00] have proposed several design schemes for the bending tip which are integrated into the

whole robotic colonoscopy system. [KUMAR 00] used a vision-based path-planning method to guide

the colonoscope. Thus the procedure can greatly reduce the possibility of contact with the colon wall.

Inspired by the problem of efficiency of navigation and some discussion with surgeons, we have

decided to focus our research on the design of a robotic manipulator which can automatically guide the

introduction of the colonoscope, and not on surgeons during the progression of the colonoscope. This

solution will completely avoid the disadvantage of the self-propelled robotic colonoscope and will

greatly reduce the workload of the surgeon.



1.3 Conclusions and our solution

This chapter touches the subject of this thesis from the problem of conventional colonoscopy

to its improvement by using a robotic solution. The first part deals with the problem of conventional

colonoscopy. The current situation of colon cancer in the world has been discussed, and then various

diagnostics and treatment methods are analyzed and compared. Following this, the conventional

colonoscopy has been described in detail as well as the instruments and the examination procedure.

After that, the drawbacks of the conventional colonoscopy have been presented from two aspects: the

complexity of the operation and the pain to the patient.

To facilitate the conventional colonoscopy procedure, a robotic colonoscopy solution has been

proposed in the second part. State of the art robotic colonoscopy systems have been summarized. For

the purpose of inspection and intervention in the colon, the robotic instruments have been studied from

two aspects:

• The autonomous locomotion aspect which makes the robot propel itself in the colon. Here, the

locomotion mode used most is the inch-worm movement which uses the clamper to cling to the

colon wall and then stretches itself by using the pneumatic bellows.

• The bending distal end of colonoscope is in full evolution. Shape Memory Alloy (SMA) actuator,

hydraulic actuators and electromechanical actuators are often presented to improve the bending

performance. The aim is, through adjusting the bending direction, to guide the progression of the

colonoscopy in the colon.

In this thesis, our goal, as described previously, is to design a new bending robotic

manipulator to direct the progression with minimal contact between the instrument and the colon wall.

The following chapters will focus on the state of the art continuum robot, which is a kind of robot

suitable for our application, and our design of a new automatic bending robotic manipulator which will

replace the conventional cable-based distal end by the surgeon.

Chapter 2 Design and Construction of a Micro-robotic Manipulator for Colonoscopy


Chapter 2

Design and Construction of a Micro-robotic

Manipulator for Colonoscopy



2

CHAPTER 2 ........................................................................................................................................................ 55

DESIGN AND CONSTRUCTION OF A MICRO-ROBOTIC MANIPULATOR FOR COLONOSCOPY.............................................................................................................................................................................. 55

2.1 General Introduction ......................................................................................................................... 57 2.2 Continuum robots............................................................................................................................... 59

2.2.1 Backbone-based extrinsic continuum robot .......................................................................................... 60 2.2.2 Fluid/pneumatic power driven intrinsic continuum robot ................................................................... 61 2.2.3 Hybrid continuum robot ......................................................................................................................... 65 2.2.4 The key advantage of continuum robot compared with discrete manipulator................................... 66

2.3 Design of EDORA II .......................................................................................................................... 68 2.3.1 Introduction ............................................................................................................................................. 68 2.3.2 Previous works on robotic colonoscopy in the project of the laboratory ............................................ 70 2.3.3 The problems and shortcomings of EDORA ......................................................................................... 73 2.3.4 Construction of EDORA II ..................................................................................................................... 74 2.3.5 Discussions and Conclusions................................................................................................................... 78

2.4 Control system for EDORA II ............................................................................................................ 79 2.5 Conclusion ......................................................................................................................................... 81



In the chapter 1, the specific problems and difficulties of conventional colonoscopy have been

presented from the clinical view, and then the corresponding efforts which aim to facilitate the

maneuver and lessen the pain to the patient by using robotic colonoscopy have been explained in

details. Based on this analysis and the surgeon’s suggestion, we have decided to construct a novel

automatic bendable robotic manipulator to guide the advancement of a colonoscopy. In this chapter,

we will focus on this design in terms of robotics technology. This specially designed robotic

manipulator belongs to a new classification of robot without rigid joints, also called Continuum Robot

by the Davies [DAVIES 99], which is different from the conventional rigid-link robot. The related

work on the continuum robot will then be discussed and the design of our flexible robotic manipulator

will be described in detail based on clinical and technical requirements.

Figure 2.1 The conventional rigid robot manipulator

2.1 General Introduction

Over the last several decades research in robotic manipulators has focused mainly on designs

that resemble the human arm, and can be best described as discrete manipulation [ROBOSON 99].

The design of discrete manipulators is based on a small number of actuatable joints that are serially

connected by discrete rigid links, see figure 2.1. Discrete manipulators have proven to be very useful

and effective for many different tasks, but they are not without their limitations. These robots most

often have five to seven degrees of freedom (DOF), thus in a spatial environment they will most often

need all of their degrees of freedom just to position the end-effector. This design is very efficient for



open environments, but as constraints are added to the environment it is possible that the manipulator

may not reach its desired end-effector position. This failure is due to the lack of degrees of freedom in

the robot to meet both the environmental constraint conditions and the desired end-effector position

requirements. The manipulation of the robot in the colon in this dissertation is such an example.

Another drawback of discrete manipulators is that they require some types of specialized devices for

the manipulation of an object. Most often manipulation is done by attaching a gripper around a

manipulator, and once in the proper position the gripper is used to manipulate the object. Once again

this design works well in many cases, but it is possible that in some situations a strategy where the

robot itself and not the end-effector performing the grasping, i.e. whole arm grasping, must be a better

solution.

Direct manipulators can gain enhanced maneuverability and flexibility through the addition of

more degrees of freedom. This situation can be related to the diversity of biological manipulators. As

noted earlier, discrete manipulators resemble the human arm in structure, but looking at other

biological manipulators it can be seen that this is not the only design. Animals such as snakes, octopi

and the elephant trunk can produce motions from their appendages or bodies that allow the effective

manipulation of objects even though they are very different in structure compared to the human arm.

Even among these appendages, i.e. trunks, tentacles, etc., the physical structure can vary, but all share

the trait of having a relatively large number of degrees of freedom.

Research into manipulators with a large number of degrees of freedom or a high degree of

maneuverability has spawned many different designs. [ROBOSON 99] developed three classifications

for these types of robots in his review. The first class called discrete describes the construction of

conventional robots. As the number of discrete joints increase the redundancy or maneuverability of

the manipulator also increases, and the robot moves into the second classification known as serpentine

robots. This classification most often includes robots that are described as hyper-redundant

manipulators [CHIRIKJIAN 92]. With the combination of very short rigid links with a large density of

joints, this structure creates highly mobile mechanisms which appear to produce smooth curves,

similar to a snake. The third classification of robots known as continuum robots do not contain discrete

joints and rigid links as in the previous two classifications. Instead the manipulator bends continuously

along its length via elastic deformation and produce motion through the generation of smooth curves,

similar to biological trunks and tentacles of the animal kingdom [KIER 85]. It should be clear that

there are fundamental differences in form between conventional discrete, serpentine, and continuum

robots, figure 2.2 shows their differences. In this dissertation, only continuum robots will be

considered.



Figure 2.2 robot motion of three classifications

2.2 Continuum robots

As given from the definition in [ROBOSON 99], continuum robots do not contain discrete

joints and rigid links. They have a completely different design from the conventional robots. And its

movements are more close to biological movements which occur in nature. So the diverse movements

of the animal kingdom offer researchers inspiration and excellent examples for the design and

application of the robotic manipulator [KIER 85]. Tongues, elephant trunks and tentacles demonstrate

an amazing variety of abilities by which animals dexterously interact with and manipulate their

environment. For instance, giraffes wrap their tongues around high tree branches to strip off leaves.

They can also use their tongue to more delicately pick off leaves while avoiding the many spiny thorns

found in acacia trees. Elephant trunks are amazing appendages that are strong enough to knock over

trees and yet agile enough to pick straw off the ground. Squids have ten arms, two of which are

tentacles. These tentacles are specialized arms used especially for quick-strike prey capture. The other

arms on the squid, which are similar to octopus arms, allow the creature to perform more general

prey/object manipulation and locomotion.

Thus many manipulators mimicking these movements have been implemented for various

applications [ROBOSON 99]. One important application is grasping and manipulation. Continuum

robots exhibit a useful range of properties which ensure their application as the fingers of robot end-

effectors [SUZUMORI 91, LANE 99]. Inherent structural compliance increases grasp stability and

minimizes contact damage, whilst the absence of moving parts eliminates problems of friction and

reduces the risk of environmental contamination. The devices may also be easily cleaned for

application involving hazardous materials, food or medical production. The simple structure enables

lightweight mechanisms with long reaches to be considered for operation within constrained

environments with restricted access, such as storage tanks or hazardous waste handling in nuclear

plant. Also long continuum mechanisms are suited for positioning tasks requiring relatively low



positional accuracy with small payloads, such as industrial inspection, cleaning and bulk transport.

This structure compliance can also be exploited when working within constrained, unstructured or

delicate environments, since devices will deflect rather than generate large contact forces during

collisions with their environments. A typical example is the colon inspection using robotic

colonoscopy [IKUTA 88, DARIO 97] described in chapter 1. Due to the vast number of design

possibilities, [ROBONSON 99] gave a broad classification as “intrinsic”, “extrinsic”, or “hybrid”,

according to the method and location of mechanical actuation. In this dissertation, this classification

will still be used to classify the form of continuum robots with great details.

2.2.1 Backbone-based extrinsic continuum robot

The most popular design uses some type of “backbone” structure that is actuated by sets of

cables. This kind of design can also be called a cable-driven continuum robot. [Anderson 67]

presented a robot named the Tensor Arm Manipulator. The robot was based upon a backbone

composed of 15 small links serially connected with 14 two-degree-of-freedom joints. Each joint was

actuated by 4 monofilament tendons which yielded a total of 56 tendons for all 14 joints, and three

additional tendons were used to actuate a gripper. Hirose presented several different designs in

[HIROSE 93]. The most complex robot was based on a design very much like Cieslak and Morecki’s

robot. Hirose’s robot was based on a large coil spring that provides both support and flexibility. The

robot was actuated in eight locations where each actuation was provided through wire cables.

[HANNAN 01] developed an Elephant’s Trunk Robot. It is composed of a total of 16 degrees of

freedom joints yielding a total of 32 degrees of freedom (DOF) for the backbone (figure 2.3). The

manipulator is divided into four main sections ranging in diameter from 10.16 cm down to 6.35cm for

the final section. The actuation of these sections is provided through the use of a hybrid cable and

spring servo system.

Figure 2.3 Elephant Trunk Robotic Manipulator [HANNAN 01]



This kind of design has seen its application in medical fields. [WENDLANDT 94] designed a

continuum platform which is used to manipulate endoscopic tools. This platform is actuated by three

tendons to meet the small scale requirements in endoscopy. Using a multi-backbone snake-like

mechanism, [SIMAAN 04] designed a Distal Dexterity Unit (DDU) which is used for laryngeal

surgery. The DDU differs from previous work in terms of application, size, downsize scalability,

actuation, and kinematic architecture. In total, the DDU is equipped with seven actuated joints and has

six independent DOF. The whole system has 34 controlled DOF allowing the manipulation of up to

three tools inside the throat.

2.2.2 Fluid/pneumatic power driven intrinsic continuum robot

Another possible robot design used fluid/pneumatic filled tubes for actuation. The basic design

for intrinsic fluid/pneumatic power driven continuum mechanisms combines both the actuator and the

supporting structure into a single unit. This produces a simple, compact, light weight mechanism

which contains no moving parts and yet can generate motion with up to three degrees of freedom,

allowing both the direction and magnitude of tip movement to be controlled. Operation relies on the

elastic deformation of parallel actuator chambers placed at equal intervals about a central longitudinal

axis. Internal pressures are controlled to generate extensions forces and the structure deforms

according to constraints provided by the end forms. It is essential for the operation that internal

pressures generate axial extension rather than radial expansion and several approaches have been

developed to ensure anisotropic elasticity. Devices with many degrees of freedom can be obtained by

placing several independent actuators in a series.

These actuators exhibit a passive elastic compliance to external forces in various directions

normal to their longitudinal axis. External forces cause compliant motion of the actuator until the force

balance within the structure is restored. The resulting increase in strain energy causes the actuator to

return to its undisturbed configuration on removal of the external force.

Figure 2.4 Flexible actuator designed by [SUZUMORI 92]



[SUZUMORI 92] presented a type of flexible micro-actuator that could be used to design

robotic manipulators. Their design was based on pressurizing three radially mounted chambers to

obtain actuation. These simple actuators could not only produce bending motions, but they could also

elongate. More complicated robotic devices could be constructed with different arrangements of the

actuators. [WILSON 93] presented a robot that was constructed out of simple one degree of freedom

actuators. The actuators were simple tubes that when pressurized could bend in one direction.

[DAVIES 91, LANE 99] described a much larger 744mm long pneumatic device using three parallel

thin walled polymeric bellows connected at each end by rigid plates, shown in figure 2.5. The

convoluted bellow walls ensured that longitudinal extension due to internal pressure was much larger

than the radial expansion. This approach also produced a pneumatic gripper which exploited its

intrinsic compliance to perform stable open loop manipulations on a range of objects. Compliant

finger motion both reduces the risk of damage to grasped objects or fixtures due to excessive contact

force, and increases grasp stability by absorbing external disturbances and positional errors which

might otherwise lead to grasp failure.

Figure 2.5 Sketch of the AMADEUS gripper [LANE 99]

[OHNO 00, 01] presented another robot design called the Slim Slime Robot (SSR). Each

module of SSR is pneumatically-driven with three degrees of freedom, and has pneumatic actuators,

valves, displacement sensors and a microprocessor inside. The module has three metal bellows that are

arranged equally around the circumference, with respect to the axis of the module, and sandwiched

between two disks. The on-off solenoid valves for air intake and exhaust are installed at each end of

the bellows, respectively. The module can realize motion in three degrees of freedom: stretch, pitch

and yaw by controlling the intake of each bellows. The robot featured the unique design of using



miniature values placed directly inside the robot. And the entire robot was composed of six individual

modules. At the base of the Slim Slime Robot [SSR], [AOKI 02] designed Slim Slime Robot 2 (SSR-

II) with Bridle Bellows units composed of a large caliber bellows and wire lock system. Bridle

Bellows, an example of “Bridle drive”, is able to change shape by controlling wire length and air

pressure and produce large power. SSR-II system has added a degree of freedom to stretch the body

segment. The active cord mechanism (the snake like robot) is capable of performing several tasks in

narrow spaces, such as moving under collapsed houses, and inspection of pipelines at plants. Again

this design also has an observed application in medical field. [BAILLY 04b] proposed and developed

a new micro-robot for aortic aneurysm treatment. The structure of this micro-robot consists of two

bases interconnected by three 120 degree positioned bellows. The pressure variation inside the bellows

leads to their length variation, which induces the bending of the device. The catheter is equipped with

several micro-robots inserted inside its external sheath. The intermediate floors between the two bases

are used to maintain structural rigidity and to prevent the bellow from buckling while providing a

better bending capability. The bending movements are achieved by using hydraulic pressure. The

hydraulic pressure in the system is controlled by six servovalves with six pressure-sensors at their

outputs. Six hydraulic actuators transform oil pressure at the output of the servovalves into bio-

compatible liquid pressure inside the bellows, required in a medical field. A local feedback control is

performed to ensure pressure regulation in the bellows.

As the research effort into intrinsic continuum devices increases new methods of actuation are

being proposed. [KALLIO 98 ] described the control of a micro-manipulator using a similar parallel

bellows construction. Three small nickel bellows support and control the orientation of a platform,

which in turn moves a micro-manipulator arm. An innovative system of piezohydraulic actuation

operates the bellows producing a system with sub-micrometer resolution in a workspace several

hundred micrometers across. The continuum approach was ideal for this application because the

bellows are able to both extend and bend, enabling a compact structure to be produced by removing

the need for spherical joints (Figure 2.6).



Figure 2.6 Piezoelectric driven Micro-manipulator from [KALLIO 98].

[IVANESCU 95] suggested using electrorheological fluids to control fluid filled devices.

These fluids change viscosity in the presence of DC electric fields, and hence the provision of suitable

electrodes would enable continuum devices to be stiffened once a desired configuration had been

reached.

[KORNBLUH 98] described the use of Electrostrictive Polymer Artificial Muscle (EPAM)

actuators in robotic applications and suggested the construction of a multi-sectioned redundant

continuum arm. EPAM actuators contract when a voltage is applied across a polymer dielectric and

may provide a lightweight compact actuator. Since force is produced by contraction additional

supporting elements are required to prevent collapse of the overall continuum structure. Obviously

fluid powered artificial muscles such as the McKibben muscle [HIROSE 93] could also be used to

construct similar devices.

Another important actuation method uses shape memory alloys (SMA). This actuation method

lends itself to the production of small actuators and applications where low efficiency and slow

response are unimportant. Some works on SMA-based is used in the continuum robot has been studied

for medical application. [CIESLAK 99] presented an elephant trunk type elastic manipulator. The

backbone support for their robot was based upon a large diameter coil spring. The robot was divided

up into three main sections, each of which was actuated by four wire cables. As described in chapter

one, the design like [IKUTA 88] [FUKUDA 89] [MAEDA 96] [ARAMAKI 95] [MINETA 01] [LIM

96] [DARIO 02] for robotic colonoscopy belongs to the SMA-based continuum robot and there exist

designs for other medical applications.



Figure 2.7 The KSI Tentacle Manipulator [IMMERGE 95]

2.2.3 Hybrid continuum robot

The essentially hybrid structure follows a similar approach to extrinsic tendon devices, except

that the passive springs are replaced by actively controlled bellows. [HEMAMI 84] proposed a

potential construction for a redundant hybrid manipulator with several two degrees of freedom

sections. More recently, the commercially available KSI tentacle manipulator has been developed

[IMMERGE 95], shown in figure 2.7. A central pneumatic bellows is operated in conjunction with

two sets of extrinsic tendon triads. One triad inserts halfway along the bellows structure and controls

the shape of the proximal half. The other inserts at the free end and controls the form of the distal

portion of the device. The internal bellows pressure opposes the operation of the tendons, ensuring that

they always remain under tension. By varying the tendon lengths and the bellows pressure both the

length and stiffness of the structure can be controlled.

Based on the previous work on Elephant’s Trunk Robot [HANNAN 01], [JONES 04]

designed a novel continuum robot manipulator. The design features two concentric flexible cylinders,

with a pneumatically actuated inner tube and with tendons fixed to an outer cylinder. The tendons

control the bending of the continuous structure. Variation of pneumatic pressure allows both extension

and the presentation of variable compliance to the environment.

Both the cable and other actuation styles are remote actuation strategies where the bulk of the

mechanisms that is used for actuation are not located directly on the robot. This is because the use of

actuators located directly on the robot, as in conventional designs, proves to be extremely complicated

and inefficient to implement for these types of robots.



Table 2.1 architecture properties of continuum robots in previous works

Classification criteria

Extrinsic Intrinsic Hybrid

In Series Not in

series

Hydraulic/pneu

matic

SMA Other

Actuation

Series Not in

series

[ANDERS

ON 67]

[HIROSE

93]

[HANNAN

01]

[SIMAAN

04]

[WENDLA

NDT 94]

[WILSON 93]

[OHNO 00, 01]

[AOKI 02]

[BAILLY 04a]

[SUZUMORI

92] [DAVIES

91, LANE 99]

[CIESLAK

99] [IKUTA

88]

[FUKUDA

89][MAED

A 96]

[ARAMAKI

95]

[MINETA

01]

[LIM 96]

[DARIO 02]

[KALLIO 98]

[IVANESCU

95]

[KORNBLU

H 98]

[JONES

04]

[IMMER

GE 95]

There are also other continuum style robot designs that are based on more conventional robot

construction techniques. [PALJUG 95] presented the JPL Serpentine Robot in his work. The robot was

based on the serial connection of five uniquely designed actuatable two degree of freedom joints.

[CHIRIKJIAN 92] presented a 30 degrees of freedom, planar robot. The design was based on a

variable geometry truss system composed of ten identical, three degrees of freedom truss modules.

According to the backbone and actuation type, Table 2.1 summarizes the different works in this field

presented in this chapter.

2.2.4 The key advantage of continuum robot compared with discrete

manipulator

It is important to note why it is useful to distinguish between continuum style and hyper-

redundant designs. Hyper-redundant robots are usually defined as having many more actuatable

degrees of freedom than the number of degrees of freedom of the robot’s workspace. However,

continuum style robots do not have to fit this definition. Continuum style manipulators can exhibit a

large number of degrees of freedom, but not all of these degrees of freedom are directly actuated.



Therefore, it is possible to have a continuum robot that is not technically a hyper-redundant robot. The

design difference between conventional manipulators and continuum style manipulators is that the

conventional manipulator is a serial connection of actuated joints. That is, every joint on the robot is

actuated, and it is then rigidly connected to the next joint. On the other hand, continuum style

manipulators are not designed this way. Considering a three degree of freedom section, the traditional

approach would be to actuate all three joints, thus obtaining three actuated degrees of freedom. The

continuum style robot might provide a torque at tip of the robot, and then some type of coupling, i.e.

springs, could be used to transmit the torque to the three joints. Thus, the available degrees of freedom

are coupled in such a way that there is only one actuated degree freedom. Though this seems at first to

be counterproductive, the kinematics generated by this configuration proves to be very beneficial in

exploration, i.e. our application of exploring the whole colon.

A simple example is when the robot needs to reach around an obstacle, see figure 2.8 in

[HANNAN 01]. The discrete manipulator must provide actuation to all three of the joints to reach

around the obstacles, but the continuum robot can achieve the same motion with only one actuator

instead of three. Expanding this concept to hyper-redundant robots with many extra degrees of

freedom, then one can see a key benefit of continuum robots. The complexity of the mechanical

design, and the control for all of the actuators for a conventionally designed hyper-redundant robot

would be extremely difficult to implement. Many of the same configurations can be achieved using a

continuum robot design, but the design can be greatly simplified over that of a conventional style

manipulator.

