Conception des logiciels critiques dans le domaine spatial
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Transcript of Conception des logiciels critiques dans le domaine spatial
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Conception des logiciels critiquesConception des logiciels critiquesdans le domaine spatialdans le domaine spatial
Du système au logiciel...Du système au logiciel...
Retour d’expérience sur les méthodes formellesRetour d’expérience sur les méthodes formelles
David LESENS
EADS LAUNCH VEHICLES, Route de Verneuil
BP 2, F-78133 Les Mureaux Cedex – France
Email : [email protected]
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Plan
EADS LAUNCH VEHICLES Qui nous sommes
Méthodologie de développement d’un système véhicule Développement Validation
Les méthodes formelles de spécification logicielle Pourquoi Comment
Retour d’expérience L’Automatic Transfer Vehicle
• Spécification du logiciel MSU• Bilan
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EADS : Un acteur majeur de l’industrie aéronautique et de défense
n° 3 mondial - n° 1 européen
CA 2000* : 24,2 Mds €Prise de commandes 2000*: 49,3 Mds €
* valeur pro forma
0 10 20 30 40 50 60
Boeing
Lockheed-Martin
EADS
Bae-Systéms
Raytheon
Northrop
Thales
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European Aeronautics Defence and Space companyLAUNCH VEHICLES
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Activités phares d’EADS LAUNCH VEHICLES
Systèmesstratégiques
M4 / M5M51Maîtrise d’œuvre systèmes complets
Transport spatial
Ariane 4Ariane 5
ATV
Soyuz
Lanceurs complémentaires
ARD
ARES THEMIS
Equipements Equipements spatiaux
Produits satellites
Produits technologiques et divers
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697,7 Millions €
50 Millions €
295,8 Millions €
CA 2000 : 1043,5 Millions €
67%Transport spatial civil
5%Equipements
28%Lanceurs stratégiques
Chiffre d’affaires par activité
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Plan
EADS LAUNCH VEHICLES Qui nous sommes
Méthodologie de développement d’un système véhicule Développement Validation
Les méthodes formelles de spécification logicielle Pourquoi Comment
Retour d’expérience L’Automatic Transfer Vehicle
• Spécification du logiciel MSU• Bilan
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Développement d’un logiciel spatial
Spécification véhicule
Conception véhicule
Spécificationéquipements
Spécificationlogicielles
Développement
Simulateur Développement
Gestion demission
Communication Thermique
Puissance
Propulsion
Algorithmesnavigation,guidage, control
Panneauxsolaires
Développement
I/F I/F
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Validation du logiciel
Le premier vol est un vol de qualification
Logiciel réel
Simulateurs des équipements
Simulateur de l’environnement
Equipements réels
Simulation d’un vol complet
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Objectif de la spécification logicielle
Capturer le besoin système Spécialistes métiers
Servir d’entrée à l’activité de développement Cohérence Complétude
Référence pour la validation fonctionnelle Exigences validables
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Plan
EADS LAUNCH VEHICLES Qui nous sommes
Méthodologie de développement d’un système véhicule Développement Validation
Les méthodes formelles de spécification logicielle Pourquoi Comment
Retour d’expérience L’Automatic Transfer Vehicle
• Spécification du logiciel MSU• Bilan
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Pourquoi utiliser des méthodes formelles ?
Raffinement
Etudes Systèmes
Qualification
Spécification Technique
Conception
Développement Tests Unitaires
Intégration
ValidationFonctionnelle
Diminution des corrections tardives
Ecriture desspécifications en méthode formelle
Repriseimmédiate
Spécification« validable »
Génération de tests
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1er objectif des méthodes formelles de spécification
Augmenter la formalisation de notre spécification
Standard de communication• Pour des informaticiens• Pour des non informaticiens
Différents types d’application• Synchrone et/ou• Asynchrone et/ou• Algorithmique
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2nd objectif des méthodes formelles de spécification
Détecter les erreurs en phase amont de développement
Validation de la spécification• Cohérence de la spécification• Complétude de la spécification• Preuve sur la spécification
Test• Prototypage rapide• Simulation de la spécification
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3ième objectif des méthodes formelles de spécification
Faciliter le raffinement de la spécification vers une conception
Réutilisation des tests de simulation de la spécification Ecriture d’une conception à l’aide d’une méthode formelle ? Génération de code
• Séquentiel ou multitâche• Langage cible• Embarquable ?
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Et en pratique ? Soyons pragmatiques !Retour d’expérience
Les méthodes formelles sont lourdes à utiliser Utiliser selon les besoins
Modélisation statique Type SADT ou SART
• Vérification de la cohérence des flots de données
Modélisation dynamique Mieux comprendre un point dur Simulation / validation
Spécification Développement complet
Spécification véhicule ou code embarquable
Choix de la méthode
En support d’une spécification ou d’une analyse
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Quelles méthodes « formelles » choisir?
Systèmevéhicule
Etudesalgorithmiques
SimulinkJames
SDL,StateCharts
Spécification logicielle
Conception logicielle
Codage
ScadeSignalEsterel
Méthode B
Exemples d’applications
UML
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Plan
EADS LAUNCH VEHICLES Qui nous sommes
Méthodologie de développement d’un système véhicule Développement Validation
Les méthodes formelles de spécification logicielle Pourquoi Comment
Retour d’expérience L’Automatic Transfer Vehicle
• Spécification du logiciel MSU• Bilan
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Retours d’expérience à EADS Launch Véhicles
Spécification système Chaîne de sécurité ATV
• Sol / Système de communication• Pool d’ordinateurs de bord / bus / liens filaires• Système de sécurité (MSU) et logiciel associé
Spécification logicielle Architecture du GNC Ariane 5
• Cyclique / synchrone• Multi-fréquence, condition d ’activation
Séquentiel Ariane 5• Asynchrone couplé au synchrone
Logiciel MSU• Sécurité ATV / ISS
Etudes amont En SDL
Etudes amont Rétro ingénierie en SCADE Etudes amont Rétro ingénierie en SDL
Développement opérationnelen SCADE
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The Automated Transfer Vehicle (ATV) context
One of the European contributions to the International Space Station (ISS).