Figure 2.8 Obstacle example: a) Discrete manipulator b) continuum manipulator



2.3 Design of EDORA II

2.3.1 Introduction

In chapter 1, the problems of a conventional colonoscopy have been discussed in detail. The

conventional colonoscope is a flexible, snake-like medical instrument to diagnose the colon. But the

insertion of colonoscope requires the physician to exert forces and rotations at the shaft outside the

patient thus causing the discomfort and pain to the patient due to pressure on and stretching of the

intestinal walls. Endoscopists need a long period of training before they can do the examination by

themselves. In order to solve these problems, automation of colonoscopy has been studied to lessen

the pain to the patient and reduce the complexity of operation. This work has been summarized as two

aspects:

• The autonomous locomotion part which makes the robot propels itself into the colon.

• Design of automatic bending distal end for colonoscope.

From the overview, we know that the most popular robotic colonoscopy is the inchworm-based

locomotion mechanism [PEIRS 00][ PEIRS 01][DARIO 97][BURDICK 94]. But this type of motion

needs to clamper the colon wall in order to advance through the colon. Since the colon is soft and

flexible and it can move with the colonoscope, this problem is a great challenge during a real

colonoscopy. The first one is the efficiency of the advancement, the other one is the possible pain to

the colon wall. The plausible solution for this problem is to apply strong force so that the robot can

clamper the colon firmly and can generate the reliable advancement. However, such a solution will

cause pain to the patient. Although [MENCIASSI 01, KUMAR00] tried to improve the efficiency of

clamping, the solution will need to be tested in more experiments to know its reliability.

However, another challenge for the conventional colonoscopy is the adjustment of the distal

end to the right direction for the progression. Also, many researchers [DARIO, BURDICK94, PEIRS

00, KUMAR 00] have proposed several design schemes for the bending tip which is integrated into

the whole robotic colonoscopy system. [KUMAR 00] used vision-based path-planning method to

guide the colonoscope. Thus the procedure can greatly reduce the possibility of contact with the colon

wall. Inspired by the efficiency of navigation and some discussion with surgeons, we have decided to

focus our research on the design of a robotic manipulator which can automatically guide the

introduction of the colonoscope and not so much on how to help the surgeons during the progression

of the colonoscope.

This solution will completely avoid the disadvantages of the self-propelled robotic

colonoscope and will greatly reduce the workload of the surgeon. Thus our goal is to design and

implement an intelligent robotic head which is able to avoid the contact with its environment while



guiding the progression during the colonoscopy. For that purpose, the movement of the head should be

controlled automatically to be positioned at the center of the intestine.

The research carried out in the field of the previous robotic colonoscopy brought us interesting

ideas for the design of a bending robotic manipulator. Several kinds of robotic manipulators have been

designed for automatic steering and guiding. These robotic manipulators belong to the continuum

robot in the classification from [DAVIES 99]. The continuum robot has more advantages than discrete

robots for the intervention and exploration in the constrained environments that need more flexibility

and dexterity. It can achieve many more degrees of freedom and can have very complicated

movements through the combination of the several actuations. These features are just what we needed

in the design of a robot colonoscope. The state of the art continuum robot in section 2.2 allows us to be

familiar with several techniques for designing continuum robots. Several structural designs have been

implemented for various applications, such as grasping, tubular exploration and endoscopic

exploration.

Before an actuation strategy can be adopted, there are two main properties that must be

addressed. The first consideration is that of structural support. This structure will provide enough

bending stiffness to determine the overall shape of the manipulator for backbone-based manipulator.

These manipulators are called extrinsic form continuum manipulator, including the hybrid from, can

be found in [ANDERSON 67] [HIROSE 93] [HANNAN 01] [SIMAAN 04] [WENDLANDT 94]

[JONES 04] [IMMERGE 95]. Two methods can be found to provide enough stiffness. One is the

backbone structure with extensibility [JONES 04] [IMMERGE 95] and the other is the backbone

structure without extensibility [ANDERSON 67] [HIROSE 93] [HANNAN 01] [SIMAAN 04]

[WENDLANDT 94]. As for the pneumatic/hydraulic manipulator, the material properties are an

important factor for determining the deformation shape. This kind of actuator is often based upon three

identical cylindrical elements, such as bellows or uniform tubular construction. The movements of the

assembly, the direction of motion and the orientation of the bending plane are controlled by the

pressure differentials amongst the elements. The common approach is to use bellows [WILSON 93]

[OHNO 00, 01] [AOKI 02] [BAILLY 04a] [LANE 99] [THOMANN 02]. Another approach is to use

silicone rubber [SUZUMORI 92]. For this kind of design, extension in the radial direction is greater

than axial extension. The geometry of the cross section must be such that large axial elastic deflection

is possible prior to the onset of plastic deformation in the radial direction. The material properties of

the elements, in particular the elastic modulus, strongly influence the deflected profile of the device.

For a given applied bending moment, the deflection is larger for materials of lower elastic modulus.

Although SMA-based manipulator has been studied in some works [CIESLAK 99] [IKUTA 88]

[FUKUDA 89][MAEDA 96] [ARAMAKI 95] [MINETA 01] [LIM 96] [DARIO 02], its low

efficiency and slow response time will effect its application that requires a real-time response.



2.3.2 Previous works on robotic colonoscopy in the project of the

laboratory

Figure 2.9 a: EDORA b: EDORA-01

In this project, [THOMANN 03b] has done a lot of work on the analysis of clinical

requirements. Working together with surgeons, a proposition has been forwarded to design a

new distal end while the manual progression of colonoscope is kept. This new distal end is in

accordance with MIS by minimizing the contact between the colonoscope and the interior

boundary of the colon, and to make the progression of the colonoscope easier for the surgeon.

According the specifications, a new prototype of the robot manipulator called EDORA (Distal

End with Automatic Orientation) has been designed and implemented.

Bellows are chosen to be the components of EDORA because of its inherent advantages.

The principal properties of the bellows are their resistance against pressure, temperature and

corrosion. Also, they have good sealing, a natural elasticity, and a long life cycle without

maintenance. For reasons of convenience of tests, further modification and construction, the first

prototype has been constructed with the scale 2 for the final tool. Now its diameter is 26mm and

the length is 90mm, shown in Figure 2.9a.

It is made up of 3 columns of bellows and 2 plates at each end. Three columns bellows

dispose 120 degrees among each other. Furthermore, a supporting plate at the middle of the

robot makes the robot into one whole unit. This produces a simple, compact, lightweight

mechanism which contains no moving parts and yet can generate motion with up to three

degrees of freedom, allowing both the direction and magnitude of tip movement to be

controlled. The internal pressure of each chamber is independently controlled using pneumatic



servovalves from Atchley Controls. When the same pressure is applied in three chambers, the

actuator elongates and, in the case of uneven pressure, it can bend by many degrees. Preliminary

experiments showed that this structure has too much stiffness to keep the movement and there is

also some vibration. So a layer of covering rubber is used to cover the exterior of the EDORA.

Thus the new one is called EDORA-01, shown in Figure 2.9b. More details can be found in

[THOMANN 03b].

Figure 2.10 Photo of the complete assembly of the experimental platform

Figure 2.11 the scheme for the complete assembly of the experimental platform

Besides to the design of EDORA, another important contribution of this dissertation is

the experimental system which is used to test the feasibility for the final application in the real

colonoscopy. To achieve this purpose, an emulation platform was constructed to test the



capability of EDORA to position itself automatically in the middle of a circle representing the

interior wall of a testing tube. The transverse movements of colonoscope during the progression

in the colon is emulated by using a table which can move in two directions (X,Y) manually. The

bottom of EDORA is fixed on that table, so the EDORA can move in the same way as the table

does. The three distance sensors are placed on a 50 mm diameter circle emulating the colon, and

the magnet is a 16 mm diameter which is placed on the top of EDORA, shown in figure 2.10.

Figure 2.11 gives the photo of the whole system.

Since Hall-effect sensors cannot be used to test its performance for traversing a pipe,

three optical fibers were integrated at its end to measure the position, shown in figure 2.12.

Figure 2.12 Photo of EDORA-01 integrated with three optical fiber sensors

With the new position sensors, the experiment was done in a tube with a diameter of

35mm. The advance of the EDORA in the tube was performed manually, just like during a real

colonoscopy, with a velocity of about 4cm/sec. Every time, the three measurements vary but

never go below 1.7 mm. This fact shows that the EDORA never touches the wall of the tube

while progressing in the tube.

In all, these experimental results demonstrated that the objectives of the dissertation

have been achieved: to design a distal end for the colonoscope in order to automatically avoid

the contacts between the colonoscope and the intestine wall. The manipulation of colonoscope

is kept for the surgeon. As for the experimental platform and EDORA prototype, inexpensive

standard materials were utilized to implement required functions. The preliminary results are

promising, however it is necessary for us to design a new tool with the size suitable for the real

colonoscope. The size of scale 1 of this distal end should thus be achieved for further

application.



2.3.3 The problems and shortcomings of EDORA

Although the preliminary experiments have shown that the EDORA satisfied the purpose

of specifications defined in the dissertation [THOMANN 03b], experiments have also

demonstrated some essential weakness to be improved. EDORA can only have a maximum

bending angle of 23o, which is not far enough to traverse the original colon bend in a real

operation. Furthermore, the diameter of EDORA is 26mm, which is more than the average

diameter of the colon 20mm [KUMAR 00]. Therefore some efforts need to be made to reduce

the size of the bendable tip.

Preliminary research carried out immediately showed the difficulties of miniaturizing

the EDORA. In the same way, the miniaturization of EDORA will generate the problem of

choosing distance sensors. So in this section, the general idea of miniaturization of EDORA

will be firstly discussed and the following section will focus on the construction of the EDORA

II.

In order to reduce the size of the EDORA, several possible solutions have been

considered as the following:

- continue to use metal bellows, but of reduced size or to redesign a new structure

with the same mechanism as EDORA.

- in order to obtain an automated distal aspect with a good bending property, the

simplest solution is to use the current coloscope while motorizing the axes of the

knobs operated manually by the surgeon to bend the colonoscopic tip.

Figure 2.13 FMA in silicone rubber designed by [SUZUMORI 91]



In fact, no matter which design is used, the new version of EDORA must have a higher

performance than the current one. To achieve this purpose, another solution using a new

structure has been considered. Since the main weakness of EDORA is its small bending angle

compared to the cable-driven distal end of conventional colonoscope, the movement with the

bigger bending angle is the most important consideration. To implement a larger bending angle

it is necessary to take into account the satisfactory performance of the automatic movements of

the EDORA and therefore we must keep the same structure and mechanism for the new

manipulator while using another type of actuator than the bellows.

So we had the idea of designing, by molding, a new distal end using silicone rubber

which has the same structure as the EDORA. This idea was first forwarded by [SUZUMORI

91]. In his works, he described the construction and operation of small low pressure silicon

rubber Flexible Micro-Actuator (FMA), shown in figure 2.13. Three parallel chambers were

molded directly into a single cylindrical unit. To have a good bending effect, integral nylon

reinforcing fibers around the circumference of the cylinder avoided radial expansion while

allowing the actuator to stretch longitudinally.

2.3.4 Construction of EDORA II

The efforts for the new EDORA has began in the last part of the dissertation

[THOMANN 03]. And the first version of silicone EDORA II was made just to test which kind

of silicone rubber can be used as the components for the new structure. In order to achieve this

purpose, two important aspects should be considered. The first one is, as described earlier, that

this new structure should have enough stiffness to support the movement of the EDORA, and

the second one is that this structure should have a wider range of bending movements than

EDORA with a reduced size.

Figure 2.14 Photo of the new prototype in silicone rubber

With suggestions from industrial providers, we have chosen the silicone rubber with the

suitable Modulus Young for our application. Using silicone rubber, the experimental prototype

has been constructed, as shown in figure 2.14. This new prototype has three cylindrical rooms



disposing 120° among each other in its circumference. Its bending movement can be obtained

by applying pressure differentials by pneumatic servovalves in three rooms. This prototype has

a diameter of 15mm and the length of 80 mm. By using this new version of EDORA, the

preliminary experiments have been carried out and the results are encouraging. By providing

the relative pressure of one bar in one room, this prototype can bend by as much as 170 degrees.

So the first version of EDORA gave us much inspiration and reference for a new

prototype of EDORA II. Then, some simulations were done in ABAQUS to optimize the

structure of new EDORA II, thus the second version of EDORA was designed and developed

with full consideration on integrating power supply tubes and surgical tools into the whole

colonoscope. The main structure of EDORA II has three cylindrical rooms and a cylindrical

central hole. The central hole provided the space for the camera and the power supply tube.

Furthermore, there is space in the center preserved for surgical tools to pass through during

therapy. This prototype has a diameter of 17 mm on the exterior and the interior hole is 10 mm

with a length of 100 mm, shown in figure 2.15.

Figure 2.15 The structure of new manipulator

Experimental tests done on this version of EDORA showed a good bending property. In

fact, by applying the relative pressure of 2 bars in a room, it can bend almost 120°. However, it

was also observed that this prototype demonstrate big disadvantages. There is noticeable

expansion in the radial direction while the bending movements are achieved, shown in figure

2.16.

After some experiments, the problems and requirements for designing EDORA are

further analyzed for better design. Since the final goal of designing new EDORA is to reduce its

exterior diameter while preserving its good bending property. The principal constraints needs to

be considered:

- The diameter of the interior hole of the manipulator which must be equal to or

bigger than 8 mm according to the conventional colonoscope: the proper size will

allow full integration of the power supply tubes and of the surgical tools into the

whole colonoscope.



- The structure made of silicone rubber without enough thickness at the chamber wall

will generate radial expansion which is not suitable for the bending motion, shown

in figure 2.16.

Figure 2.16 The radial expansion because of thin wall of the room

Thus, there is only one possibility to minimize the diameter of our prototype, which is to

reduce the diameter of the power rooms. However, this solution presents several shortcomings:

- By decreasing the surface of the rooms, more pressure needs to be applied to obtain

the required bending angel, for example, more than 3 bars for a bending angle of

90°. In terms of safety considerations, this situation is not what we want.

- With more pressure, there are more possibilities of radial expansion.

Since silicone is an elastic material, the stiffness of the manipulator will depend on its

constructed structure and the quantity of the matter. If the concentration of the solid silicone

rubber is high in the consistency of the manipulator, the more stiffness there is. Thus more

force, etc., more pressure (F= PS) is needed to make it bend. On the one hand, a possible

solution for this problem is to reduce the quantity of the matter which comprises the

manipulator. On the other hand, a compromise should be made between the reduction of the

matter and the room wall with minimum thickness of the manipulator that keeps the room from

expanding.

Therefore, only the substance between the rooms at the circumference is decreased, and

this decrease in substance will reduce the stiffness of the manipulator to a proper level without

changing the thickness of each chambre.

Thus three supplementary chambers next to actuation chambers are made in the new

structure of EDORA II. The diameter of each room is also 2 mm in length and this has been

obtained in order to decrease the quantity of matter between the room while keeping the exterior

diameter and the thickness of each room unchanged.

For the simplicity of molding these forms, simple cylindrical rooms are utilized for the

design of our prototype, shown in figure 2.17.



Figure 2.17 Structure of EDORA II

So now this new structure has six rooms of 2 mm at its circumference. Three rooms are

used to generate active bending movement by applying pneumatic pressure to them, while the

other three rooms are just used for the stiffness. The exterior diameter of EDORA is 17mm and

the interior hole is 8mm with a length of 107 mm and its weight is 20g.

Figure 2.18 A: The assembly of the EDORA II with colonoscope; b: a: The top view of EDORA II with all the

accessories in the central room

With this version of EDORA II, figure 2.18 shows the assembly of EDORA II (the white one)

with the conventional colonoscope. From the top view, the camera, optical fibers and the other

surgical tools can be found in the central room of EDORA II, shown in figure 2.18 b. With the

relative pressure of 2 bar in one chamber, EDORA II can bend till 120° . Figure 2.19 shows the

deflected shape of EDORA II with pressure in one chamber.



Figure 2.19 EDORA II in inclination

2.3.5 Discussions and Conclusions

EDORA II has demonstrated satisfactory results, however there is room to improve the

performance of new EDORA in our following research. One task of future research lies in the

structure design of EDORA. A feasible solution is to use some new shape, for example, the

shape of the eclipse to get a better bending effect. A combination of several shapes can also be

tested for the effective bending movement. Another important focus of research lies in the

research of the physical property of silicone rubber. Deep knowledge of the physical property of

silicone rubber will improve the possibility of choosing proper stiffness by using a different

proposition of a different matter. Moreover, finite element simulation software –ABAQUS will

provide a good platform to optimize the structure design by combining these two aspects. A first

study has been made in collaboration with the department of Material Engineering of the INSA

of Lyon to determine the principal characteristics of silicone rubber. Thus, the finite element

analysis method was used to model and simulate the deformation of a new tip.

With further study on the property of silicone rubber and structure optimization it will

be possible be obtain a manipulator with the diameter of 13mm for application in the real world.



Figure 2.20 The scheme of control system

2.4 Control system for EDORA II

For the actuation of EDORA II, three servovalves of jet-pipe type ATCHLEY (3a, 3b

and 3c) are used to control the pressure of each room of EDORA II. Figure 2.20 shows the

arrangement and the corresponding electrical interface. The analogue valve supplies a

pneumatic pressure to each room that is directly proportional to a current input varying between

–20 to 20 milliamps. The output of the pneumatic control valve is varied depending upon the

command received from the computer (6). The control valve then provides the corresponding

pressure to the relevant room of EDORA. On the other hand, the instantaneous pressure of each

room of EDORA is sensed at the output of three ATCHLEY servovalves, and the air power

supply is provided by the compressor (1) and is filtered by 5 micron filter (2).

Figure 2.21 The scheme of electric interface



Integration box (5) is comprised of a power supply, a voltage/current converter for

valves and corresponding amplification circuits. This part plays the role of the electric interface

between the computer and DS1005 PPC Board from Dspace company, shown in figure 2.21.

The DS1005 PPC Board is one of dSPACE’s processor boards that form the core of dSPACE’s

modular hardware. Processor boards provide the computing power for the real-time system and

also function as interfaces to the I/O boards through PHS-Bus. There are two classes of boards

used for digital conversion from digital to analog and vice versa. DS2103 Multi-Channel D/A

Board provides digital-to-analog signal conversion. It has been designed to generate control

signals for three servovalves. The board features 32 14-bit D/A channels. Inversely, the DS2002

Multi-Channel A/D Board has been used for digitizing analog input signals of the pressure of

EDORA feedback control.

Figure 2.22 Control program in Simulink

For real-time control of EDORA II, DS1005 PPC Board has been integrated into

Matlab/Simulink real-time workshop which provides “hardware-in-the-loop” prototype. This

integration allows for rapid prototyping of the control system design in the translation from

simulation studies to the real robot. Figure 2.22 shows Simulink program for controlling the

movement of EDORA.



In order to facilitate the adjusting of the control variables, the control desk associated

with DS1005 PPC Board provides an excellent interface to implement this purpose. Figure 2.23

shows this human-machine interface.

It is necessary to mention that pressure control of each chamber of EDORA II is not the

focus of this dissertation. So a simple Proportional-Integral (PI) controller is designed to

regulate the pressure for experiments of kinematics in the next chapter.

Figure 2.23 Control desk of DSpace

2.5 Conclusion

Firstly, the review of the continuum robot has been given. Continuum robots are new

robotic manipulators without rigid joints, that are is different from the conventional rigid-link

robots. Their special feature and structure design have been analyzed from three classifications

of a continuum robot: extrinsic continuum robot, intrinsic continuum robot and hybrid

continuum robot. In addition to this, its advantages are discussed as compared to the

conventional robot manipulator. This profound analysis allowed us to have a reference to design

a new robotic tip for colonoscopy.

Secondly, analysis and design of EDORA II are presented in details. Previous works

done on robotic colonoscopy in the same project were first presented. Then the problems and

shortcomings of EDORA are analyzed and new design considerations are given based on these

results. After that, a new robotic manipulator for colonoscopy, called EDORA II is designed by

using silicone rubber. It has an exterior diameter of 17 mm and is about 100 mm in legth. Its



weight is about 20g, which is very suitable for exploration procedures. The preliminary

experiments presented an excellent bending effect. EDORA II can bend up to 120° when the

pressure is augmented to 2 bars.

Finally, the hardware and software for the whole control system are described. DS1005

PPC Board and corresponding I/O interfaces were used for real-time control of EDORA II.

In the following chapter, the kinematics analysis of EDORA will be detailed.

Chapter 3 Kinematics Analysis for Continuum Robotic Manipulator: EDORA II


Chapter 3

Kinematics Analysis for Continuum Robotic

Manipulator: EDORA II



3

CHAPTER 3 ........................................................................................................................................................ 83

KINEMATICS ANALYSIS FOR CONTINUUM ROBOTIC MANIPULATOR: EDORA II.................... 83

3.1 Three essential parameters characterize the deflected shape of EDORA II ...................................... 85

3.2 Kinematics analysis using basic geometry ........................................................................................ 88 3.2.1 Basic geometry for kinematic analysis ...................................................................................................... 88

3.2.2 Derivation of orientation angle of the bending plan .................................................................................. 89

3.2.3 Derivation of bending angle α .............................................................................................................. 90

3.2.4 Summary ................................................................................................................................................... 91

3.3 Derivation of kinematics relating to internal pressure of each chamber ........................................... 91 3.3.1 The experiment setting and results ............................................................................................................ 92

3.3.2 Relationship between deflected shape with relation to the applied pressure of each chamber .................. 93

3.4 Velocity Kinematics.......................................................................................................................... 94 3.4.1 Non-redundant case ................................................................................................................................... 95

3.4.2 Redundant case.......................................................................................................................................... 95

3.5 Inverse velocity kinematics ............................................................................................................... 96

3.6 Validation of kinematic model .......................................................................................................... 98 3.6.1 The sensor choice and experimental setup................................................................................................. 99

3.6.1.1. The miniBIRD.......................................................................................................................... 99 3.6.1.2. Experimental setup................................................................................................................. 100

3.6.2 Validation of bending angle..................................................................................................................... 101

3.6.3 Validation of orientation angle ................................................................................................................ 103

3.6.4 Verification of correlation among each chamber..................................................................................... 105

3.6.5 Estimation of a correction parameter....................................................................................................... 106

3.7 Conclusions..................................................................................................................................... 109



Since continuum robotic manipulators do not have link joints, which makes them

completely different from the conventional robot, new problems are thus generated on how to

build the kinematics of these manipulators along with the corresponding control problems.

Some modeling of hyper-redundant robotic manipulators inspired the works of the continuum

robot manipulator. [CHIRIKJIAN 92] [CHIRIKJIAN 93] [CHIRIKJIAN 94] [CHIRIKJIAN 95]

proposed a great deal of theory that had laid the foundation for the kinematics of hyper-

redundant robots. Most of their research used modal analysis to describe the robot’s kinematics.

Their sophisticated analysis was based on treating the robot as a “string”. However, their modal

approach does not take into account the physical constraints of real continuum robots, and the

resulting algorithms are complex, non-intuitive, and hard to integrate with conventional robot

algorithms. [MOCHIYAMA 98], [MOCHIYAMA 99] and [MOCHIYAMA 01] presented

research in the area of kinematics and the shape correspondence between a hyper-redundant

robot and a desired spatial curve. The idea was to define the kinematics of the robot by

associating it with a predetermined curve. [GRAVAGNE 00a] [GRAVAGNE 00b]

[GRAVAGNE 00c] applied several different approaches for analyzing the kinematics of

continuum robots in his work. Most recently, by using the concept of Denavit-Hartenberg for

the modeling conventional robotic manipulator, [HANNAN 01] proposed an innovate method

for the continuum style robotic manipulator- the Elephant trunk. His model utilized the concept

of constant curvature sections, and incorporated them through the use of differential geometry

into a modified Denavit-Hartenberg procedure to determine the kinematics. The importance of

this is that the Denavit-Hartenberg procedure is the most commonly used approach for

determining the kinematics of conventional robots. Thus, the theory and analysis method of the

conventional robot can be easily used for modeling and controller design. Then, [BYRAN 05]

improved the virtual Denavit-Hartenberg-based approach by optimizing the virtual joint

configurations for the modeling of a Multi-Section Continuum Robot: Air-Octor [BYRAN 05].

In this chapter, a different kinematic model will be developed for EDORA II in detail.

3.1 Three essential parameters characterize the deflected shape of

EDORA II

As was presented in several textbooks [SCIAVICCO 00], joint angles and link lengths

provide an easy and physically realizable description of a conventional robotic manipulator

when embedded in its kinematic model, but for continuum robotic manipulators this no longer

holds true due to the continuous nature of their design. In a continuum robot, most often, there

are no clearly identifiable places where joints and links can be defined. Therefore, a kinematic

model must use new parameters that more appropriately describe the continuous and deflected

shape of continuum robots. The kinematic model introduced here strongly uses the concept of



curvature to describe the shape of the manipulator. This concept is very natural for curved

structures, and is exploited in the work [HANANN 02]. In this dissertation, the concept of

curvature has been extended to three dimensions, but the kinematics of EDORA II will be

developed directly from the direct geometry between the actuator inputs and the chosen

parameters without using D-H transformation. Thus three parameters (figure 3.2) have been

chosen to characterize the position and the orientation of the tip with respect to the bottom of

the manipulator as done in our previous prototype EDORA [THOMANN 03] [CHEN 03]

[CHEN 04]. They are described as the following:

• L is the virtual length of the center line of the robotic manipulator;

• α is the bending angle in the bending plane;

• φ is the orientation of the bending plane;

It is worth to note that [SUZUMORI 92], [LANE 99],[BAILLY 04b], [HANNAN 03],

[GRAVAGNE 02] also used almost the same set of parameters for modeling of proper

continuum robots.

Figure 3.1 Schema for the complete assembly of the experimental platform



Figure 3.2 Frame of reference for EDORA II

Consider an EDORA II shown in Figure 3.1. It is supported at the bottom end in a way such that

it stands vertically and the top end can move freely with the pressure variation in three

chambers. Figure 3.2 shows the frame of reference O-XYZ which is fixed at the base of the

manipulator. The X-axis is the one which passes by the center of the bottom end and the center

of the chamber 1. The XY-plane defines the plane of the bottom of the actuator, and the z-axis

is orthogonal to this plane. The frame of reference UVW is attached to the top end of the

manipulator. So the bending angle α is defined as the angle between the O-Z axis and O-W

axis. The orientation angle φ is defined as the angle between the O-X axis and O-T axis, where

O-T axis is the project of O-W axis on the plan X-O-Y. The notation is explained as the

following:

i: chamber index, i = 1, 2, 3

R: radius of curvature of the center line of the robotic tip

iL : arc length of the ith chamber

L0 : initial length of the chamber

iP : pressure in the chamber i

S : effective surface of the chamber

iR : radius of curvature of the ith chamber

ε : stretch length of the virtual center line

iL∆ : the stretch length of the ith chamber



3.2 Kinematics analysis using basic geometry

Controlling the deflected shape of the manipulator requires a kinematic model relating

deflected shape in terms of extension and bending to actuator inputs. This section will focus on

the deflected shape to the length of three chambers. Given three known chamber length, 1L , 2L ,

3L and the constant distance r from the center of EDORA II to the center of each pressurized

chamber, the following equations allow computation of the resulting length L , the bending

angle α and the orientation angle φ .

Two assumptions have been done for simple analysis to obtain the kinematics of EDORA II.

• There is no axial displacement;

• The load effects are ignored;

• Even though EDORA II can bend till 120°, the bending angle α is now constrained between

0 / 2< α ≤ π because the deflected shape will be more complicated when the bending angle

is more than 90°.

With three presumptions, the deflected shape of EDORA II at the bending moment is

assumed to be an arc of a circle, just as most researchers did for their continuum robots

[SUZUMORI 92][LANE 99][BAILLY 04b][HANNAN 03][GRAVAGNE 02]. In addition to

this, three chambers have the same bending angles except the different arc lengths.

3.2.1 Basic geometry for kinematic analysis

Given the bending angle at the bending moment, then the key relation for the kinematics

is given as:

i iL R= α (3.1)

or given in the form of the stretch length of virtual central line:

i i 0 i i 0L / R (L L ) / R (L ) / Rα = = + ∆ = + ε (3.2)

and

i i 0L L L∆ = − Angle iφ is defined as the angle of bending plan relative to the chamber i, shown in Figure 3.3

1

2

3

- 120

120

φ = φ⎧⎪ φ = − φ⎨⎪ φ = − − φ⎩

(3.3)

By using these angles, the radius of curvature R of the chamber i can be represented as:

i iR = R - rcos( )φ (3.4)

and :



i iL = L - rcos( ) α φ (3.5)

where r is the distance between the center of the manipulator and the center of the chamber .

Figure 3.3 Definition of angle iφ

As 3

ii 1

cos 0=

φ =∑ , one can be deduced from (3.4) and (3.5) that:

31

i3i 1

R R=

= ∑ (3.6)

31

i3i 1

L L=

= ∑ (3.7)

These two equations explain that the deformation of the manipulator on the whole is the average

of three chambers.

3.2.2 Derivation of orientation angle of the bending plan

By using equation (3.5) in the first two chambers, then

1 1 2 2L r cos( ) L r cos( )+ α φ = + α φ (3.8)

replacing (3.3) and expanding the cosines, then α and L can be obtained

2 1L L2r 3cos 3 sin

−α =

φ − φ (3.9)

2 11

2(L L )cosL L

3cos 3 sin− φ

= +φ − φ

(3.10)

continuing using (3.5) on chamber 3 and replacing α and L,

2 13 1

2(L L )(3cos 3 sin )L L

3cos 3 sin− φ − φ

= +φ + φ

(3.11)

ϕ

r2

3

1r1

r2

r3

Plan ),,( ztOdefined by φ

x



finally the orientation angle tan φ is found as:

2 3 1 2 3a tan 2( 3(L L ),2L L L )φ = − − − (3.12)

the function atan2(y,x) is a function used in MATLAB which extends the function a tan(y / x) in

the quadrant for the point (x,y). It has the following form:

a tan(y / x) if x 0 and y 0a tan(y / x) - if x 0 and y 0

at an 2(y,x) a tan(y / x) if x 0 /2 if x = 0 and y>0

- /2 if x = 0 and y<0

+ π < ≥⎧⎪ π < <⎪⎪= >⎨⎪π⎪

π⎪⎩

(3.13)

It is worth noting that the equation (3.12) is undetermined when 2 33(L L ) 0− = and

1 2 32L L L 0− − = , i.e. 1 2 3L L L= = . In this case, the manipulator demonstrates the pure

elongation, which will not be discussed in this chapter.

3.2.3 Derivation of bending angle α

Then by combining equation (3.2) and equation (3.4), R is obtained:

3

ii 1

13

i 1i 1

LR r cos

L 3L

=

=

= φ−

∑

∑ (3.14)

Since there exists the following trigonometric relation:

2 2

xcos(a tan 2(y, x)) , (x,y) (0,0)x y

= ∀ ≠+

(3.15)

Then the radius of bending shape is finally described as:

3

ii 1

L

r LR

2==

ξ

∑ (3.16)

and 2 2 2L 1 2 3 1 2 1 3 2 3L L L L L L L L Lξ = + + − − − (3.17)

After R is obtained, by using (3.2) and (3.7), the bending angle α can be easily gotten:

L23rξ

α = (3.18)



3.2.4 Summary

In this section, the kinematics model based on basic geometry has been dealt with. The

concept of kinematics is just used for easy understanding with an analogy to the conventional

robot. Knowing the lengths of three chambers, analytical expressions for three system

parameters which characterize the deflected shape at the bending moment are the following:

2 3 1 2 3a tan 2( 3(L L ),2L L L )φ = − − − (3.12)

L23rξ

α = (3.18)

11 2 33L (L L L )= + + (3.7)

Written in matrix form, it can be expressed as:

X f (q)= (3.19)

where TX ( , ,L)= α ϕ , T1 2 3q (L ,L ,L )=

with the assumption that the deflected shape is an arc of a circle, so the expression in the

Cartesian coordinate system can be easily calculated from figure 3.4:

Lx= (1- cos ) cos

Ly = (1- cos ) sin

Lz = sin

⎧ α φ⎪ α⎪⎪ α φ⎨ α⎪⎪ α⎪ α⎩

(3.20)

3.3 Derivation of kinematics relating to internal pressure of each

chamber

Since the deflected shape of the manipulator is controlled by the pressure differential of

three chambers by using servovalves, the kinematic model obtained in the above section should

be developed relating to the three input pressure of chambers. So the relationship between the

length variation of each chamber and the applied pressure in the chambers is determined, then

the deflected shape is determined relating to the applied pressure.



3.3.1 The experiment setting and results

Considering that the exterior forces to the top end of EDORA are negligible and that the

mass is negligible, the stretch length of each chamber is assumed to be proportional to the

pressure variation in each chamber as is done by many researchers on continuums robots. In our

case, however, the strong nonlinearity relating the stretch length of chamber to the pressure

variation has been shown in preliminary experiments. This relationship is described as:

i iL f (P )∆ = (3.21)

where if (P ) is the nonlinear function of iP and this section will deal with this function through

experiments.

The stretch length of a single chamber is measured when the pressure is applied from 0

bar to the pressure maximum which can make the actuator bend 90°, while the pressures of the

other two chambers are kept at zero bar. For precise measurements, the pressure in the chamber

is kept constant by using a closed-loop controller. Since the deformation of the each chamber is

an arc of a circle, it’s difficult to find a suitable sensor to measure the arc length. A simple

method is then used to measure the length of the chamber. When the chamber is stretching

under pressure, a fine string is placed right outside the stretched chamber, so the length of the

string can be considered approximately as the length of the chamber.

Results obtained from experiments proved that there is a non-linear behavior (hysteresis)

between the pressure and the stretch length of each chamber (figure 3.4). A polynomial model is

thus used to approximate the measurements. A criteria based on the norm of the mean error is

used to select the order of each polynome fitting the data. This analysis shows that a second

order polynomial approximation allows to fit significantly the actual data as is shown on figure

3.4. The corresponding results can be written as:

21 1 1min 1 1max

1 1 11 1min

22 2 2min 2 2max

2 2 2

3.8P + 24.8P if P P PL f (P )0 if P <P

4.4P +15.7P if P P PL f (P )0

⎧ < <⎪∆ = = ⎨⎪⎩

< <∆ = =2 2min

23 3 3min 3 3max

3 3 33 min

if P <P

7.9P 33.9P if P P PL f (P )0 if P <P

⎧⎪⎪⎪

⎧⎪ ⎪⎨ ⎨

⎪⎪ ⎩⎪ ⎧− + < <⎪⎪∆ = = ⎨⎪ ⎪⎩⎩

(3.22)

Where iminP (i = 1, 2, 3) is the threshold of the working point of each chamber and their values

equal 1min

2min

3min

P = 0.7 barP = 0.8 barP = 0.8 bar

⎧⎪⎨⎪⎩

and imaxP (i = 1, 2, 3) is the maximum pressure that can be applied to each chamber.



0.6 0.8 1 1.2 1.4 1.6 1.8 2 -5

0

5

10

15

20

25

30

35

40

Pressure of the chamber (bar)

Dis

plac

emen

t of t

he c

ham

ber (

mm

)

The relationship between the input pressure and the stretch l h

Measurement of Chamber 1Measurement of Chamber 2Measurement of Chamber 3Elongation/pressure model of chamber 1Elongation/pressure model of chamber 2Elongation/pressure model of chamber 3

0.7 Bar

0.8 Bar

Figure 3.4 The model between the stretch length and the applied pressure of each chamber

3.3.2 Relationship between deflected shape with relation to the applied

pressure of each chamber

After the relationships have been determined between the stretch length of the each

chamber and the applied pressure, then the corresponding length of each chamber under the

pressure variation is expressed as the following:

1 0 1 0 1

2 0 2 0 2

3 0 3 0 3

L L L L f (P )L L L L f (P )L L L L f (P )

= + ∆ = +⎧⎪ = + ∆ = +⎨⎪ = + ∆ = +⎩

(3.23)

By inserting equation (3.23) into (3.7) and (3.12), then new equations are obtained as followed: 1

0 1 2 33L L (f (P ) f (P ) f (P ))= + + + (3.24)

2 3 1 2 3a tan 2( 3(f (P ) f (P )), 2f (P ) f (P ) f (P ))φ = − − − (3.25)

In the same way, the equation (3.18) can be transformed as: 2 2 2

L 1 2 3 1 2 1 3 2 3f (P ) f (P ) f (P ) f (P )f (P ) f (P )f (P ) f (P )f (P )ξ = + + − − − (3.26)

But for the sake of easier distinction, it is named as: 2 2 2

P 1 2 3 1 2 1 3 2 3f (P ) f (P ) f (P ) f (P )f (P ) f (P )f (P ) f (P )f (P )ξ = + + − − − (3.27)

so the bending angle can be expressed in applied pressure:

P23rξ

α = (3.28)



And the matrix form of this model is given by :

Pf ( )=X q (3.29)

where T( , ,L)= α φX , Tp 1 2 3(P ,P ,P )=q .

3.4 Velocity Kinematics

In the conventional joint/link robotic manipulator, differential kinematics are presented

to explain the relationship between the joint velocities and the corresponding manipulator linear

and angular velocity. This is used to coordinate the motion of the individual joints in order to

move the manipulator in a specified direction at a specified speed. Analogous to this concept in

conventional kinematics analysis, the velocity kinematics for continuum robots can be written

as:

J =X q (3.30)

where ∈X is the task space vector, i.e. position and/or orientation, q is the joint space vector,

J is the Jacobian matrix and is a function of q , and the dot implies differentiation with respect

to time, i.e. ddt

. For the manipulator EDORA II, the task space is represented by the position

and orientation of the end-tip of EDORA II:

( )T L= α φX

and the joint space vector is chosen as the applied pressure in each chamber because of the final

control implementation is needed to calculate the applied pressure in three chambers.

( )Tp 1 2 3P P P=q

So there are two methods to calculate the Jacobian matrix using the analytical technique. The

first one is to directly use the differentiation of the direct kinematics function with respect to the

joint variables expressed in pressure, i.e. equation (3.23) (3.24) and (3.27); the other option is

through an indirect method. Firstly, the differentiation of the direct kinematics function with

respect to the joint variables expressed in length of each chamber, i.e. (3.7) (3.12) and (3.18),

then partial derivative relating the length to the applied pressure of each chamber will be

calculated. The Jacobian is shown as:

X LJL P

∂ ∂=∂ ∂

(3.31)

In this thesis, the second method is used to calculate the Jabobian matrix for calculation

considerations.



3.4.1 Non-redundant case

By choosing the task space vector X , it’s natural to compute the Jacobian matrix via

differentiation of the direct kinematics function with respect to the joint variables. This method

is called analytical technique and the Jacobian matrix can be written as:

31 2

1 1 2 2 3 3

31 2

1 1 2 2 3 3

31 2

1 1 2 2 3 3

LL L

L P L P L PLL L

J L P L P L P

LL LL L L L P L P L P

⎛ ⎞∂∂ ∂∂α ∂α ∂α⎜ ⎟∂ ∂ ∂ ∂ ∂ ∂⎜ ⎟⎜ ⎟∂∂ ∂∂φ ∂φ ∂φ= ⎜ ⎟

∂ ∂ ∂ ∂ ∂ ∂⎜ ⎟⎜ ⎟∂∂ ∂∂ ∂ ∂⎜ ⎟⎜ ⎟∂ ∂ ∂ ∂ ∂ ∂⎝ ⎠

(3.32)

according to equations (3.24) (3.25)and (3.28), and knowing that (x,y) (0,0)∀ ≠ :

2 2

g(x, y) f (x, y) f (x, y) g(x, y)x xa tan 2(f (x, y),g(x, y))

x g(x, y) f (x, y)

∂ ∂−∂ ∂ ∂=∂ +

(3.33)

and from equation(3.23), the velocity kinematics is obtained:

' ' '1 2 3 2 1 3 3 1 21 2 3

L L L

' ' '2 3 3 1 1 21 2 3

L L L

' '1 2

2L L L 2L L L 2L L Lf (P ) f (P ) f (P )

3r 3r 3rd

3(L L ) 3(L L ) 3(L L )d f (P ) f (P ) f (P )

2 2 2dL

1 1f (P ) f (P ) 3 3

− − − − − −ξ ξ ξ

α⎛ ⎞− − −⎜ ⎟φ =⎜ ⎟ ξ ξ ξ⎜ ⎟

⎝ ⎠

1

2

3'

3

dPdPdP

1 f (P )3

⎛ ⎞⎜ ⎟⎜ ⎟

⎛ ⎞⎜ ⎟⎜ ⎟⎜ ⎟⎜ ⎟⎜ ⎟⎜ ⎟⎜ ⎟⎝ ⎠

⎜ ⎟⎜ ⎟⎜ ⎟⎝ ⎠

(3.34)

where 2 2 2L 1 2 3 1 2 1 3 2 3L L L L L L L L Lξ = + + − − − , is defined by the equation (3.17) and '

if (P ) is the

derivative of if(P ) (i = 1, 2, 3) concerning to the pressure iP (i = 1, 2, 3) .

3.4.2 Redundant case

Although three parameters ( )T Lα φ can uniquely determine the position and the

orientation of end-tip of EDORA II in the task space, it’s difficult to place a sensor to measure

the length of virtual center line. However, if only orientation vector ( )T α φ is considered, there

is not much effect on the application of tubular exploration because the orientation is enough

for the guidance. In this case, the robotic manipulator is functionally redundant because the

number of components of task space is less than the number of degrees of freedom. Thus the

velocity kinematics are given as:



r r pJ =X q (3.35)

where Tr ( )= α φX

then Jacobian matrix with relation to the three pressure in the chamber is given as following:

31 2

1 1 2 2 3 3r

31 2

1 1 2 2 3 3

LL L

L P L P L PJ

LL L

L P L P L P

∂∂ ∂∂α ∂α ∂α⎛ ⎞⎜ ⎟∂ ∂ ∂ ∂ ∂ ∂⎜ ⎟=⎜ ⎟∂∂ ∂∂φ ∂φ ∂φ⎜ ⎟⎜ ⎟∂ ∂ ∂ ∂ ∂ ∂⎝ ⎠

where rJ is the submatrix of J constructed by the first two rows and three columns of J , this is

' ' '1 2 3 2 1 3 3 1 21 2 3 1

L L L2

' ' '2 3 3 1 1 231 2 3

L L L

2L L L 2L L L 2L L Lf (P ) f (P ) f (P ) dP3r 3r 3rd

dPd 3(L L ) 3(L L ) 3(L L ) dPf (P ) f (P ) f (P )

2 2 2

− − − − − −⎛ ⎞⎛ ⎞⎜ ⎟ξ ξ ξα⎛ ⎞ ⎜ ⎟⎜ ⎟=⎜ ⎟ ⎜ ⎟⎜ ⎟φ − − −⎝ ⎠ ⎜ ⎟⎜ ⎟⎝ ⎠⎜ ⎟ξ ξ ξ⎝ ⎠

(3.36)

3.5 Inverse velocity kinematics

Equation (3.30) and Equation (3.35) provided the velocity of task space and angular

velocity of the robot manipulator as a linear function of joint velocities based on the non-

redundant case and redundant case. The inverse velocity kinematics is concerned with the joint

velocities and with the velocity of task space. Namely, given a desired manipulator velocity, we

find the corresponding joint velocities that cause the robot manipulator to move at the desired

velocity. In the case of non-redundant configuration, since the Jacobian matrix is square matrix

of n order and the determinant is not null, so it’s easy to calculate directly the inverse matrix of

J . So the inverse Jacobian matrix is given the following relation: 1J −=q X (3.37)

In the case of a redundant manipulator with respect to a given task, equation (3.35), the

inverse kinematic problem admits infinite solutions. This suggests that redundancy can be

conveniently exploited to meet additional constraints on the kinematic control problem in order

to obtain greater manipulability in terms of manipulator configurations and interaction with the

environment. Some typical applications using redundancy are referenced here:

• Obstacle avoidance [MACIEJAWSKI85];

• Mechanical joint limits [LIEGEOIS 77];

• Joint actuator power consumption [VUKOBRATOVIC 84];

• Avoidance of kinematic singularities [YOSHIKAWA 85a], [YOSHIKAWA 85b],

[KLEIN 87], [ANGELES 88], [CHIU 88];



A viable solution method is to formulate the problem as a constrained linear

optimization problem. [WHITNEY 69], in his pioneering work on resolved-rate control,

proposed to use the Moore-Penrose pseudoinverse of the Jacobian matrix as: T T 1

p J (J (JJ ) )+ −= =q X X (3.38)

The pseudoinverse Jacobian matrix has a least squares property that generates the minimum

norm joint velocities.