It will supply from 2004 onward the following services to the ISS:
Refuelling, ISS orbit correction, Freight delivery, ISS trash destruction.
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ATV safety chain and Collision Avoidance maneuver
Healthstatus
Reset
MSU 1
Safety Chain
MSU 2
Sensors
Thrusters
Responsible of ISS safety by triggering a CAM
2 redundant chains Coded in ADA No ADA exception Single task
DPU 1
FTCP
DPU 2
DPU 3
• Rendezvousmonitoring
• Red button
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How the MSU software is specified ?
GNC algorithms
Algorithms Reference DocumentsAlgorithms Reference Documents
Technical Specification of the MSU SWTechnical Specification of the MSU SW
• State automaton• MSU SW architecture• CAM sequencer
SCADE modeling
• Non functional requirements• Functional requirements
FrameMaker editor
+
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Contains of the MSU SW SCADE model
Navigation
Monitoring
Control
Activation condition
Data flowdescription
Post-CAM
CAM
Hierarchicaldecomposition
FBY 2Data ageing
Synchronous and cycle architecture
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Formal semantics
Validation of a SCADE specification
Formalproof
Specification• Complete• Coherent• Implementable
No ambiguous Easy to understand (graphic) Well accepted by the participants
Semanticsverifier
Executablespecification
Spec validation• Code generation• Simulation
Validation improprement• Exhaustiveness• Automatic
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Formal proofs on the MSU SW TS
SCADEmodel
Environmentdescription
LogicalProperty
Exhaustive verification
LESAR tools
True property
Diagnostic
LESAR tool is developed by the VERIMAG laboratory
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Properties description
Use of synchronous observer, specified In SCADE In LUSTRE Using regular expression
Observedsoftware
Environment
Properties
InputsOutputs
Environmentoracle
Propertiesoracle
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Proof by model checking
Construction of a mathematical model of the SCADE model Computation of the reachable states Comparison with the forbidden states
Forbiddenstates
Initialstates
SCADEmodel
Mathematicalmodel
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Property examples
A CAM test can only be triggered by a “red button” signal true_after_false( CAM_TEST_TRIG ) RED_BUTTON No assertion is required from the environment to satisfy this property.
When the initialisation of the two MSU chains is correct, they can not triggered both a CAM at the same time #( MSU1_CAM_TRIG , MSU2_CAM_TRIG ) It is satisfied only when the initialisation of the 2 MSU is correct cam_arm( SWITCH_ON_MSU1, ARM_MSU1, SWITCH_ON_MSU2, ARM_MSU2,
RED_BUTTON )
on1 arm1 on2 arm2Init S1 S2 S3 S4
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Conclusion on formal method use for ATV
Improve the Improve the qualityqualityof the TS of the TS
of the MSU Softwareof the MSU Software
- Description of a MSU cyclic andsynchronous architecture
- Formal semantics (no ambiguity,no incoherence)
. Data flow / Activation condition
. Data obsolescence description- MSU SW TS easy to understand- Semantics verification / Formal proof
Not usable for aNot usable for acomplexcomplex software software
- Non adapted for asynchronoussoftware
- Limited to small, cyclic, synchronoussoftware
- Start of the MSU software design
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Complex software (1): level of description ?
Dataupdate
Communicationsystem
Algorithms
GNC
TC TM TC
Dataupdate Algorithms
TM
cmd ack
Synchronous specificationAsynchronous specification
Communication system
GNC
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Measurement
Bus frame
Software
Complex software (2): synchronous hypothesis (1)
Algo
Cmd
Cycle nCycle n-1 Cycle n+1
Algo period
Algo Algo
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Complex software (2): synchronous hypothesis (2)
Bus frame
Software
Measurement Cmd
AlgoAlgo Algo
Cycle nCycle n-1 Cycle n+1
Algo period
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AlgoAlgo Algo
Complex software (2): synchronous hypothesis (3)
Bus frame
Software
Measurement Cmd
Cycle nCycle n-1 Cycle n+1
Algo period
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Plan
EADS LAUNCH VEHICLES Qui nous sommes
Méthodologie de développement d’un système véhicule Développement Validation
Les méthodes formelles de spécification logicielle Pourquoi Comment
Retour d’expérience L’Automatic Transfer Vehicle
• Spécification du logiciel MSU• Bilan
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Conclusion: Comment utiliser les méthodes formelles
En rétro-ingénierie Développement d’un modèle formel
• A partir d’une spécification logicielle• Pour analyser un point particulier
Trois étapes en développement Spécification
• Quand débuter le développement ? Maturité du besoin• Précision de la description ? Positionnement dans le cycle
Validation de la spécification• Nouvelle activité à planifier et à financer
Raffinement vers du code• Evolution du cycle de développement
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Prospectives (1)
Amélioration des techniques utilisées Des techniques de spécification
Mixer synchrone et asynchrone Raffiner de l’asynchrone vers du synchrone ...
Des techniques de preuve Spécification des propriétés Puissance des outils ...
Des techniques de conception Langages de compilation Architectures multi-tâches ...
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Prospectives (2)
Amélioration de la méthodologie
Etendre l’approche formelle au système véhicule Utilisation par des non informaticiens Raffinement
Rendre systématique l’approche formelle Utilisation dans les futures projets Systèmes critiques et moins critiques Culture d’entreprise