By revising the pseudoinverse minimum-norm solution, a more general solution (3.35)

and is given by:

p J [I J J]g+ += + µ −q X (3.40)

where I is the identity matrix and g is an arbitrary joint velocity vector. The homogeneous term

[I J J]g+µ − is the null space projection of the solution of (3.37). The null space solution only

generates motion in the “joint” space of the manipulator, and will produce zero movement in

task space of the robot. This null space motion is also known as the self motion of the robot.

It is worth discussing the way to specify the vector g for a convenient utilization of

redundant degrees of freedom. A typical choice is :

Ta

w(q)g k ( )q

∂=∂

where ak 0> and w(q) is a second objective function of the joint variables. Since the solution

moves along the direction of the gradient of the objective function, it attempts to locally

maximize its compatibility to the primary objective (kinematic constraint). The typical objective

functions are:

• The manipulability measurement, defined as

Tw(q) det(JJ )= (3.41)

which vanishes at a singular configuration; thus, by maximizing this measure, redundancy

is exploited to move away from singularities.

• The distance from mechanical joint limits, defined as 2n

i iave

iM imi 1

q q1w(q)2n q q=

⎛ ⎞−−= ⎜ ⎟−⎝ ⎠∑ (3.42)

where iMq and imq denotes the maximum and minimum joint limit and iq−

the middle value

of the joint range; thus, by maximizing this distance, redundancy is exploited to keep the

joint variables as close as possible to the center of their ranges.

• The distance from an obstacle, defined as

p,ow(q) min || p(q) o ||= − (3.43)



where o is the position vector of a suitable point on the obstacle (its center, for instance, if

the obstacle is modeled as a sphere) and p is the position vector of a generic point along the

structure; thus, by maximizing this distance, redundancy is exploited to avoid collision of

the manipulator with an obstacle.

For the robot manipulator EDORA II, there is a mechanical limit range for the elongation of

each chamber and the corresponding pressure applied into the chamber .

1min 1 1max 1min 1 1max



L L L , P P P

L L L , P P P

L L L , P P P

≤ ≤ ≤ ≤

≤ ≤ ≤ ≤

≤ ≤ ≤ ≤

In order to avoid this case, the objective function is constructed to be included in the

inverse Jacobian algorithm, equation (3.40), as the second criteria. This objective function

evaluate the pressure difference between the applied pressure in the chamber and the average

pressure iaveP applied in the chamber . So the cost function is expressed as the following:

23i iave

iM imi 1

P P1w(q)3 P P=

⎛ ⎞−= ⎜ ⎟−⎝ ⎠∑ (3.44)

we can then minimize w(q) by choosing:

1 1ave 2 2ave 3 3ave2 2 2

1 2 3 1M 1m 2M 2m 3M 3m

P P P P P Pw w w 2g grad w(q) = P P P 3 (P P ) (P P ) (P P )

⎛ ⎞⎛ ⎞ − − −∂ ∂ ∂= = ⎜ ⎟⎜ ⎟∂ ∂ ∂ − − −⎝ ⎠ ⎝ ⎠ (3.45)

So the solution pq to Equation (3.40) meets the minimization of two criteria simultaneously:

• Minimum norm joint velocities through J+X ;

• Secure the pressure variation of each chamber relating to the average pressure is minimal.

Now that the inverse velocity kinematics is developed, the kinematic control of can be

implemented based on (3.40) to control the position/orientation of EDORA II.

3.6 Validation of kinematic model

As described before, a theoretical kinematic model has been developed for EDORA II,

the next logical step is to provide experimental verification of the model. Since the kinematics

of EDORA II have been described as the relationship between the deflected shape and lengths

of three chambers (three pressures of each chamber), the validation of kinematics needs to have

a sensor to measure the deflected shape, i.e. the bending angle, the arc length and the

orientation angle. So this section first presents sensor choice and its experimental setup for



determining system parameters, then presents the verification of static kinematic model using

these experimental configurations.

3.6.1 The sensor choice and experimental setup

As for most continuum style robots, due to the dimension and the inability to mount

measurement device for the joint angles, the determination of the manipulator shape is a big

problem. Although there are several different technologies that could help solve this problem

with big one, such as [HIROSE 02], but they are difficult and costly to implement on a micro-

robot. Since a Cartesian frame has been analyzed with relation to the deflected shape

parameters, an indirect method is used to for the purpose of validation of kinematics with the

position measurement in 3D. With comparison and contrast of different 3D sensors, a

“miniBIRD” sensor is used for experimental validation.

Figure 3.5 MiniBIRD position and orientation measurement system

3.6.1.1. The miniBIRD

MiniBIRD is a six degree-of-freedom (position and orientation) measuring device from

Ascension Technology Corporation. A miniBIRD consists of one or more Ascension Bird

electronic units, a transmitter and one or more sensors, see figure 3.5. It offers full

functionality of our other DC magnetic trackers, with miniaturized sensors as small as 5mm

wide. Table 3.1 shows the characteristics of miniBIRD [Ascension 02]. The real-time

measurement can be easily integrated with Dspace 1005 card, described in chapter 2, through

serial communication.



Degree of Freedom 6 (position and orientation)

Range ±76.2cm

Accuracy Position: 1.8mm

Orientation : 0.5°

Resolution Position:0.5mm

Orientation: 0.1° @ 30.5cm

Measure rate Up to 120 measurements /second

Figure 3.6 Experimental setup of miniBIRD sensor

3.6.1.2. Experimental setup

The bottom of EDORA II is bounded to a fixture and the sensor is placed on the top of

EDORA II, shown in figure 3.6. The transmitter is placed at a stationary position. Thus the

position and orientation of top-end of EDORA II is read directly from the sensor –receiver- with

relation to the transmitter, and then the position of top-end of the manipulator with relation to

the bottom of the manipulator is calculated indirectly through reference transformation, shown

in figure 3.7.

Table 3.1. Characteristics of miniBIRD 500



Figure 3.7 Reference Transformation for calculating the position of top-end relative to the bottom end of EDORA II

3.6.2 Validation of bending angle

Since the bending can be expressed concerning to the length of the each chamber or

concerning to the pressure of each chamber, so two cases are used to validate bending angle.

The first one is to use the length of chamber to directly calculate the bending angle. Since the

length of each chamber under pressure has been measured as described in 3.3.1 :

1 0 1 0 1

2 0 2 0 2

3 0 3 0 3

L L L L f (P )L L L L f (P )L L L L f (P )

= + ∆ = +⎧⎪ = + ∆ = +⎨⎪ = + ∆ = +⎩

(3.23)

so the bending angle can be easily calculated by using Equation (3.18) relating the bending

angle to the chamber length.

L23rξ

α = (3.18)

where 2 2 2L 1 2 3 1 2 1 3 2 3L L L L L L L L Lξ = + + − − −

Receiver

Transmitter Reference Frame

+ X

+ Z+ Y

Measurement ofthe sensor

Position of top-end relative tothe bottom end



Then, from equation (3.28),

P23rξ

α = (3.28)

where 2 2 2P 1 2 3 1 2 1 3 2 3f (P ) f (P ) f (P ) f (P )f (P ) f (P )f (P ) f (P )f (P )ξ = + + − − −

the bending angle is calculated with relation to the three pressure input of three chambers

respectively.

1 1.2 1.4 1.6 1.8 2 2.2 2.4 x 10 5

0

10

20

30

40

50

60

70

80

90 Verification of kinematic

Pressure in one chamber

Ben

ding

ang

le

the model in pressurethe experimental measurementsthe model in length

Figure 3.8 Comparisons of bending angle with relation to the chamber length and chamber pressure

The comparison of two results in figure 3.8 shows that the bending angle concerning the

chamber length and the chamber pressure respectively has the same characteristics. In order to

directly check the validation of the theoretical model, the miniBIRD sensor is used to measure

directly the bending angle under the corresponding pressure and the results are shown in figure

3.8. Compared with other two lines, the curve of the directly measured bending angle has some

difference with the other two curves obtained by indirect methods. This difference is explained

to be the measurement error of the chamber length brought on by the imprecise manual

measurements.

To validate the position of the end-tip in the bending moment, another experiment has been

carried out. The miniBIRD sensor is used to measure the displacement of end-tip with relation

to the reference coordinate. Theoretically, the position in the space can be easily calculated

(Equation 3.20) when the bending angle is measured.



Lx= (1- cos ) sin

Ly = (1- cos ) cos

Lz = sin

⎧ α φ⎪ α⎪⎪ α φ⎨ α⎪⎪ α⎪ α⎩

Then the comparison of theoretical and experimental results are shown in figure 3.9.

1 1.2 1.4 1.6 1.8 2 2.2 2.4 x 10 5

0

10

20

30

40

50

60

70

Presssure in the room (Pascal)

X (m

m)

the experimental measurementsthe theoretical model in pressure

Figure 3.9 Position comparison of end-tip of EDORA II

From this figure, the results are satisfactory because the experimental data has a good

agreement at each pressure point except the first several points. Again, these errors can be

explained by the fact that the weight of the sensor has much more effect with lower pressure in

the chamber than higher pressure in the chamber. Finally, the comparison results of the two

experiments proved greatly that the kinematic model for the bending angle gives good

performances.

3.6.3 Validation of orientation angle

Another important parameter to be verified is the orientation angle, expressed in the

equation (3.25) relating to the three pressure points 1 2 3(P , P , P ) :

2 3 1 2 3a tan 2( 3(f (P ) f (P )), 2f (P ) f (P ) f (P ))φ = − − −



Since the miniBIRD can not measure the orientation angle directly, indirect methods are

required to check the orientation angle. From Equation (3.20), we can obtain the orientation

angle with relation to the XY frame coordinate.

Lx= (1- cos ) cos y arctan( )

L xy = (1- cos ) sin

⎧ α φ⎪⎪ α ⇒ φ =⎨⎪ α φ⎪ α⎩

So by using miniBIRD to measure the XY frame coordinate, the experiments are easily done to

check the orientation angle. The pressure combinations of three chambers are used are the

following:

1 2 3

2 1 3

3 1 2

1 2 3

g(P ), with P P 0 (1)g(P ), with P P 0 (2)g(P ), with P P 0 (3)g(P P ), with P 0

φ = = =φ = = =φ = = =φ = = =

2 3 1

3 1 2

(4)g(P P ), with P 0 (5)g(P P ), with P 0 (6)

⎧⎪⎪⎪⎪⎨⎪⎪φ = = =⎪

φ = = =⎪⎩

This pressure combinations, theoretically, will follow 6 principal orientation angles (0°, 60°,

120°, 180°, 240°, 300°) with the bending angle varying from 0 to the maximum in the plane (x-

o-y). Figure 3.10 shows theoretical and experimental results. From this figure, the 6 orientation

angles are close from the theoretical values.

-50 -40 -30 -20 -10 0 10 20 30 40 50 -60

-40

-20

0

20

40

60 Validation of orientation angle

X (mm)

Y (m

m)

Experimental measurements

Simulation

Figure 3.10 Comparison of orientation angle



3.6.4 Verification of correlation among each chamber

Section 3.6.2 and 3.6.3 validated the bending angle and orientation angle separately in a

static way. The special motion that EDORA II can generate results from the pressure

differentials among each chamber, this is to say, the interaction of each chamber. So it is

necessary to check this mutual interaction among each chamber. To achieve this goal, sinuous

signals of pressure with 120° delay among each servovalve with a definitive velocity are

employed to make EDORA II turn around its vertical axis (see the experimental setup figure

3.7) to see the mutual interaction of each chamber. By using miniBIRD, the coordinates of

endpoint of EDORA II can be easily obtained in XOY plane. Thus the comparison between

these coordinates and the coordinates obtained from the simulation of kinematic model

(Equation 3.20, 3.29) allows us to verify if there is any mutual interaction among each chamber

elongation.

Two comparisons are then proposed (figure 3.11). Three sinuous signals of pressure

with an amplitude of 0.4 bar and an offset of 0.9 bar are applied in the chambers of the

prototype. The path of the endpoint of EDORA II is in a form of a triangle(figure 3.11a )

because these actuators of EDORA II work in their nonlinear zone. Three sinuous signals of

pressure with an amplitude of 0.4 bar and an offset of 1.2 bar are applied in the chamber of

EDORA II. In this case, EDORA II works in the linear zone and has the approximate movement

of a circle (figure 3.11 b).

-50 -40 -30 -20 -10 0 10 20 30 40 50-40 -30 -20 -10

0 10 20 30 40 Comparison between the model without correction and the experiment

X (mm)

Y (m

m)

SimulationExperiment

-60 -40 -20 0 20 40 60 80-60

-40

-20

0

20

40

60

X (mm)

Y (m

m)

Comparison between the model without correction and experiment

SimulationExperiment

(a) (b)

Figure 3.11 Simulation et experimental results of the movement of the endpoint of EDORA II

The lines in the outer layer are the simulation results from the kinematic model relating XY

coordinates to the corresponding pressure of each chamber without mutual interactions of three

chambers. The three chamber models used are the following:



21 1 1min 1 1max

1 1 11 1min

22 2 2min 2 2max

2 2 2

3.8P + 24.8P if P P PL f (P )0 if P <P

4.4P +15.7P if P P PL f (P )0

⎧ < <⎪∆ = = ⎨⎪⎩

< <∆ = =2 2min

23 3 3min 3 3max

3 3 33 min

if P <P

7.9P 33.9P if P P PL f (P )0 if P <P

⎧⎪⎪⎪

⎧⎪ ⎪⎨ ⎨

⎪⎪ ⎩⎪ ⎧− + < <⎪⎪∆ = = ⎨⎪ ⎪⎩⎩

(3.22)

The difference between the simulation of the model and the experimental results show that there

exists an interaction among each chamber when the motion of top-end of EDORA II is

achieved. Therefore, additional parameters need to be added to reflect this behavior.

3.6.5 Estimation of a correction parameter

In this section, new parameters will be chosen to represent the mutual interactions

among each chamber. They will account for the coupling effect of stretching of one chamber to

that of the other two chambers. Thus 6 parameters are added to describe this effect:

k12 = mutual stiffness that determine the effect of P2 on the length of the chamber 1






Here, it is assumed that the hysteresis of each chamber actuator is negligible, and then 6 mutual

stiffnesses will be reduced to one parameter as the geometry of EDORA II is symmetric.

Thus the property of each actuator is represented as the following:

1 1 1 2 2 3 3

2 2 2 1 1 3 3

3 3 3 1 1 2 2

L f (P ) k(f (P ) f (P ))L f (P ) k(f (P ) f (P ))L f (P ) k(f (P ) f (P ))

∆ = + +⎧⎪∆ = + +⎨⎪∆ = + +⎩

then the coefficient k is obtained by minimizing the difference between the operational

coordinates (Xs, Ys) measured by miniBIRD and the operational coordinates (Xm, Ym) obtained

by simulation of the geometrical model (Equation 3.20, 3.29), figure 3.12.



System

Min J

Model XmYm

YsXs

Figure 3.12 Optimisation model

And the cost criteria is chosen as :

2 2 2 2m m s sJ(k) || X (k) Y (k) X (k) Y (k) ||= + − +

Then the coefficient k obtained is 0.3.

1 1 1 2 2 3 3

2 2 2 1 1 3 3

3 3 3 1 1 2 2

L f (P ) 0.3(f (P ) f (P ))L f (P ) 0.3(f (P ) f (P ))L f (P ) 0.3(f (P ) f (P ))

∆ = + +⎧⎪∆ = + +⎨⎪∆ = + +⎩

then figure 3.13 and figure 3.14 present the results with the correction parameter of two cases.

0 5 10 15 20 25 300.4 0.5 0.6 0.7 0.8 0.9

1 1.1 1.2 1.3 1.4

Time ( t )

Pres

sure

(bar

)

Pressures in three chambres (nonlinear)

-40 -30 -20 -10 0 10 20 30 40-40

-30

-20

-10

0

10

20

30Comparison between the simulation of corrected model and experiment

X (mm)

Y (m

m)

Simulation of corrected kinematic model

Experimental result

(a) (b)

e 3.13 Comparison between the result of simulation with correction parameter (continuous line) and experimental result

(a) pressure group for three chamber of EDORA II (b) the endpoint of EDORA II in the plane of XY.



0 5 10 15 20 25 300.7 0.8 0.9

1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 Pressures in three chambres

Time (t)

Pres

sur (

bar)

Chambre 1 Chambre 2 Chambre 3

-40 -30 -20 -10 0 10 20 30 40 50-50

-40

-30

-20

-10

0

10

20

30

40

50Comparison between simulation of corrected model and experiment

X (mm)

Y (m

m)

Simulation of corrected kinematic model

Experimental result

a b

e 3.14 Comparison between the result of the simulation with a correction parameter (continuous line) and experimental

result (a) pressure group for three chambers of EDORA II (b) the endpoint of EDORA II in the plane of XY.

To check the uniformity of this coefficient within its total work zone of EDORA II, three other

experiments have also been carried out to validate this coefficient for each case. Three sinuous input

pressures with an amplitude ranging from 0.1 bar to 0.3 bar are applied to three chambers of EDORA

II. By using the improved kinematic model with the corrected coefficient, the comparison shows that

this coefficient reflected the same mutual effect among each chamber during its total work zone of

EDORA II including the dead zone. Figure 3.15 and figure 3.16 present the comparison results of two

cases. Results prove right the assumption that there exists interaction between each chamber.

-40 -30 -20 -10 0 10 20 30 40 -40

-30

-20

-10

0

10

20

30 Results of different pressure ampitude (one part in the deadzone)

X

Y

Amplitude of 0.4 bar Amplitude of 0.3 bar

Amplitude of 0.2 bar


Figure 3.15 Verification of corrected with different pressure input (dead zone)



-40 -30 -20 -10 0 10 20 30 40 50 -50

-40

-30

-20

-10

0

10

20

30

40

50

X coordinnate (mm)

Y co

ordi

nnat

e (m

m)

Results of different pressure amplitude

Amplitude of 0.4 bar Amplitude of 0.3 bar



Figure 3.16 Verification of corrected with different pressure inputs (linear zone)

To summarize, the experimental results verified that there exists interaction among each

chamber when the motion of top-end of EDORA II is generated. Since three chambers are

identical, the coefficients determined from non-linear algorithm are the same for three chambers

within their work zones.

3.7 Conclusions

In this chapter, we have detailed the study of kinematics of EDORA II. Three geometric

parameters are chosen to determine the position/orientation of top-end of EDORA II. With the

assumption that the deflected shape is an arc of a circle and the effects are ignored, then we

have established the forward kinematic model of EDORA II relating these three parameters to

the length of three chambers. Unlike other works on the linearity of the actuator, the non-linear

models of each chamber were obtained through experiments. Thus, the kinematics relating to

three system parameters to three pressures were then determined. Based on the forward

kinematics analysis, the velocity of kinematics is then studied from two cases: non-redundant

and redundant. In the case of redundant manipulation with relation to the chosen variables:

bending angle and orientation angle in the task space, inverse velocity kinematics is studied.

Experiments have been done to validate the bending angle and orientation of EDORA II



respectively. To check if there is any mutual interaction among each chamber, sinuous signals

of pressure with 120° delay among each chamber with a definitive velocity were employed to

make EDORA II turn around its vertical axis. Experimental results showed that there is mutual

interaction among each chamber. Thus a new correction parameter was chosen to represent this

effect and its coefficient was determined through a non linear optimization and validation.

Chapter 4 Dynamic Modeling and Parameters Identification

Gang Chen Thèse en Robotique Chirurgicale / 2003 Institut National des Sciences Appliquées de Lyon 111

Chapter 4

Dynamic Modeling and Parameters Identification


Gang Chen Thèse en Robotique Chirurgicale / 2003 Institut National des Sciences Appliquées de Lyon 112

4

CHARPTER 4 DYNAMIC MODELING AND PARAMETERS IDENTIFICATION......................... 11111 4.1 Dynamic analysis of EDORA II system.......................................................................................... 113

4.1.1 Electro-pneumatic part ............................................................................................................................ 114 4.1.2 Mechanical part: ...................................................................................................................................... 115

4.1.2.1 Static behavior of EDORA II.......................................................................................................... 115

4.1.2.2 Dynamics of EDORA II ................................................................................................................. 117

4.1.3 The whole system.................................................................................................................................... 117 4.2 Parameter identification of dynamic behavior of EDORA II .......................................................... 118

4.2.1 Introduction to identification of continuous-time system ........................................................................ 118 4.2.2 Formulations of parameter estimation of continuous-time Model ........................................................... 119 4.2.3 Levenberg-Marquardt algorithm and its numerical implementation........................................................ 121

4.3 Experiment design for identification and its validation................................................................... 122 4.3.1 Experiment setting................................................................................................................................... 123 4.3.2 Data collection......................................................................................................................................... 123 4.3.3 Estimation results and its analysis ........................................................................................................... 125 4.3.4 Validation of identification results .......................................................................................................... 130

4.4 Conclusions..................................................................................................................................... 131



In the previous chapter, the kinematics of EDORA II has been developed relating the

position of the top-end to the pressure inputs of three chambers. This analysis permits the top-

end of EDORA II to stay at a specified location in the task space. Furthermore, differential

kinematics are considered to be able to allow the manipulator to move in a specified direction at

a specified speed. However, this is not enough for the real-time control of EDORA II in the

colon in view of the application environment. In order to get better performance of the

manipulator, the dynamic behavior of EDORA II will be analyzed in this chapter.

4.1 Dynamic analysis of EDORA II system

Continuum robots present a novel control problem in that the entire structure undergoes

elastic deformation and there are no joints to control or measure. Methods of direct

measurement of the manipulator end-point are required for reliable position control. However,

under the knowledge of the author, there isn’t any suitable sensors for measuring the

position/orientation directly. So in direct position models which relate internal bellow pressures

to deflected position via physical parameters have been proposed for controlling the single stage

of AMADEUS underwater robot manipulator [DAVIES 96][ARRICHIELLO 98]. Similarly, a

cable-based continuum robot might utilize kinematic models based on the cable length to infer

their position. The micro-manipulator system used proximity sensors to measure the orientation

of the supporting plate and hence obtain the micro-manipulator position [KALLIO 98]. There is

also other control methods, such as Tele-operation by using a joystick [IMMGEA 95].

It should be noted that these approaches only considered the kinematics without the

dynamics of a manipulator. This is a big weakness that influences the manipulation performance

of these continuum robots. Although, the structure of a continuum robot presents a compact

design and more dexterity, so far there hasn’t been much work done on the research of the

dynamics of a continuum robotic manipulator. The reason can be attributed to the fact that the

manipulator is a multi-input, multi-output system with a strong coupling among each chamber.

Since EDORA II belongs to the class of continuum robot, how to control its position

will determine the effect of the automation of colonoscopy. So far, there are two approaches:

one is kinematic control plus automatic path planing; the other one is also kinematic control but

with tele-operation through a joystick. The latter one, in fact, is an open loop system with the

operator to determine the desired path. Since the operation environment of colonoscopy is

unstructured and movable, the path planing will result in great change [BAILLY 04a]. On the

other side, the tele-operation control will need one person to operate it. So this control strategy

is not suitable for control of EDORA II because the physician needs to carry out the

introduction of the colonoscope. This would burden the work of the physician. As far as the

special requirements of the application of EDORA II are considered, we’ll discuss an alternative



control strategy and its dynamic modeling from the perspective of application in this thesis.

Since the requirement for the automatic navigation of introduction of a colonoscope described

in chapter 1 is to avoid touching the colon, it is more practicable to control the relative position

between the robot and the colon than the position relating to the base of EDORA II. Thus,

EDORA II can be equipped with three position sensors (chapter 5) for three chambers to

measure the relative position between EDORA II and the colon by controlling the position of

each chamber against the colon wall, EDORA II can stay far from the colon wall. Consequently,

the total system is separated into three independent subsystems. Each of them is composed of 2

parts: mechanical and electro-pneumatic parts (Figure 4.1).

Computer

Electro-pneumatic part

(V)DAC

Power supply

interfaceservovalve

(I)

CurrentMechanical part

EDORA II

(P) (x)

PressureDisplacement of the

top-end with respect to the vertical position

Figure 4.1 The schema of the dynamics of one servovalve and one chamber

4.1.1 Electro-pneumatic part

Three same servovalves are used to control the internal pressure in the chambers. The

control input of servovalves is the current I (-20 mA to 20 mA). The dynamics of electro-

pneumatic part, is thus concerned the control input (I) of servovalve with the pressure in the

chamber (P). The electro-pneumatic chain has the strong nonlinear behavior because of its

complicated physics. The detailed and deep research on the modeling of the dynamics of the

electro-servovalve can be found in [BAILLY 04a]. Here we can consider the dynamics of the

servovalve as a first order system [PRELLE 01 ][THOMANN 03b]. Let pH (s) the transfer

function of the electro-pneumatic part:

pP(s) kH (s)I(s) 1 s

= =+ τ

(4.1)

Where k and τ are respectively the static gain and the time constant of one servovalve.



4.1.2 Mechanical part:

4.1.2.1 Static behavior of EDORA II

Before dealing with the dynamics of EDORA II, the static behavior of EDORA II is first

discussed. As analyzed in the chapter 3, when the chamber is applied with pressure, the

chamber will stretch. Figure 4.2 gave the characteristics of the stretch length relating to the

pressure. Due to the special structure of EDORA II, a deflected shape will be obtained when the

chamber length stretches under the pressure. Thus there is a displacement of endpoint from the

vertical center of EDORA II, figure 4.3. This relationship between the chamber length and the

displacement will depend on the structure of EDORA II, the stiffness of manipulator and the

young modulus. Although the maximum displacement of endpoint can attain the position where

EDORA II has a bending angle with 90° as shown in chapter 3, the small displacement is

assumed to obtain the dynamics of each chamber subsystem. This assumption will be justified

from the fact that traversing the big bend of the tube is implemented step by step.

0.6 0.8 1 1.2 1.4 1.6 1.8 2 -5

0

5

10

15

20

25

30

35

40

Pressure of the chamber (bar)

Dis

plac

emen

t of t

he c

ham

ber (

mm

)

The relationship between the input pressure and the stretch length

Measurement of Chamber 1Measurement of Chamber 2Measurement of Chamber 3Elongation/pressure model of chamber 1Elongation/pressure model of chamber 2Elongation/pressure model of chamber 3

0.7 Bar

0.8 Bar

Figure 4.2 Static characteristics of three chambers (figure 3.4)



Therefore, dynamics of EDORA II is considered between the applied pressure and the

displacement of the top-end. As done in chapter 3 for kinematics, miniBIRD sensor is still used

to measure the displacement. The detailed experimental setting will be discussed later in this

chapter. In order to determine the gain of nonlinearity between the displacement of a top-end of

EDORA II, experiments have been done to measure the displacements of the top-end of one

chamber relating to its control current. Figure 4.6 shows that four different zones are divided to

get four different values of the static gain. In the following part, four cases will be considered

respectively for parameters estimation of the model.

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 0

5

10

15

20

25

30

Control current of servovalve ( mA )

Dis

plac

emen

t of t

he to

p-en

d of

ED

OR

A II

(mm

)

Relationship between the displacement of the top-end and the control current

Zone 1

Zone 2

Zone 3 Zone 4

Figure 4.4 Relationship between the displacement of the top-end of one chamber and its control input

Figure 4.3 The relationship between the chamber length

and the displacement of end-point

α

L R

x



4.1.2.2 Dynamics of EDORA II

As we have analyzed in 4.1.2.1, three actuators show nonlinearity between the input

pressure and the elongation (displacement). However, if we choose the working point at above

the minimal pressure of each chamber for small displacements, then Wiener models consisting

of a linear dynamic system followed in series by a static nonlinear element are used to represent

the nonlinear dynamic behavior of three actuators. The linear part is considered as the relation

between the small displacements and the input pressure. The static function is considered as the

gain corresponding to the pressure (current).

For the linear model of each actuator, a second order system is thus chosen to

characterize the linear behavior of the mechanical part of EDORA II without greatly reducing

the performance of EDORA II [THOMANN 03b]. The transfer function is represented as

followed:

2s n

m 2 2n n

X (s)H (s)P(s) s 2 s

ω= =+ ξω + ω

(4.2)

with :

nω : is the natural frequency of one chamber

ξ : is the damping coefficient

P : is the pressure of one chamber

sX : is the small displacement of one chamber along the vertical center of EDORA II.

4.1.3 The whole system

After determining the orders of the electro-pneumatic part and the linear element of the

mechanical part respectively as first order and second order system, then the linear part of one

chamber of EDORA II is considered as a third order system by combining two separated

subsystems (4.1) (4.2) and its transfer function is given by Equation (4.3).

s 0p m 3 2

1 2 3

X (s) bH(s) H (s)H (s)I(s) s a s a s a

= = =+ + +

(4.3)

Where 0 1 2 3[b ,a ,a ,a ] are the unknown parameters to be estimated.

The whole non-linear system is schematically represented in figure 4.5.



Linear part

I ( )mH s XPXs

Nonlinearity

Hp(s) ( )K I

Figure 4.5 Model for one chamber of EDORA II

where K(I) is the static nonlinearity relating the displacement of the top-end of EDORA II of

one chamber to its input current. Its value has been determined through static measurements

shown in figure 4.4.

4.2 Parameter identification of dynamic behavior of EDORA II

In section 4.1, we analyzed the dynamic characteristics through experimental analysis.

In this part, a direct continuous-time approach with non-linear optimization is utilized to

estimate the parameters of the linear part of the model.

4.2.1 Introduction to identification of continuous-time system

Identification of continuous-time (CT) models is considered important in various

disciplines such as economics, control, fault detection and signal processing. Early efforts in

identifying CT linear time-invariant (LTI) systems began with CT models in their native

continuous time domain. Subsequently, rapid developments in digital data systems and

computers caused a major shift in the approaches with a go-completely-digital trend. Discrete-

time (DT) became the working domain in the field of system identification and identification of

DT models from sampled input/output data became the main approach. The identification

techniques for DT models with discrete-time data are well documented [LJUNG 99]

[SODERSTROM 89] and widely applied. However, the last three decades have witnessed

considerable development in CT approaches to system identification from sampled data

[PINTELON 00][SODERSTROM 00][BASTOGNE 01][RAO 02].

Identification of continuous-time systems model from sampled data can be done using a

variety of techniques. In general, the existing methods are classified into two main categories:

direct and indirect approach [YOUNG 81][UNBEHAUEN 87][SINHA 91][UNBEHAUEN 87].

Indirect approach is to estimate from sampled data a DT model first and then convert it into a

CT model. Direct approaches: as the name calls, this method attempts to estimate parameters of



a continuous-time model directly from the sampled data. The result is an approximate

continuous-time model in which the parameters of the original continuous-time model are

retained. The basic characteristics of the direct approach are in handling of the non-measurable

time-derivatives by linear transformation on input/output signals. Once the transformations are

calculated, it is then possible to employ the existing abound estimation techniques that are used

for identification of discrete-time models.

4.2.2 Formulations of parameter estimation of continuous-time Model

As we have analyzed before, the general scheme for direct CT model identification can be

divided into two distinct stages, shown in figure 4.6 :

• The first stage is specific to CT model identification. It consists in applying a LT (linear

transformation) to the input/output data in order to avoid the differential issue.

• The second stage concerns the parameter estimation where most algorithms developed for

DT model identification can be used.

z(t)B( )A( )

ρρ +

+

LT LT

u*(t)

-

+

ε*(t) =y*(t) -ŷ*(t)

Criteria JEstimation algorithm

B( )A( )

ρρ

ŷ*(t)

v(t)

y(t)

y*(t)

u(t)

Figure 4.6 General schema of parameter estimation of continuous-time model

As for the identification problem specific to this thesis, a SVF (state variable filter)

method is just used as the linear transformation of differential terms. In the second stage, an

optimization algorithm of Levenberg-Marguardt method will be utilized to achieve the

parameter estimation.



The general approach of identification of the continuous-time model is represented in

figure 4.6 [URBEHAUEN 90][URBEHAUEN 97]. It includes the application of a linear

transformation (LT) on input/output signals in order to remove derivatives. Since the model

structure has been determined in 4.1, the Output Error model structure is used for the parameter

estimation of the model.

Considering a system model described by the differential equation between the input u and the

output y: 1

0 1 1 01

( ) ( ) ( ) ( )... ( ) ... ( )−

−−+ + + + = + +n n m

n n mn n m

d y t d y t dy t d u ta a a a y t b b u tdt dt dt dt

(4.4)

Where ia (i = 0…n) and ib (j = 0…m) are the parameters of the model.

Then the OE form is represented as

( , )( ) ( ) v(t) ( , )

B py t u tA p

θθ

= + (4.5)

Where the p operator is defined by:

i = 1, . . . , ni

ii

dpdt

(4.6)

The polynomes ( )A p and ( )B p are given by:

ni

n ii 0

ni

m ii 0

A(p) a p

B(p) b p

−=

−=

=

=

∑

∑ (4.7)

0 n 0 n[ ... b ... b ]a aθ = is the vector of unknown parameters and v(t ) is the white noise of the

system.

So the output errors to be minimized are then given by:

( )

( ) ( )

* * *ˆ( ) ( ) ( )ˆ( ) ( ) = LT v(t) + ( ) - ( )ˆ( ) ( )

ˆ( ) ( ) = LT v(t) + [ - ] ( )ˆ( ) ( )

t y t y t

B p B pu t LT u tA p A p

B p B p LT u tA p A p

ε = −

⎛ ⎞⎜ ⎟⎝ ⎠

(4.8)

A parameter estimation criterion is to minimize: N 1

*2

k 0J( ) (k)

−

=

θ = ε∑ (4.9)

where N is the observation numbers.

Then by solving the equation 0Jθ

∂ =∂

, then the solution to θ will be obtained.

And the derivative of the criteria ˆ( )J θ concerning the parameter θ has the expression as:



**

0* *

*

0

*

0

( ) 2 ( )

ˆ( ( ) ( )) 2 ( )

= -2 ( ) ( )

N

k

N

k

N

k

J kk

y k y kk

k kθ

εεθ θ

εθ

ε σ

=

=

=

∂ ∂=∂ ∂

∂ −=∂

∑

∑

∑

(4.9)

The function ( )kθσ is the sensibility function of ( )y k concerning with θ and have the

expression : *( )( ) y kkθσθ

∂∂

(4.10)

and the numerical implementation will be dealt with in the following section.

4.2.3 Levenberg-Marquardt algorithm and its numerical implementation

Since the output error of (4.5) is nonlinear in regard to the parameters to be estimated,

this is a nonlinear optimization problem. To estimate the parameters, there are several

optimization algorithms. Of these algorithms, the Levenberg-Margquardt algorithm combines

the speed of the Newton algorithm with the stability of the steepest decent method, and is thus

selected to perform our parameter estimation. The LM algorithm uses the following formula to

calculate weights in the subsequent iteration [BONNANS 97], as shown in figure 4.7: 2 1ˆ ˆ ˆ ˆ( 1) ( ) ( ( ) ) ( )i i J I Jθ θ θ µ θ−⎡ ⎤+ = − ∇ + ∇⎣ ⎦ (4.11)

where:

ˆ( )∇J θ and 2 ˆ( )∇ J θ are, respectively, the gradient and the second derivation of output error, µ

is the Marguardt parameter.

The two important calculation formulas of the numerical implementation are given in

[SCHOUKENS 91]. They are the gradient calculation: 1

*ˆ

0

ˆ( ) 2 ( ) ( ),N

kJ k kθθ ε σ

−

=

∇ = − ∑ (4.12)

and the Hessien calculation is as following when neglecting the second order terms: 1

2ˆ ˆ

0

ˆ( ) 2 ( ) ( ),−

=

∇ = ∑N

T

kJ k kθ θθ σ σ (4.13)

with 1 2 1

ˆ ˆ ˆ ˆ( ) [ ( ), ( ),..., ( )]+ +

=n m

k k k kθ θ θ θσ σ σ σ

and*

ˆ( )( ) ˆ

∂=∂i

i

y kkθσθ

, which is the output sensitivity function of parameters to be estimated.



Calculation of criteria J

Calculation 2J J ∇ ∇

Initialization(0) θ µ

Calculation 2 1( J + )−∇ µ

Calculation of (i 1)θ +

J( (i) J( (i 1)) θ < θ +

2(i) (i)

µ = µθ = θ

/ 2(i 1) (i)

i i 1

µ = µθ + = θ= +

NoYes

*| y(t) y (t) | Pr ecision− <

obtain θ

No

Figure 4.7 The Levenberg-Marguardt Algorithm

4.3 Experiment design for identification and its validation

In the section 4.2, the theory and implementation of identification of continuous-time

model has been analyzed in details. In this section, this theory will be tailored to our

identification problem to obtain system parameters.



4.3.1 Experiment setting

As we have described in chapter 3.6, the miniBIRD distance sensor is utilized to

measure the displacement of the top-end of EDORA II. The bottom of EDORA II is bounded to

a fixture and the sensor is placed on the top of EDORA II, shown in figure 4.8. The transmitter

is placed at a stationary position. By positioning well the transmitter in relation to the sensor,

the displacement top-end of EDORA II will be easily measured without a coordinate

transformation.

Another parameter to be considered is the input current which controls the servovalve to

get the desired pressures. The current measurement is obtained by computer through the A/D

converter.

Figure 4.8 The experimental setup

4.3.2 Data collection

For the conformity of the choice of the working point, we apply initial pressure to each

chamber to get a balanced point. Next, a combination of input current is applied to the chamber

as the exciting signals (figure 4.9). These input signals fall into four zones (figure 4.4)

respectively, which cover the whole working zone of the actuator. Figure 4.10 shows the input

data and output data for one chamber.



0 10 20 30 0

0.5

1

1.5

2

2.5Combination of current input

Time ( s )

Inpu

t cur

rent

( m

A)

Figure 4.9 Combination of current inputs of one chamber

0 10 20 30 40 -5

0

5

10

15

20

25

30

Time ( s )

Inpu

t / O

utpu

t (m

A /

mm

)

Data acquisition

Output data Input data

Figure 4.10 Input / output data of one chamber



4.3.3 Estimation results and its analysis

As shown in Equation (4.3), the linear part of one chamber is represented as a third

order system:

s 0p m 3 2

1 2 3

X (s) bH(s) H (s)H (s)I(s) s a s a s a

= = =+ + +

(4.3)

Where T0 1 2 3[b ,a ,a ,a ]θ = is the unknown vector of parameters to be estimated.

After removing the effect of static gain in the nonlinear part determined in section

4.1.1.1, parameters for each zone are estimated separately through the direct identification

approach developed in section 4.2. Thus, four transfer functions at each zone for the first

chamber of EDORA II are obtained. They are named as ( )iH s (i = 1, 2,3,4) (i is the ith zone of a

chamber of EDORA II ) as following:

1 3 2

2 3 2

3 3 2

4 3 2

2330H (s)s 3.2s 442s 931

2341H (s)s 3.6s 452s 1012

2364H (s)s 3.6s 454s 932

2298H (s)s 3.7s 400s 931

=+ + +

=+ + +

=+ + +

=+ + +

(4.14)

Figure 4.11 –4.14 shows the curve fitting and the number of iterations of four transfer

functions for small displacement. From each of these figures, it can be seen that the model

matches the experiment data well except that there are some errors in zone 4. This fact can be

attributed the measurement noise of the sensors at the big displacement of top-end of EDORA

II. At the same time, the result was obtained after 25 iterations from the bottom graph of each

figure. In order to verify that the identification results are the results of the global optimization,

different initial conditions are chosen to estimate these parameters again. Given the initial

parameters with a deviation of 5% and of 50 % from the final parameters, parameters and

iteration numbers are shown in Table 4.1. Results show that the L-M algorithm finds the same

result for each initial condition. The single effect is that the velocity of convergence will

become slower when the initial parameters deviate further from the final parameter. Thus it can

be said that this algorithm has a good convergence for global optimization and has a good

robustness.



Table 4.1 Robustness of the L-M algorithm

5% deviation 50% deviation Transfer

function of

each zone

Coefficients

Iteration

number

Coefficients Iteration

number

1H (s) 2330.24[1 3.16 442.86 931.28]

11 2330.24

[1 3.156 442.86 931.28]

16

2H (s) 2341.56[1 3.593 452.61 1012.32]

15 2341.56

[1 3.593 452.61 1012.32]

23

3H (s) 2364.56[1 3.64 454.1 932.4]

8 2364.58

[1 3.64 454.1 932.4]

13

4H (s) 2298.1[1 3.74 399.8 930.7]

10 2298.1

[1 3.74 399.8 930.7]

15

5 10 15 20 25 30 35 40 0

20

40

60

80

Number of iterations

Parameters evolution

20*lo

g10(

para

met

ers)

0 1 2 3 4 5-0.5

0 0.5

1 1.5

2 2.5

Time in seconds

Curve fitting using Levenberg-Marquardt algorithm

Inpu

t /O

utpu

t (m

A /

mm

)

experiment model input

den(4)=931.2811den(3)=442.8583den(2)=3.1566num(1)=2330.235

Figure 4.11 Identification results of Zone 1 ( input current from 0 ma to 0.8 ma)



5 10 15 20 25 30 35 40 0

20

40

60

80



20*lo

g10(

para

met

ers)

0 1 2 3 4 5 6 7 8 9 10 -0.5

0

0.5

1

1.5

Time in seconds


Inpu

t /O

uput

(mA

/ m

m)

experiment outputmodel outputinput

den(4)=1012.3127den(3)=452.614den(2)=3.5929num(1)=2341.5455

Figure 4.12 Identification results of Zone 2 ( input current from 0.8 ma to 1.2 ma)

5 10 15 20 25 30 35 40 0

20

40

60

80



20*lo

g10(

para

met

ers)

0 2 4 6 8 10 12 -0.5

0

0.5

1

1.5

Time in seconds


Inpu

t / O

utpu

t (m

A /

mm

)

den(4)=932.3586den(3)=454.0934den(2)=3.6357num(1)=2364.5441

experiment outputmodel outputinput

Figure 4.13 Identification results of Zone 3 ( input current from 1.2 ma to 1.6 ma)



5 10 15 20 25 30 35 40 0 10 20 30 40 50 60 70



20*lo

g10(

para

met

ers)

0 1 2 3 4 5 6 7 -0.5 0

0.5 1

1.5 2

Time in seconds


Inpu

t /O

utpu

t (m

A /

mm

)

den(4)=930.7111den(3)=399.9695den(2)=3.7409num(1)=2298.7909

experimental ouput model output input

Figure 4.14 Identification results of Zone 4 ( input current from 1.6 ma to 2 ma)

Estimation results show that the coefficients of four transfer functions are almost the

same. At the same time, the damping coefficient, poles, and natural frequency of each transfer

function are compared in Table 4.2.

Table 4.2 Comparison of transfer function of each zone

Transfer function of each zone Real pole Complex pole nw ξ

1 3 2

2330H (s)s 3.2s 442s 931

=+ + +

-2.2 -0.54 + j21

-0.54 – j21

21 0.03

2 3 2

2341H (s)s 3.6s 452s 1012

=+ + +

-2.3 -0.67 + j21.2

-0.67 – j21.2

21.2 0.03

3 3 2

2364H (s)s 3.6s 454s 932

=+ + +

-2.1 -0.77 + j21.2

-0.77 – j21.2

21.2 0.04

4 3 2

2298H (s)s 3.7s 400s 931

=+ + +

-2 -0.68 + j19.9

-0.68 – j19.9

19.9 0.03

These comparisons also demonstrate that the estimation results are correct. These results

thus allow us to choose the function of zone 2 to represent the dynamic behavior at all its

working zones for small displacements. At the same time, identification results highlight a

good stability of poles of the model (Table 4.2). It is worth to note that for all zones we find one

real pole and two complex poles. The first one corresponds to the pneumatic part (Equation 4.1)

and the complex poles determine the poles of the mechanic part (Equation 4.2).



Since other two chambers have the same structure and the same control method,

parameters are estimated in the same way as those for the first chamber. Thus only the

determination of the nonlinear gains and the identification results are presented here omitting

the procedure here in order to lessen the burden. Figure 4.15 and 4.16 respectively present the

static nonlinearity of chamber 2 and chamber 3. They are both linearized through 4 linear zones

as chamber 1. Table 4.3 and Table 4.4 show the comparisons of the identification results for

each zone of chamber 2 and chamber 3. All four zones of each chamber give almost the same

estimation results as chamber 1 did. In the meanwhile, through the comparisons of the transfer

functions with chamber 1, it can be seen that the linear parts of three chamber systems have

almost the same dynamic behavior.

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 0

5

10

15

20

25 Determination of static nonlinearity of chamber2

Control current of servovalve (mA)

Dis

plac

emen

t of t

op-e

nd o

f ED

OR

A II

(mm

)

Zone 1 Zone 2

Zone 3

Zone 4

Figure 4.15 Determination of the static nonlinear gain of chamber 2

Table 4.3 Comparison of transfer function of each zone of chamber 2


1 3 2

3794H (s)s 4.6s 450s 1463

=+ + +

-3.3 -0.7 + j21

-0.7 – j21

21.1 0.03

2 3 2

3988H (s)s 5.6s 449s 1528

=+ + +

-3.5 -1 + j21

-1 – j21

21 0.05

3 3 2

3964H (s)s 6s 437s 1561

=+ + +

-3.6 -0.8 + j21.2

-0.8 – j21.2

21.2 0.06

4 3 2

3781H (s)s 5.9s 430s 1547

=+ + +

-3.6 -1.1 + j20.5

-1.1 – j20.5

20.5 0.05



0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 0

5

10

15

20

25 Determination of static nonlinearity of chamber

Control current of servovalve ( mA )

Dis

plac

emen

t of t

he to

p-en

d of

ED

OR

A II

Zone 1 Zone 2

Zone 3

Zone 4

Figure 4.16 Determination of the static nonlinear gain of chamber 3

Table 4.4 Comparison of the transfer function of each zone of chamber 3


1 3 2

3728H (s)s 5.3s 448s 1518

=+ + +

-3.4 -0.9 + j21

-0.9 – j21

21 0.04

2 3 2

3865H (s)s 6s 439s 1602

=+ + +

-3.7 -1.1 + j21

-1.1 – j21

21 0.05

3 3 2

3803H (s)s 6.5s 450s 1706

=+ + +

-3.9 -1.3 + j21

-1.3 – j21

21 0.06

4 3 2

2298H (s)s 6.1s 446s 1581

=+ + +

-3.6 -1.2 + j20.9

-1.2 – j20.9

20.9 0.06

4.3.4 Validation of identification results

After obtaining the models of the system, it is natural to determine if the model is an

adequate model for controller design. These are the problems of model validation. Model

validation is the heart of the identification problem, but there is no absolute procedure in

approaching it. The most often used method is to use validation experiment data.

It is a good choice to display the model properties in terms of quantities that have more

physical meaning than the parameters themselves, for example, Bode diagrams. It gives a sense

of the properties of the system that have been picked up by the model. If several models of

different characteristics give very similar Bode plots in the frequency range, we can be fairly



confident that these must reflect features of the true, unknown system. In this thesis, an

experimental Bode plot based on the experimental frequency response is chosen to validate the

identified model of zone 2.

10 -1 10 0 101

102

10 3 -270

-180

-90

0

Pha

se (d

eg)

-150

-100

-50

0

50 M

agni

tude

(dB

)

Frequency experimental resultsResults of model obtained from identification

Bode Diagram

Frequency (rad/sec)

Figure 4.17 Validation of identification result of one chamber of EDORA II (chamber 1)

The frequency response data are obtained from exciting the system with sinusoidal

inputs at different frequencies. The amplitude of sinusoidal inputs is the same as the one that

used for parameter estimation in section 4.3.2. The corresponding magnitude diagram and phase

diagram are then depicted based on this data. Figure 4.15 shows the Bode diagram of the

experiment and the diagram from the simulation of the identified model for one chamber. From

the magnitude and the phase diagram in figure 4.15, it can be seen that the two curves are

almost the same. So this validation experiment has proved that the identification results

demonstrated the physical property of the system.

4.4 Conclusions

In this chapter, the dynamics of EDORA II have been analyzed specifically in their

application from an experimental perspective. The total system (including electro-servovalve) is

decoupled into three independent subsystems. With the assumption that the small displacement

of top-end of EDORA II from the working point, each system is regarded as a linear element

and a static nonlinearity. A 3rd order system is then determined for the linear element of each

chamber. A direct identification approach using the output error model and the Levenberg



Marquardt (L-M) algorithm was used to estimate those system parameters. The validation of the

model is accomplished by comparing Bode diagram of the model with the Bode diagram

depicted from the frequency response data. From the comparison, it can be seen that the model

matches the experiment data well and can show the dynamic behavior of each actuator.

Chapter 5 Experimentation and test results

Gang CHEN 133

Thèse INSA de Lyon, LAI 2005

Chapter 5

Experimentation and test results



5

CHAPTER 5 EXPERIMENTATION AND TEST RESULTS .................................................................... 133

5.1 Introduction..................................................................................................................................... 135

5.2 Optical fiber sensors and their calibrations ..................................................................................... 135

5.3 Dynamic performance analysis of one chamber subsystem............................................................ 138

5.4 Controller design with disturbance of insertion .............................................................................. 139

5.4.1 Manipulation context and controller specifications ................................................................................. 139

5.4.2 Controller design using sensitivity function ............................................................................................ 140

5.4.3 Implementation of a lag compensator...................................................................................................... 141

5.4.4 Experiment setup ..................................................................................................................................... 142

5.4.5 Set point response with disturbance rejection.......................................................................................... 143

5.5 Exploration in a tube ....................................................................................................................... 145

5.6 Conclusion ...................................................................................................................................... 150



5.1 Introduction

In the previous chapters, we have built the experimental dynamic model and identified

its corresponding parameters for EDORA II. In this chapter, we will focus on the closed-loop

control of EDORA II. During the operation of colonoscopy, EDORA II needs to be kept as far

as possible from the colon wall. Furthermore, the manipulator’s position requires adjustment in

order for surgeons to have a good view of the colon. The EDORA II, which is designed to

replicate these functions of the steering by physician, will pay much more attention to avoiding

the difficult bends. So this chapter will address the close-loop control and testing in the colon-

like tube by using parameters obtained from the previous chapter.

5.2 Optical fiber sensors and their calibration

The miniBIRD 3-D sensor was used for validation of forward kinematics and dynamics

in the previous chapter. However, it can’t be used in order for EDORA II to explore the colon-

like tube. For this reason other position sensors are required to integrate into EDORA II.

Because of the flexibility of the optical fibers, of their small size and of their light resolution,

we have decided to use optical fibers [PRELLE 01] to measure the distance between the

EDORA II and the colon wall. Three sensors are borrowed from the laboratory of ROBERVAL,

Université Technologique of Compiègne.

As for the principle of the sensor, the light of optical fiber sensor is emitted from a cold

source of light, and is transferred by fiber. The light reflected by the mirror is then injected in

the reception fibers placed around the emission fiber, shown in figure 5.1.

Figure 5.1 Schema of the principle optical fiber sensor

The amount of reflected light detected is a function of the distance between the sensor

and the surface of the objet. The typical sensor response is shown in the figure 5.2. It is divided

into four working areas. The first one is the dead zone where the receiving fibers cannot collect

light because of the limited space between the emission and reception fibers. Area 2 is strongly

non linear and with a small range. Area 4 is non linear but useful for a millimetric range



measurement. Area 3 is the highest sensitivity zone. The range of area 3 is variable according to

the chosen linearity criterion – the smaller the criterion, the smaller the range. For example, in

the common use, a resolution of 1 nm on a 100 µm range can be achieved. It is always possible

to use the sensor in the area 4 to measure a linear displacement on a long range but the

resolution is less than the one in area 3 and it decreases along the range.

Figure 5.2 Fiber optic probe sensitivity [PRELLE 05]

As for our application, the goal is to avoid the contact of EDORA II with the colon wall,

so the measurement range of optical fiber sensors should be from more than 0 mm to about

20mm which is the distance between the manipulator and the colon wall. Thus the area 4 is a

good choice for our application. From figure 5.2, it is noticed that that there is a voltage peak

for low values of the distance. Since the objective is always to keep EDORA II far from the

colon wall, small values of distance don’t have any significance for our application. Thus, the

start point of the sensor is chosen from the point of the voltage peak for easier measurement.

By using a pipe emulating the intestinal walls, the relationship between the distance id

and the voltage iu (where i = 1,2,3 is the number of the optical fiber sensors )are obtained from

calibration as the following ( iu in V and id in mm):

1 21

40u3.2d 3

−=+ (5.1)

2 22

50u1.6d 2.2

−=+ (5.2)

3 23

38u1.7d 2.3

−=+ (5.3)



Figure 5.3 shows the model obtained for the third optical fiber sensor, which has a good

measurement precision for distances from 2 mm to 10 mm. As the diameter of the tube used for

the test is 35 mm and that of EDORA II is 17 mm, then the maximum value will be 18mm. So

this model is satisfactory for testing the performance of EDORA II in the tube.

0 2 4 6 8 10 12 -10

-9

-8

-7

-6

-5

-4

-3

-2

-1

0

Distance (mm)

Vol

tage

(mV

) Characteristics of optical fiber sensor 3

Model Measurement

Figure 5.3 Characteristics of the third optical fiber sensor

Three optical fibers can then be easily integrated into EDORA II. As has been shown in

chapter 3, EDORA II has 6 chambers at its circumference. Three chambers are used for the

power supply, and the other three chambers are reserved for optical fiber sensor placement.

However, for the preliminary experiments, we have just attached them on the surface of

EDORA II, shown in figure 5.4.

Figure 5.4 EDORA II with integration of optical fiber sensors



5.3 Dynamic performance analysis of one chamber subsystem

Before testing the performance of EDORA II in the colon-like tube, it is necessary to

design a controller to control the position of the top-end of the EDORA II in the tube. Thus the

dynamic performances of the EDORA II are firstly analyzed in this section based on a linear

transfer function and the controller design will be discussed in the following section. The model

for the linear part of the one chamber system of the EDORA II is obtained in the precedent

chapter and is represented by the transfer function 2H (s) of zone 2 for all the working area. It is

shown as:

2 3 2

2341G(s) H (s)s 3.6s 452s 1012

= =+ + +

(5.4)

Figure 5.5 shows the root locus of the open-loop system.

-80 -60 -40 -20 0 20 40 -80

-60

-40

-20

0

20

40

60

80

System: f2 Gain: 0.0577

Pole: -0.524 - 21.2i Damping: 0.0247

Overshoot (%): 92.5 Frequency (rad/sec): 21.2

System: f2 Gain: 0.0639 Pole: -0.508 + 21.2i Damping: 0.0239 Overshoot (%): 92.8 Frequency (rad/sec): 21.2

System: f2 Gain: 0.0498

Pole: -2.51 Damping: 1

Overshoot (%): 0 Frequency (rad/sec): 2.51

Root Locus

Real Axis

Imag

inar

y Ax

is

Figure 5.5 Root locus of open-loop system for one chamber of EDORA II

The poles of transfer function shown in figure 5.5 show that the system is stable but has

a very low damping ration, which will make the response of the system oscillatory. At the same

time, it can be seen that the system has a small variation of gain before it becomes unstable.

Figure 5.6 shows the step response of one chamber system with a gain of 0.1-0.4. With a

very small gain from 0.1 to 0.3, the system is stable but there is a very big steady-state error,

from 60 % to 80 %. But when the gain is augmented to 0.4, the system becomes oscillatory. Due

to the low damping ratio, the system shows some degrees of oscillation for all the gain from 0.1

to 0.4 and thus generates a long adjustment time. Therefore, using only proportional control

methods is not sufficient for the EDORA II to adjust its position relating to the environment.

Thus, a controller should be conceived to insure that the system has a good margin of stability,



accuracy and robustness with respect to modeling errors. Thus section 5.4 will be concerned

with the requirement of the controller and its design.

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 0

0.2

0.4

0.6

0.8

1

Time (s)

Dis

plac

emen

t of t

op-e

nd (m

m)

Simulation of step response of one chamber without controller Reference input G=0.4 G =0.3 G = 0.2 G = 0.1

Figure 5.6 Step response of one chamber of EDORA II with different gains

5.4 Controller design with disturbance of insertion

As analyzed in 5.3, the dynamic response of the system presented big steady-state errors

and a weak stability margin. So it’s necessary to design a controller to improve the dynamic

performance to meet the desired specifications. In addition, the diagnostic procedure is not a

normal manipulation as the one used in industry, but a special manipulation of minimal contact

with the colon tissue. Our automatic manipulator EDORA II, which attempts to replicate the

function of the steering by the physician, will pay much more attention to avoiding the difficult

bends.

5.4.1 Manipulation context and controller specifications

Our resolution to improve the performance of a traditional colonoscopy is to replace the

distal end of traditional colonoscopy by designing a new automatic manipulator-EDORA II

while the progression of the colonoscope is kept for the endoscopist. Then, the bendable

manipulator will automatically find the advance direction by controlling the movement of the

EDORA II. During the process of insertion, as described in chapter 1, the colonoscope is



advanced by a variety of “in-and-out” maneuver action to “accordion” the colon [KASSIM 03].

So these movements of the colonoscope exert much disturbance for the control of the position

of the robotic tip. In addition to this, the casual motion due to breathing movements will also

affect the instrument’s position in the colon and the corresponding measurement results.

As far as these problems are concerned, the objective of designing a controller is to let

the manipulator not touch the colon wall under the circumstance of strong disturbance.

However, the contact between the instrument and the colon may take place due to the

disturbance discussed previously. This aspect is not desirable because strong contact forces can

become apparent if the stiffness is too great, which can bring more pain to patients. In the event

of contact, positioning accuracy will no longer be the only primary concern and the compliance

of the instrument should be treated to lessen harm to the colon tissue.

5.4.2 Controller design using sensitivity function

To satisfy these specifications: disturbance rejection and some kind of compliance, a

position-based manipulation control strategy is needed. PI controller is a good choice because it

can be readily implemented and has zero steady-state errors. However, the stiffness will become

infinitive when there is no steady-state errors [PRELLE 01]. This case is not allowed for our

operation conditions due to the consideration of safety. So a lag compensator is chosen as a

compromise between the performance and compliance. Let the loop transfer function be L(s) =

D(s)G(s) where D(s) is the transfer function of the controller to be designed, the maximum

sensitivity is then given by Ms = Max|S(jw)|. As is shown in [FRANKLIN 94], the quantity Ms

is the inverse of the shortest distance from the Nyquist plot of the loop transfer function to the

critical point (-1, j0). Typical values of Ms are in the range of 1.2 –2.0 [ASTROM 98]. If the

value of maximum sensitivity is given, the gain margin (GM) and phase margin (PM) can be

estimated in a conservative way [FRANKLIN 94], as showed in Equation (5.5) and (5.6).

1GM = 20log1⎛ ⎞⎜ ⎟− α⎝ ⎠

(5.5)

And :

PM = 2arcsin( / 2)α (5.6)

where 1/ Msα = and α <1.



5.4.3 Implementation of a lag compensator

In our case, we take Ms = 1.2 with the least sensitivity to the modeling errors. The

corresponding gain margin and phase margin for the transfer function (equation 5.4 ) in zone 2

are obtained as 11 dB and 64 degree by using Equation (5.5) and (5.6). With the phase margin

as described in the specification of the lag compensation, the lag compensator is given by:

0.13s 1D(s) 44s 1

+⎛ ⎞= ⎜ ⎟+⎝ ⎠ (5.7)

-1 0 1 2 3 4 5 6 7 8 0

1

2

3

4

5

6Comparison of the step response for lag controller

Time ( s )

Ste

p in

put a

nd it

s re

pons

e (m

m)

Experimental Expected Simulation

Figure 5.7 Comparison of step response between simulation and the experiment

After the lag controller is designed, it has been implemented with hardware for real

experiments. An experiment is first done in the zone 2 where the dynamic model was identified

(chapter 4.3.3). In order to be in accordance with the condition where the model is obtained, a

step of position of 6mm, which will fall into the zone 2, is applied for one chamber system.

Figure 5.7 is the comparison of step response between the experimental result and the

simulation of the model. The dash-doted line is the simulation result and the solid line is the

experimental result. It can be seen that experimental result is well in accordance with the

simulation result. This fact also proved that the dynamic model obtained in chapter 4 gives a

good modeling of the behavior into the zone 2 (figure 4.4). As it has been explained in chapter

4, since the system is a nonlinear system, other experiments with different conditions are carried

out to check the robustness of this controller within all the working zones of EDORA II.

Experimental results and their comparison of 4 different cases are shown in figure 5.8. Figure

5.8 shows that one chamber of EDORA II has the same dynamic response for the entire working

zone, except that there is a difference for the steady-state value. The reason for this result is



explained as due to the fact that the EDORA II is a nonlinear system with different static gain

when it works in the different zones (Chapter 4.1.2). Therefore, under the assumption of small

displacements of top-end of EDORA II, this controller can work well within the entire working

zone of EDORA II and it ensures the availability of the test of EDORA II in the tube.

-1 0 1 2 3 4 5 6 7 8 -1

0

1

2

3

4

5

6

7

Time (s)

Pos

ition

of t

op-e

nd o

f ED

OR

A II

(mm

)

Step response of lag controller from different working zone

Zone 2expected valueSimulationZone 1Zone 3Zone 4

Figure 5.8 Comparison of step response between simulation and the experiment

5.4.4 Experiment setup

Since the insertion disturbance of the colonoscope is an important factor to test the

performances of EDORA II, a platform is designed and built to emulate the insertion process of

a colonoscope in the colon. The platform is shown in figure 5.9, which can manually move in

two directions (X, Y).

The bottom of EDORA II is fixed on that platform, EDORA II can thus move in the

same way as does the platform. A tube with the diameter of 35mm is placed in a circle

emulating the colon. Three optical fiber sensors are used for measuring the distance between

EDORA II and the wall of the tube. Figure 5.10 shows the simplified block diagram for

feedback control of one chamber of EDORA II.



Figure 5.9 Top view of the experiment setup

5.4.5 Set point response with disturbance rejection

Figure 5.10 shows the control structure for the whole system. The path planner is used to

determine the reference point of three chambers. The first experiment is done to verify the

controller performance for one single chamber in a single direction. The platform for emulating

the insertion movement is moved in the X direction between 2 mm to 26 mm, which is the

disturbance for the reference input.

Path Planner

Controller 1

-Servovalve + Chamber 3+ Controller 3

-Servovalve + Chamber 2Controller 2+

-Servovalve + Chamber 1+

Position In the plate

Optical fiber sensor 1



Figure 5.10 the structure of the whole control system

X

Y

The base



Figure 5.11 shows the measurements of the position of the top-end with respect to the

tube, the reference position. The dashed line is the movement of the base along the axis X and

the solid line represents the real position of the top-end of EDORA II with respect to the tube. It

is clear that the system has drastically rejected the disturbance brought from the movement of

the platform. This result shows that the designed controller has a good performance record of

keeping the top-end of EDORA II to stay near the expected position while there exists a

continuous disturbance.

0 1 2 3 4 5 6 7 8 9 10 -10

-5

0

5

10

15

20

25

30

35

40

45

Time ( s )

Pos

ition

of t

op-e

nd in

the

sim

ulat

or (

mm

)

Disturbance rejection of the controllerthe movement of Xposition of top-end of EDORA II desired position The Wall of the tube

Figure 5.11 The performance of disturbance rejection of the lag compensator

The second experiment is to test if three controllers can work well at the same time for

three chambers of the EDORA II in the entire plane. Thus the platform will move stochastically

in X and Y directions in order to emulate the movement of a colonoscope in the colon. In this

case, the expected position of the top-end of the EDORA II is chosen as the center of the tube

far from the wall of the tube and the reference values for three controllers are then 17.5mm.

Measurements of three sensors are shown in figure 5.12. The values of the measurements of

three sensors are around 17.5 mm with a minimal value of 11mm and a maximal value of

23mm. That is to say, the top-end of the EDORA II can stay around the center of tube under the

disturbance. This result supported the hypothesis that three controllers can work well at the

same time and have good disturbance rejection ability.



0 1 2 3 4 5 6 7 8 9 10 -5

0

5

10

15

20

25

30

35

40 Experimental results for three controllers in the same time

Time (s)

Thre

e m

easu

rem

ents

of d

1, d

2, d

3 (m

m)

Distance 1Distance 2Distance 3The wall of the tube

Figure 5.12 Experimental result of three controller together with the insertion disturbance

5.5 Exploration in a tube

Figure 5.13 Test tube with a bend of 100°

For the validation of the conception of EDORA II, the most effective test is that if

EDORA II can easily cross the tube with a very big bend. So a suitable experiment is necessary

to test its movements in the colon-like tube. In our preliminary experiment, we use a transparent



tube with a 100° bend shown in figure 5.13. The diameter of the tube is 26 mm which is less

than the average diameter of the colon (50mm) and its length is 50 cm.

Figure 5.14 EDORA II with a covering tube for easier insertion

For the purpose of easier insertion, a soft tube 50 cm in length is used to put the entire

tube inside it, as shown in figure 5.14. During the experiment, EDORA II is inserted into the

test tube manually with the help of this covering tube. The designed controllers of EDOAR II

will adjust the position of EDORA II in the tube in order to cross the big bend minimizing the

touch with the inner wall of the tube. As it has been described, small displacement of top-end of

EDORA II is assumed to obtain the dynamic model. This assumption is suitable to the way that

EDORA II traverses the big bend. EDORA II accumulates a great deformation in accord with

the tube bend by small displacement step by step during its progression in the tube. So it is

assumed that the top-end end of EDORA II is always orthogonal to the axis of the tube. Thus

the optical fiber sensors can work the same way as they are calibrated. The schema in figure

5.15 shows the distances from three optical fibers d1, d2 and d3 and the position of the top-end

of EDORA II in the tube (O' is the center point of top-end of EDORA II).

Figure 5.15 Schema of distances d1, d2 and d3 and the position of top-end of EDORA II in the tube.

d1

d2

d3

x

y

O'

Inner wall of the tube

Top-end of EDORA II



During this process, EDORA II is inserted manually into the test tube with a velocity

about 4 cm/sec. A simple path planing algorithm is used and easily implemented to get the

reference point of three controllers: the center of the tube. At each place, there is always one

distance from three sensors that will be shortest. When one distance becomes too small beyond

the limit, the controller will command EDORA II to move to the opposite direction in order to

avoid touching of the wall of the tube.

Figure 5.16 shows different bending angles of EDORA II at the two special positions

when EDORA II crosses a tube of 100°. Figure 5.16a shows the position of EDORA II during

the start stage of the crossing. It can be seen that EDORA II bend by very few degrees in the

tube. Then when EDORA II reaches the position with the big bend, EDORA II bends itself in

accordance with the bend of the tube so that it can cross this bend, shown in figure 5.16b. From

this experiment, the assumption proved to be correct that the EDORA II crosses the big bend

through accumulating small bending movements along the path of the tube.

(a) (b)

Figure 5.16 Evolution of bending angle of EDORA II during the cross of a tube with 100°

The measurements of three optical fiber sensors d1, d2 and d3 allow us to see the

evolution of the position of the top-end of EDORA II with respect to the wall of the tube

represented in figure 5.17. Three distances varied with the position in the tube, but these

distances are never less than 0.8 mm. The reaction of EDORA II under the influence of the

controllers thus fulfilled our expectations.



0 5 10 15 20 25 30 35 40 0

1

2

3

4

5

6

7

8

9

Length of the tube (cm)

Mea

sure

men

ts o

f thr

ee s

enso

rs (m

m)

Evolution of measurements of three sensors

Sensor 1Sensor 2Sensor 3

Figure 5.17 Evolution of the measurements of three sensors

For a better representation and visualization, the position limit of the top-end of EDORA

II in the tube along the progression of 40 cm is drawn in XOY plan, shown in figure 5.18.

30

210

60

240

90

270

120

300

150

330

180 0X

Y

8mm

8 m

m

The wall the tube (Inner diameter 26mm)

Envelope of the position limit of EDAR II in the tube

Top-end of EDORA II in the middle of thu tube (diameter of 17mm)

Figure 5.18 Extreme position of top-end of EDORA II in the tube.



0 5 10 15 20 25 30 35 40 -25

-20

-15

-10

-5

0

5

10

15

20

25

Length of the tube (cm )

Dia

met

er o

f the

tube

(mm

)

Positon of EDORA II in the linear tube ((X,Z) plan)

The wall of the tube

8.5mm

8.5mm

Figure 5.19 Position of EDORA II on the (X, Z) plan

0 5 10 15 20 25 30 35 40 -25

-20

-15

-10

-5

0

5

10

15

20

25

Length of the tube (cm)

Dia

met

er o

f the

tube

(mm

)

Positon of EDORA II in the linear tube ((Y,Z) plan)

The wall of the tube

8.5mm

8.5mm

Figure 5.20 Position of EDORA II on the (Y, Z) plan

We can also represent the evolution of the position of the contours of the top end of

EDORA II along the entire length of the tube. Figure 5.19 and 5.20 demonstrate the projection

of these positions on the (X, Z) plan and (Y,Z) plan which are all bounded with the tube.

All of these figures demonstrate that three controllers for three chamber systems of

EDORA II (diameter of 26 mm) make its top-end keep a constant distance of 0.8mm from the

wall. Thus, experimental results have proved to meet the requirements in order to control the



position with respect to the wall of the tube and also proved the capability of the EDORA II to

cross a tube with a big bend of 100° without touching the wall.

5.6 Conclusion

In this chapter, we have shown that the feasibility of our design of EDORA II fulfils our

expectations. Firstly, the optical fiber sensors are chosen for measuring the distance between

EDORA II and the test tube. The integration of optical fiber sensors into EDORA II allows us to

test the performances of this micro-robot when it’s guided through a colon-like tube

automatically. Then, its physical characteristics were calibrated and the static model was built

for feedback control. After that, the dynamic performances of closed-loop system of EDORA II

are analyzed by applying a step position input. Experimental results show that there are many

steady-state errors and a small stability margin. In order to improve the dynamic performance, a

lag controller that considers the manipulation disturbance is designed. The validation

experiments are carried out on a simulation platform which can move in X and Y directions.

This platform is designed to emulate the insertion movement of the colonoscope in the colon.

Two potentiometers are installed to read the distances along the axe X and Y. Results from one

chamber system moving only in one direction and three chamber systems moving in a plane

together show that this controller has good disturbance rejection ability. By using the same

controllers, a test experiment was done in a tube with a bend of 100°. A simple path planing

algorithm is used to generate the desired position for three controllers: the center of the tube. At

each place, there is always one distance from three sensors that will be smallest. When one

distance becomes too small beyond the limit, the controller will command the EDORA II to

move in the opposite direction in order to avoid touching the wall of the tube. So every time,

there is only one controller that will react according to the priority. Experimental results show

that the EDORA II can easily cross a bend of 100° without touching the wall of the tube. At the

same time, it also verified the assumption that the EDORA II accumulates a great deformation

in accordance with the great bend by small step by step displacement with its progression in the

tube. More precisely, it justified the validity of the EDORA II design and also the feasibility to

improve the performances of the traditional colonoscopy in view of the purpose of this

dissertation.


Conclusions and Perspectives :

In this dissertation, the work deals with design, modeling, control and test of a micro-

robotic manipulator (EDORA II) for colonoscopy in accordance with Minimally Invasive

Surgery.

In the first chapter, after the analysis of the problems of conventional colonoscopy, the

principle drawbacks of a conventional colonoscopy are summarized using two aspects:

complexity of the operation for physicians and the pain induced to the patient. The related work

on improving the conventional colonoscopy procedure by using robotics has been studied and

analyzed.

• The complete replacement of conventional colonoscope by designing a fully autonomous robot

which propels itself in the colon. The most often used mechanism is the inch-worm movement

which uses the clamper to cling to the colon wall and then stretches itself by using pneumatic

bellows.

• The replacement of the bending distal end of the colonoscope by designing an active bendable

robotic tip while the insertion of procedure is kept for the physicians.

In view of the low efficiency and weak reliability of self-propulsion and after some

discussion with physicians, we have decided to design a robotic manipulator which can

automatically guide the introduction of the colonoscope. Then in the second chapter, the

continuum style robot, which does not have any form of mechanical linkage, is first introduced

as it is quite suitable for the environment of colonoscopy that requires a high degree of

flexibility and maneuverability. The technical requirements of EDORA II concerning the size

and the actuation approach have been put forward tailed to the colonoscopy. Then, the design of

a new continuum robot EDORA II was presented. It does not have any form of mechanical

linkage joints, which can produce sophisticated movements and can achieve configurations that

would require a conventional style robot with many more actuators. EDORA II is made of

silicone rubber with three chambers distributed at the circumference of its body. It has an


exterior diameter of 17 mm and a length of about 100 mm. Its weight is about 20g, which is

very suitable for the explorations of the colon. Three pneumatic servovalves are utilized to

control the pressure of each chamber independently to get the expected motion of distal end of

EDORA II. When the pressure is increased, the actuator elongates and, in the case of uneven

pressure among the three chambers, it can bend at any degree. The most promising fact is that

EDORA II can bend up 120 degrees when the pressure is augmented to 2 bars, which proves to

be important to traverse big bends of the colon.

In order to facilitate the representation of the motion of top-end of EDORA II, a new

kinematic model is developed. Unlike conventional manipulators which use link lengths and

joints as a basis for their kinematic model, three geometric parameters were chosen to represent

the position/orientation of top-end of EDORA II with the assumption that the deflected shape is

an arc of a circle and the effects are ignored. They are L, the virtual length of the center line of

the robotic manipulator; α , the bending angle in the bending plane and φ , the orientation of the

bending plane. Thus the forward kinematic model of EDORA II has been established relating

these three parameters to the length of three chambers. Unlike other works on the linearity of

the actuator, the nonlinear models of each chamber were obtained through experiments. Thus,

the kinematics relating to three system parameters to three input pressures were then

determined. Based on the forward kinematics analysis, the velocity kinematics are then studied

from two cases: non-redundant and redundant. In the case of redundant manipulation with

relation to the chosen variables: bending angle and orientation angle in the task space, the

inverse velocity kinematics is studied for kinematic control. Experiments have been done to

validate the bending angle and orientation of EDORA II respectively. To check if there is any

mutual interaction among each chamber, sinuous signals of pressure with 120° delay among

each chamber with a definitive velocity are employed to make EDORA II turn around its

vertical axis. Comparative results between the experiment and the simulation show that there is

some mutual interaction among each chamber. Thus a new correction parameter is chosen to

represent this effect and its value is determined through an optimization.

Then in chapter 4, the dynamics of EDORA II specific to the application has been

analyzed from an experimental perspective. The total system (including electro-servovalve) is

decoupled into three independent subsystems. With the assumption that the small displacement

of top-end of EDORA II from the working point, each system is regarded as a linear element

and a static nonlinearity. A 3rd order system is then determined for the linear element of each

chamber. A direct identification approach using the output error model and the Levenberg


Marquardt (L-M) algorithm was used to estimate those system parameters. The validation of the

model is accomplished by comparing the Bode diagram of the model with the Bode diagram

depicted from the frequency response data. From the comparison, it can be seen that model

matches the experiment data well and can show the dynamic behavior of each actuator.

The final chapter dealt with controller design and the feasibility test in the colon-like

tube. Firstly, optical fiber sensors are chosen for measuring the distance between EDORA II and

the wall of a test tube. The dynamic performance of closed-loop system of EDORA II is

analyzed by applying a step position input. Experimental results show that there is much steady-

state error and small stability margin. A lag controller is then designed in order to improve the

dynamic performance and to remove the disturbance brought about during the insertion. For the

validation of the controller, a simulation platform which can move in X and Y directions has

been constructed. Its movements emulate the insertion action of colonoscope in the colon. By

using one controller and three controllers for three subsystems in the same time, both

experiments show that the controller has good performances of disturbances rejection. Then by

using the same controllers, the test experiment is carried out in a tube with a bend of 100°. It

shows that EDORA II can easily cross a great bend of 100° without touching the wall of the

tube. Furthermore, it justified that the design of EDORA II is feasible to improve the

performances of traditional colonoscopy.

The research presented in this dissertation dealt with the work from the concept of

EDORA II to its final test in a colon-like tube. Both the design of EDORA II, its kinematic and

dynamic models give good results. In addition, the test in the tube proves that EDORA II can

easily cross great bends of 100° without touching the wall of the colon. However, there are still

many improvements that can be made from the following aspects:

1. Design of EDORA II:

In order to further miniaturize our prototype and to obtain more flexion, the research on optimal

design of the manipulator will continue concerning with the form of three rooms (Now the

section of the room is a form of a circle). Moreover, with the efforts to modify the Young

modulus of silicone by adding various proportions of matter called silica, the radial expansion

can be avoided completely. For the actuation of each chamber, actuation using a hydraulic-

driven system is an alternative which is much safer than pneumatic driven system for our

application. The preliminary experiment shows that EDORA II driven by hydraulic energy can

bend much more with the same pressure than when driven by air pressure.

2. Kinematic model


The model of EDORA II was obtained with the assumption that the deflected shape is an arc of

a circle. To precisely represent the position of top-end of EDORA II, the more complicated

shape should be considered. A series of circular arcs can be used to represent the geometric

shape of EDORA II, as shown in figure 6.1. Thus, the generalized kinematic model needs to be

developed considering when the deflected angle exceeds the constraint of 90° as is done in this

dissertation.

Figure 6.1

3. Application related problems

EDORA II has been tested in a colon-like tube with a bend of 100° with a simple path planning

strategy. In order for EDORA II to be guided more precisely, however, more advanced path

planning strategies need to be conceived. Furthermore, test experiments need to be done in a

more complicated tube with more bends. In the long term, tests in vivo need to be considered in

order to verify its performance.

References


References

[AICARDI 95] AICARDI M., CANNATA A., CASALINO G., Stability and robustness analysis of a two layered hierarchical architecture for the closed loop control of robots in the operational space, IEEE Conference on Robotics and Automation, Nagoya, 1995, pp. 2771-2778.

[ANDERSON 67]ANDERSON V.C., HORN R.C., Tensor Arm Manipulator Design. ASME paper 67-DE-57, 1967, pp. 1-12,

[ANGELES 88] ANGELES J., Isotropy criteria in the kinematic design and control of redundant manipulators, Preprints of the NATO Advanced Research Workshop on Robots with redundancy: Design, Sensing and Control, Italy, 1988.

[ANTHIERENS 99]ANTHIERENS C., Conception d'un Microrobot à actionneur asservi électropneumatiquement pour l'inspection intratubulaire (en ligne). Thèse LAI. Lyon : INSA de Lyon, 1999, 145p. http://csidoc.insa-lyon.fr/these/1999/anthierens/index.html (consulté le 15 janvier 2005)

[AME 05] Colorectal Cancer Facts & Figures: Special Edition 2005, American Cancer Socity. http://www.cancer.org/docroot/STT/stt_0.asp (consulté le 15 janvier 2005)

[AOKI 02] AOKI T., OHNO H., HIROSE S., Design of Slim Slime Robot II (SSR-II) with Bridel Bellows, Proceddings of the 2002 IEEE/RSJ International Conference on Intelligent Robots and Systems, Lausanne, Switzerland, October 2002, pp. 835-840.

[ARAMAKI 95] ARAMAKI S., KANEKO S., ARAI K., TAKAHASHI Y., ADACHI H., YANAGISAWA K., Tube Type Micro Manipulator Using Shape Memory Alloy (SMA), 6th International Symposium on Micro Machine and Human Science, Nagoya, October 4-6, 1995, pp. 115-120.

http://csidoc.insa-lyon.fr/these/1999/anthierens/

http://csidoc.insa-lyon.fr/these/1999/anthierens/

http://www.cancer.org/docroot/STT/stt_0.asp

References


[ARRICHIELLO 98]ARRICHIELLO V., BARTOLINI G., COCCOLI M., “Modeling anc control of New Elements of the Amadeus Gripper Designed for Fast Manipulative Tasks”, IEEE Ocean, Nice, France, vol.2, 1998, pp, 708-712.

[ASARI 00] ASARI V. K., KUMAR S., A fully autonomous microrobotic endoscopy, Journal of Intelligent and Robotic Systems. 28, 2000, pp.325-341.

[ASTROM 84] ASTROM K.J., HAGANDER P., STERNB J., Zeros of sampled systems. Automatica, vol. 20 (1), 1984, pp. 31-38.

[ASTROM 98] ASTROM K. J., PANAGOPOULOS H., HAGGLUND T., “Design of PI controllers based on non-convex optimization,” Automatica, vol. 34 (5), 1998, pp. 585-601.

[BAILLY 04a] BAILLY Y., Modelisation et commande d’un micro-robot hybride-Application a la pose d’endoprotheses aortiques en chirurgie mini-invasive, Thèse de LIIA: L’UNVERSITE PARIS XII- Val de Marne, 2004, 160p.

[BAILLY 04b] BAILLY Y., CHAUVIN A., AMIRAT Y., Control of a high dexterity micro-robot based catheter for aortic aneurysm treatment, IEEE International Conference on Robotics Automation and Mechatronics, Singapore, December 2004, pp.65-70.

[BASTOGNE 01]BASTOGNE T., GARNIER H., SIBILLE P. A PMF-based subspace method for continuous-time model identification. Application to a multivariable winding process. International Journal of Control, 74 (2), 2001, pp.118-132.

[BONNANS 97] BONNANS J. F., GILBERT J.C., LEMARECHAL C., et SAGASTIZABAL C., Optimisation Numérique: Aspects théoriques et pratiques, Paris: Springer, 1997

[BURDICK 94] BURDICK, J., GRUNDFEST, W., SLATKIN, B.A., Robotic Endoscopy, US patent 5,337,732,1994.

[CARROZZA 96] CARROZZA M.C., LENCIONI L., MAGNANI B., DARIO P., REYNAERTS D, TRIVELLA M.G., PIETRABISSA A., A microrobot for colonoscopy. In Proceedings of the Seventh International Symposium on Micro Machine and Human Science (MHS ’96), Nagoya, Japan, October 2–4, 1996, pp. 223–228.

[CARROZZA 97]CARROZZA M.C., LENCIONI L., MAGNANI B., DARIO P., The development of a microrobot system for colonoscopy. In: Troccaz J, Grimson

References


E, Mosges R. (eds): CVRMed-MRCAS ’97, Lecture Notes in Computer Science 1025, Berlin: Springer,1997, pp. 779–788.

[CHEN 03] CHEN G., THOMANN G., BETEMPS M., REDARCE T., Identification of the flexible actuator of a colonoscope, IROS2003, Las Vegas, USA, October 27-31, 2003, pp. 3355-3360.

[CHEN 04] CHEN G., THOMANN G., PHAM M., T., BETEMPS M., REDARCE T., Modeling and Control of a Colonoscopic Tip under the Disturbance of the Insertion of Colonoscope, IROS2004, Sendaï, Japan, September 28 – October 2, 2004, pp. 3315-3320.

[CHEN 05] CHEN G., PHAM M.T., REDARCE T., Design and Modeling of a Micro-Robotic Manipulator for Colonoscopy, 6th International workshop on Research and Education in Mechatronics, annecy, France, 2005, pp.109-114.

[CHIRIKJIAN 92]CHIRIKJIAN G.S., Theory and Applications of Hyper-Redundant Robotic Mechanisms,. Ph.D. Thesis Dept. of Applied Mechanics, California Institute of Technology, 1992.

[CHIRIKJIAN 93]CHIRIKJIAN G.S., A General Numerical Method for Hyper-Redundant Manipulator Inverse Kinematics, IEEE International Conference on Robotics and Automation, May 2-6, Atalanta pp. 107-112.

[CHIRIKJIAN 94]CHIRIKJIAN G.S., BURDICK J.W., A Model Approach to Hyper-Redundant Manipulator Kinematics,. IEEE International Conference on Robotics and Automation, May 8-13, San Diego, USA, 1994, pp. 343-354.

[CHIRIKJIAN 95]CHIRIKJIAN G.S., BURDICK J.W., Kinematically Optimal Hyper-Redundant Manipulator Configurations,. IEEE International Conference on Robotics and Automation, May 21-27, Nagoya, Japan, 1995, pp. 794-780.

[CHIU 88] CHIU S.L., Task compatibility of manipulator postures, International Journal of Robot. Res. 7(5), 1988, pp.13-21.

[CIESLAK 99 ] CIESLAK R., MORECKI A., Elephant Trunk Type Elastic Manipulator - A Tool for Bulk and Liquid Materials Transportation. Robotica, Vol. 17, 1999, pp. 11-16.

[CRAIG 89] CRAIG J. J., Introduction to Robotics: mechanics and control, 2nd ed. Reading, Mass.: Addison-Wesley, 1989.

References


[DARIO 97] DARIO P, CARROZZA M.C., LENCIONI L., MAGNANI B., D’ATTANASIO S., A micro robotic system for colonoscopy. Proceedings of the 1997 IEEE International Conference on Robotics and Automation, Albuquerque, USA, April 20–25, 1997, pp. 1567–1572.

[DARIO 99] DARIO P., CARROZZA M.C., and PIETRABISSA A., Development and in vitro tests of a miniature robotic system for computer-assisted colonoscopy, Jounal of Computer Aided Surgery, vol. 4, 1999, pp. 4-14.

[DARIO 03] DARIO P., HANNAFORD B., and MENCIASSI A., Smart Sugical Tools ans Augmenting Devices, IEEE transactions on Robotics and Automation, vol. 19 No. 5, 2003, pp. 782-792.

[DAVIS 91] DAVIES J. B. C., Elephants Trunks an Unforgettable Alternative to Rigid Mechanics, Industrial Robot, vol.28, 1991, pp. 29-30.

[DAVIES 96] DAVIES J.B.C., A Flexible Motion generator, Ph.D thesis, Heriot-Watt University, Edinburgh, 1996, 173p.

[DAVIES 00] DAVIES B., A review of robotics in surgery, Proceeding of Institute of Mechanical Engineering [H], vol. 214, 2000, pp. 129-140.

[FRANKLIN 94] FRANKLIN G. F., POWELL J. D., EMAMI-NAEINI A., “Feedback Control of Dynamic Systems,” 3th Edition, Reading, Mass.: Addison-Wesley, 1994, pp. 420-427.

[FRAZER 79] FRAZER, R.E., Apparatus for Endoscopic Examination, United States Patent, Patent Number: 4,176,662,1979.

[FUKUDA 89] FUKUDA T., HOSOKAI H., UEMURA M., Rubber Gas Actuator Driven by Hidrogen Storage Alloy for In-Pipe Inspection Mobile Robot with Flexible Structure, Proceeding of the IEEE International Conference on Robotics and Automation, Scottsdale, Arizona, USA, 1989, pp. 1847-1852.

[FUKUDA 94] FUKUDA T., GUO S., KOSUGE K., ARAI F., NEGORO M., and NAKABAYASHI K., Micro active catheter system with multi degrees of freedom. Proceedings of the IEEE International Conference on Robotics and Automation, pp. 2290- 2295,1994

[GARNIER 00] GARNIER H., MENSLER M., The CONTSID toolbox : a Matlab toolbox for CONtinuous-time System Identification, 12th IFAC Symposium on System Identification, Santa Barbara, 2000.

References


[GIVEN] Given Imaging, Expanding the scope of GI – M2A, [online], Available: http://www.givenimaging.com (consulté le 20 mars 2005)

[GONG 00] GONG F., SWAIN C.P., and MILLS T.N., wireless endoscopy. Gastrointestinal endoscopy, vol. 51, No. 6, 2000

[GRAVAGNE 00a]GRAVAGNE I., WALKER I.D., On the Kinematics of Remotely-Actuated Continuum Robots,. IEEE Conf. on Robotics and Automation, San Francisco, USA, April 24-28, 2000, pp. 2544-2550.

[GRAVAGNE 00b]GRAVAGNE I., WALKER I.D., Kinematic Transformations for Remotely-Actuated Planar Continuum,. IEEE Conf. on Robotics and Automation, San Francisco, USA, April 24-28, 2000, pp. 19-26.

[GRAVAGNE 00c]GRAVAGNE I., WALKER I.D., Kinematics for Constrained Continuum Robots Using Wavelet Decomposition, Robotics 2000, Proceedings of the 4th Int. Conf. and Expo./Demo. on Robotics for Challenging Situations and Environments, February 27-March 2, 2000, Albuquerque, USA, pp. 292-298.

[GRAVAGNE 02]GRAVAGNE I., WALKER I.D., Manipulator, force, and compliance analysis for planar continuum manipulators, IEEE Transactions on Robotics and Automation, 18(3),2002, pp.263-273.

[HANNAN 01] HANNAN M.W, Walker I.D., Analysis and Experiments with an Elephant’s Trunk Robot. International Journal of the Robotics Society of Japan, Vol. 15, No. 8, 2001, pp. 847-858.

[HANNAN 03] HANNAN M., WALKER I., Kinematics and the implementation of an elephant’s trunk manipulator and other continuum style robots, Journal of Robotic Systems, 20(2), 2003, pp.45-63.

[HEMAMI 94] HEMAMI A., Design of Light Weight Flexible Robot Arm, Robots & conference Proceedings, Detroit, June 4-7, 1984, pp. 16-23.

[HIROSE 93] HIROSE S., CAVE P., and GOULDEN C., Biologically inspired robots: snake-like locomotion and manipulators, Oxford, U.K. Oxford Univ. Press, 1993.

[HOLLERBACH 86]HOLLERBACH J.M., SUH K.C., Redundancy Resolution of Manipulator through Torque Optimization, A.I. Memo 882, Massachusetts Institute of Technology, 1986.

http://www.givenimaging.com/

References


[IDDAN 97] IDDAN G. J., STURLESI D., In-Vivo Video Camera, United States Patent, Patent Number: 5,604.531, 1997

[IMMGEA 95] IMMEGA G., ANTONELLI K., The KSI Tentacle Manipulator,. IEEE Conf. on Robotics and Automation, May 21-27, Nagoya, Japan, 1995, pp. 3149-3154.

[IKUTA 88] IKUTA K., TSUKAMOTO M., and HIROSE S., Shape memory alloy servo actuator system with electrical resistance feedback and application for active endoscope, IEEE Conference on Robotics and Automation, Philadelphia, Pennsylvania, April 24-29, 1988, pp. 427-430.

[ISERMANN 93] ISERMANN R., Fault diagnosis of machines via parameters estimation and knowledge processing-turorial paper, Journal of Automatica, Vol. 29, No. 4, 1993, pp. 815-835.

[IVANESCU 95] IVANESCU M., STOIAN V., A Variable Structure Controller for a Tentacle Manipulator, Proceddings of IEEE/RSJ International Conference on Robots and Automation, Nagoya, Japan, 1995, pp. 3155- 3160.

[JACKSON] Jackson Gastroenterology, http://www.gicare.com/pated/epdgs19.htm (consulté le 10 Janvier 2005)

[KALLIO 98] KALLIO P., LIND M., ZHOU Q., KOIVO H.N., A 3DOF Piezohydraulic Parallel Manipulator, Proceddings of IEEE/RSJ International Conference on Robots and Automation, leuven, Belgium, 1998, pp. 1823- 1828.

[KASSIM 03] KASSIM I., NG W.S., FENG G., PHEE S. J., Review of locomotion techniques for robotic colonoscopy, Proceeding of the 2003 International Conference on Robotics and Automation, Taiwan, 2003, pp. 1086-1091.

[KHATIB 88] KHATIB O., A unified approach for motion and force control of robot manipulators: the operational space approach, IEEE Journal of Robotics and Automation, vol3, 1988, 43-53.

[KIER 85] KIER W., SMITH K., Tongues, Tentacles and Trunks ; the Biomechanics of Movement in Muscular Hydrostats, Zoological Journal of the Linnean Society, vol, 83, 1985, pp. 307-324.

[KIM 02] KIM B., JEONG Y., LIM H.Y., KIM T. S., PARK J. O, DARIO P, MENCIASSI A., and CHOI H., Smart colonoscope system, proceeding of the

http://www.gicare.com/pated/epdgs19.htm

References


2002 International Conference on Intelligent Robotics and Systems EPFL, Lausanne, Switzerland, 2002, pp. 1367 – 1372.

[KIM 03] KIM B., JEONG Y., LIM H.Y., PARK J. O., MENCIASSI A., and DARIO P., Functional colonoscope robot system, proceeding of the 2003 International Conference on Robotics and Automation, Taiwan, 2003, pp. 1092 – 1097.

[KLEIN 87] KLEIN C.A., BLAHO B.E., Dexterity measures for the design and control of kinematically redundant manipulators, International Journal Robot. Res. 7(5), 1987, pp.3-12.

[KUMAR 00] KUMAR S., KASSIM I. M. and ASARI, V. K. Design of a vision-guided microrobotic colonoscopy system, Advanced Robotics, Vol. 14, No.2, 2000, pp. 87-104.

[KWOH 88] KWOH Y., HOU J., JONCKHEERE E., and HAYATI S., A robot with improved absoluted positioning accuraracy for CT guided stereotactic brain surgery, IEEE Transactions on Biomedical Engineering, vol. 35, 1988, pp.153-160.

[LANE 99] LANE D. M., BRUCE J., DAVIES C., ROBINSON G., O’BRIEN D., SNEDDON J., SEATON E., ELFSTROM A., The AMADEUS Dextrous Subsea Hand : Design, Modelling, and Sensor Processing, IEEE Journal of Oceanic Engineering, Vol. 24, No.1, Jan. 1999

[LIM 96] LIM G., MINAMI K., YAMAMOTO K., SUGIHARA M., UCHIYAMA M., ESASHI M., Multi-Link active Catheter snake-like motion. Robotica, 1996, Vol 1, pp. 499-506.

[LIEGEOIS 77] LIEGEOIS A., Automatic supervisory control of the configuration and behavior of multibody mechnisms, IEEE Transaction System, Man and Cybernetics, 7, 1977, 868-871.

[LIN 97] LIN L.M., GAO L.M., YAN G.Z., RONG R., A study on the Endoscope, System Driven by Squirmy Robot, Proceeding of the 1997 IEEE International Conference on Intelligent Processing Systems, Beijing, China, October 28-31, 1997, pp. 75-81.

[LJUNG 99] LJUNG L., System identification : theory for the user, second ed. Upper Saddle River, NJ: Prentice Hall, 1999.

References


[MACIEJEWSKI 85]MACIEJEWSKI A. A., KLEIN C.A., Obstacle avoidance for kinematically redundant manipulators in dynamically varying environments, International Journal of Robot. Res. 4(3), pp. 109-117.

[MAEDA 96] MAEDA S., ABE K., YAMAMOTO K., TOHYAMA O., ITO H., Active Endoscope With SMA (Shape Memory Alloy) Coil Springs, Proceedings of the IEEE 9th Annual International Workshop on Micro Electro Mechanical Systems, San Diego, California, USA, Feb 11-15, 1996, pp. 290 –295.

[MENCIASSI 01]MENCIASSI A., ARENA A., PHEE L., ACOTO D., STEFANINI C., PERNORIO G., GORINI S. BOCCADORO M., CARROZZA M.C., and DARIO P., locomotion issues and mechanisms for microrobots in the gastrointestinal tract, 32nd International Symposium on Robotics, 2001, Seoul, Korea, pp. 428-432.

[MENCIASSI 02]MENCIASSI A., PARK J.H., LEE S., GORINI S., DARIO P., PARK J.O., Robotic solutions and mechanisms for a semi-autonomous Endoscope, IEEE/RSJ International Conference on Intelligent Robots and Systems, IROS 2002, Laussane, Switzerland, 2002, Vol. 2, pp.1379-1384.

[MIDDLETON 90]MIDDLETON R. H., GOODWIN G.C., Digital control and estimation: a unified approach. Englewood Cliffs, N.J. : Prentice Hall, 1990

[MINETA 01] MINETA T., MITSUI T., WATANABE S., KOBAYASHI S., HAGA Y., ESASHI M., Batch fabricated flat meandering shape memory alloy actuator for active catheter, In Journal of Sensors and Actuators A: Physical, Vol./Iss. : 88 /2, 2001, pp.112-120.

[MENSLER 99] MENSLER M., Analyse et étude comparative de méthodes d’identification des systemes, Thèse de Doctorat de UFR Sciences et Techniques Mathématiques Informatique Automatique, 1999, Université Henri Poincaré, Nancy 1, 231p.

[MOCHIYAMA 98]MOCHIYAMA H., SHIMEMURA E., KOBAYASHI H., Shape Correspondence Between a Spatial Curve and a Manipulator with Hyper Degrees of Freedom. IEEE International Conference on Intelligent Robots and Systems,1998, Leuven, Belgium, pp. 161-166.

[MOCHIYAMA 99]MOCHIYAMA H., KOBAYASHI H., The Shape Jacobian of a Manipulator with Hyper Degrees of Freedom.. IEEE Internaional Conference on Robotics and Automation, 1999, Detroit, USA, pp. 2837-2842.

References


[MOCHIYAMA 01]MOCHIYAMA H., Whole-Arm Impedance of a Serial Chain Manipulator, IEEE International Conference on Robotics and Automation, 2001, Seoul, Korea, pp. 2223-2228.

[NAKAMURA 91]NAKAMURA Y., Advanced Robotics: redundancy and Optimization, Reading, Mass.: Addison-Wesley, 1991.

[NATIONAL 44] MILLER B.A., KOLONEL L.N., BERNSTEIN L., Jr.YOUNG J.L., SWANSON G.M., WEST D., KEY C.R., LIFF J.M., GLOVE C.S., and ALEXANDER G.A., Racial/ethnic patterns of cancer in the united states 1988-1992, in NIH pub. 96-4104. Bethesda, MD: Nat. Cancer Inst.,1996

[NCI] National Cancer Institute, http://www.cancer.gov/cancertopics/pdq/treatment/colon/patient (consulté le 23 Janvier 2005)

[NENCHEV 89] NENCHEV D.N., Redundancy Resolution through Local Optimization: A Review,.Journal of Robotic Systems, Vol. 6, pp. 769-798, 1989.

[NORIKA3] http://www.rfnorika.com ((consulté le 23 Janvier 2005)

[OHNO 00] OHNO H., HIROSE S., Study on Slime Robot (Proposal of Slime Robot and Design of Slim Slime Robot),. IEEE Conf. on Intelligent Robots and Systems, 2000, Takamatsu, Japan, pp. 2218-2223.

[OHNO 01] OHNO H., HIROSE S., Design of Slim Slime Robot and its Gait of Locomotion,. Proceeding of the 2001 IEEE/RSJ International Conference on Intelligent Robots and Systems, Hawai, USA, Oct. 2001, pp. 707-715.

[OPPENHEIM 98]OPPENHEIM A., SCHAFER R., Discrete-time signal processing, New Jersey : Prentice Hall, 1998.

[PALJUG 95] PALJUG E., OHM T., HAYATI S., The JPL Serpentine Robot: a 12 DOF System for Inspection,. IEEE Conf. on Robotics and Automation, Nagoya, Japan, 1995, pp. 3143-3148.

[PHEE 97] PHEE S. J., NG W. S., CHEN I.-M.,SEOW-CHOEN F.,DAVIES B.L., Automation of colonoscopy, Part one: Locomotion and Steering Aspects in Automation of colonoscopy, IEEE Engineering in Medicine and Biology Magazine, 1998, Vol. 17, N° 3, pp. 81-88.

http://www.cancer.gov/cancertopics/pdq/treatment/colon/patient

http://www.rfnorika.com/

References


[PIENK 01] PIENKOWSKI P., et la Commission Cancérologie du CREGG, Montauban, France, Enquête sur les réseaux de cancers et la pratique de la cancérologie par les gastro-entérologues en France, Acta Endoscopia, 2001, Vol. 31, n°3.

[PIGNONE 02] PIGNONE M., RICH M., TEUTSCH S.M., BERG. A.O., LOHR K.N., Screening for colorectal cancer in adults at average risk: a summary of the evidence for the US Preventive Services Task Force. Ann Intern Med. Jul 16 2002, 137(2), pp.132-134.

[PINTELON 00] PINTELON R., SCHOUKENS J., ROLAIN Y. Box-Jenkins continuous-time modeling. Automatica 36, 2000, pp.983-991.

[PRELLE 01] PRELLE C., JUTARD A., BETEMPS M., “Compliance adjustment of a metal bellows actuator by control law parameters,” Journal of Mechatronics, Vol. 11, Issue 6, 2001, pp. 631-647.

[ROBINSON 99]ROBISON G., DAVIES J.B.C., Continuum Robots - A State of the Art, IEEE Conf.on Robotics and Automation, Detroit, USA, 1999, pp. 2849-2854.

[SCHOUKENS 91]SCHOUKENS J., PINTELON R., Identification of linear systems- a practical guideline to accurate modeling, London, Pergamon Press, 1991.

[SCHOUKENS 94]SCHOUKENS J., PINTELON R., VAN HAMME H., Identification of linear dynamic systems usinng piecewise constant excitations : use, misuse and alternatives. Automatica 30 (7), 1994,1153-1169.

[SCIAVICCO 00] SCIAVICCO L., SICILIANO B., Modelling and Control of Robot Manipulators, London: Springer, 2000

[SICILIANO 90] SICILIANO B., Kinematic Control of Redundant Robot Manipulators: A Tutorial, Journal of Inteligent and Robotic Systems, Vol. 3, 1990, pp. 201-212.

[SINHA 91] SINHA N. K., RAO G. P., Identification of continuous-time system. Dordrecht: Kluwer Academic, 1991.

[SLATKIN 95] SLATKIN A. B., BURDICK J.W., GRUNDFEST W.S., The Development of a Robotic Endoscope, Proceeding of the International Conference on Intelligent Robots and Systems, Pittsburgh, SA, August, 1995, Vol. 2, pp. 2162-2171.

References


[SAMSON 91] SAMSON C., ESPIAU B., LE BORGNE C., Robot control: The Task function approach, Oxford, UK: Oxford University Press, 1991.

[SMITH 01] SMITH R.A., VON ESCHENBACH A.C., WENDER R., et al. American Cancer Society guidelines for the early detection of cancer: update of early detection guidelines for prostate, colorectal, and endometrial cancers. Also: update 2001 – testing for early lung cancer detection. CA Cancer J clin. Jan-Feb 2001,51(1), pp.38-75.

[SODERSTROM 89]SODERSTROM T. , STOICA P., System identification, New York: Prentice hall, 1989.

[SODERSTROM 00]SODERSTROM T., MOSSBERG M., Performance evaluation of methods for identifying continuous-time autoregressive process. Automatica 36, 2000, pp.53-59.

[STURGES 91] STURGES R.H. and LAOWATTANA S., A Flexible, tendon-controlled device for endoscopy, proceedings of the 1991 IEEE International Conference on Robotics and Automation, Sacramento, USA, 1991, pp. 2582-2591.

[SUZUMORI 91] SUZUMORI K., IIKURA S., TANAKA H., Development of Flexible Microactuator and its Applications to Robotic Mechanisms,. IEEE Conf. on Robotics and Automation, Sacramento, USA, 1991, pp. 1622-1627.

[SUZUMORI 92]SUZUMORI Koichi, IIKURA Shoichi, TANAKA Hirohisa, Applying a Flexible Microactuator to Robotic Mechanisms, IEEE Control Systems Magazine, Volume 12, Issue 1, Feb. 1992 pp. 21-27.

[SUZUMORI 94] SUZUMORI Koichi, KOGA Akihiro, HANEDA Riyiko, Micro fabrication of Integrated FMA using Stereolothography, MEMS '94, Proceedings of the 1994 IEEE Micro Electro Mechanical System, Oiso, Japan, 1994, pp.136-141.

[SUZUMORI 96] SUZUMORI Koichi, KOGA Akihiro, KONDO Fumika, HANEDA Riyoko, Integrated flexible microactuator system, Robotica, 1996, Vol. 14, pp. 493-498.

[THOMANN 03a]THOMANN G., BETEMPS M., REDARCE T., The development of a bendable colonoscopic Tip, IEEE International Conference on Robotic and Automation, ICRA 2003, September 14-19, 2003, Taiwan, pp. 658-663.

References


[THOMANN 03b]THOMANN G., Contribution à la chirurgie minimalement invasive : conception d’un coloscope intelligent : Thèse LAI. Lyon : INSA de Lyon, 2003, 208p. http://csidoc.insa-lyon.fr/these/2003/thomann/ (consulté le 15 Juin 2005)

[THOMANN 04] THOMANN G, REDARCE T., CHEN G., BETEMPS M., First results of the progression of the micro robotic tip for colonoscopy, 35th International Symposium on Robotics (ISR2004), Paris, 2004

[TAYLOR 03] TAYLOR R. and STOIANOVICI D., Medical Robotics in computer-integrated surgery, IEEE Transactions on Robotics and Automation, vol.19, 2003, pp. 765-781

[TROCCAZ 03] TROCCAZ J., Introduction to medical robotics. Tutorial, Summer European University in Surgical Robotics, Montpellier, September,2003

[UNBEHAUEN 87]UNBEHAUEN H., RAO G. P., H. Identification of continuous systems, Amsterdam: North-Holland, 1987.

[URBEHAUEN 90]UNBEHAUEN H., RAO G. P., Continuous-time approaches to system identification – a survey. Automatica, vol. 26. N.1, 1990, pp. 23-35

[UNBEHAUEN 97]UNBEHAUEN H., RAO G. P., Identification of continuous-time systems – a tutorial, Proceedings of the 11th IFAC Symposium System Identification, Vol. 3, Kitakyushu, Fukuoka, Japan, 8-11 July 1997, pp. 1023-1049.

[VUKIBRATOVIC 84]VUKIBRATOVIC M., KIRCANSKI M., A strictly convergent real-time solution for inverse kinematics of robot manipulators, IEEE Transaction System, Man and Cybernetics, 14, 1984, pp.580-586.

[WILSON 93] WILSON J.F., LI D., CHEN Z., GEORGE R.T., Flexible Robot Manipulators and Grippers: Relatives of Elephant Trunks and Squid Tentacles, In: Robots and Biological Systems: Towards a New Bionics?, Berlin: Springer-Verlag, 1993.

[YASHIKAWA 85a]YASHIKAWA T., Dynamic manipulability of robot manipulator, Jounal of robotics systems 2(1), 1985, pp.113-124.

[YASHIKAWA 85b]YASHIKAWA T., Manipulability of robotic mechanisms, International Jounal of robot res. 4(2), 1985, pp.3-9.

http://csidoc.insa-lyon.fr/these/2003/thomann/

References


[YOUNG 91] YOUNG P., Parameter estimation for continuous-time models – A survey, Journal of Automatica, Vol. 17, 1991, pp. 23-29.

FOLIO ADMINISTRATIF

THESE SOUTENUE DEVANT L'INSTITUT NATIONAL DES SCIENCES APPLIQUEES DE LYON

NOM : CHEN DATE de SOUTENANCE : 02/12/2005 (avec précision du nom de jeune fille, le cas échéant) Prénoms : Gang TITRE : Design, modeling and control of a micro-robotic tip for colonoscopy NATURE : Doctorat Numéro d'ordre : 2005- ISAL-00107 Ecole doctorale : Electronique Electrotechnique et Automatique Spécialité : Automatique Industrielle Cote B.I.U. - Lyon : T 50/210/19 / et bis CLASSE : RESUME : La robotique médicale permet à la fois à la chirurgie moderne d’être moins invasive et au chirurgien d’être plus performant. L’incidence pour le patient se traduit en termes de durée de chirurgie moindre, de meilleur confort post-opératoire et de minimisation des risques encourus. Cette thèse porte sur la conception et la commande d’un nouveau type de robot « continuum » afin d'améliorer le procédé de coloscopie. En s’appuyant sur l'analyse détaillée des problèmes spécifiques de la coloscopie traditionnelle et de la suggestion d’un gastro–entérologue, un micro-manipulateur robotisé a été conçu pour guider l'avancement d’un colonoscope pendant son insertion dans un colon.

Ce manipulateur robotisé, appelé EDORA II (Extrémité Distale à ORientation Automatique), a été construit en employant du silicone et utilise un actionnement pneumatique. Trois servovalves ont été utilisées pour commander la pression de trois chambres afin d'obtenir la forme désirée de l'EDORA II. Un nouveau modèle géométrique pour EDORA II a été élaboré en s’appuyant sur la déformation géométrique de l’actionneur. Des essais sur chacune des chambres ont permis de déterminer un comportement non linéaire de l’actionneur, un modèle statique reposant sur une interpolation polynomiale est donc proposé pour rendre compte de ce phénomène. On propose dans cette thèse d’étendre le modèle géométrique classiquement trouvé dans la littérature en rajoutant de nouveaux paramètres qui permettent de tenir compte du couplage entre les chambres. Les résultats comparatifs ont démontré que le modèle géométrique direct proposé reproduit de manière fidèle leur comportement statique.

Un modèle dynamique de comportement reposant sur une analyse des parties mécanique et pneumatique est ensuite présenté. Le système est décomposé en trois sous systèmes indépendants, un pour chaque chambre, chaque sous-système contant deux parties : une partie electro-pneumatique et une partie mécanique. Les ordres des modèles dynamiques de chaque partie sont obtenus par l’expérimentation. Pour déterminer les paramètres intervenant dans le modèle dynamique, la méthode du modèle est choisie. Une analyse fréquentielle et une étude de robustesse nous ont permis de valider ce modèle. Trois capteurs à fibres optiques ont été intégrés sur l’actionneur EDORA II afin de mesurer son éloignement de la paroi du colon. Une validation expérimentale est effectuée dans un tube afin d’évaluer les performances de ce nouveau actionneur. MOTS-CLES : Robotique Chirurgicale, Coloscopie, Chirurgie Mini-Invasive, Robot continuum Laboratoire (s) de recherche : Laboratoire d’Automatique Industrielle, INSA de Lyon Directeur de thèse: Tanneguy REDARCE Président de jury : Philippe BIDAUD Composition du jury : Yacine AMIRAT, Maurice BETEMPS, Michel de MATHELIN, Minh Tu PHAM, Tanneguy REDARCE

Design, modeling and control of a micro-robotic tip for...

Documents

Transcript of Design, modeling and control of a micro-robotic tip for...