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Experiment No.1

The objective of this practice is to carry out an open loop control forow using an AVS-I solenoid valve.

Apparatus:

U!-"

ontrol and Ac#uisition Software

$ater

Procedure:

onnect the interface of the e#uip%ent and the control software.

Select the open loop control & option.

lic' the start button( and start the pu%p.

)ow %anually %ove the AVS-& bar to control the ow through the valvein to the container.

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Experiment No.2

The objective of this practice is to carry out a closed loop controlfor ow by an on*o+ controller using an AVS-I solenoid valve.

Apparatus:

U!-"

ontrol and Ac#uisition Software

$ater

Diagram:

Procedure:

onnect the interface of the e#uip%ent and the control software.

Select the on*o+ control option.

,y double clic'ing on the on*o+ control( select the ow wanted. Thereis certain ow( a tolerance and a perfor%ance ti%e set by default. Itallows the students to play with these para%eters and while seeingthe inuences of each of the%.

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It calculates the inertia of the syste% considering an on*o+ responseand deter%ines the ti%e li%it for an eact control.

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Experiment No.3, 4, 5, 6

The objective of this practice is to carry out a closed loop control for ow by

a PROPORTIONAL (P)CONTROLLER

Apparatus:

U!-

ontrol and Ac#uisition Software

Water

Diagram:

Theory

!I/ controllers use a 0 basic behavior types or %odes1 ! - proportional( I -integrative and / - derivative. $hile proportional and integrative %odes arealso used as single control %odes( a derivative %ode is rarely used on it2sown in control syste%s.

o%binations such as !I and !/ control are very often in practical syste%s.

Proportional controller

A proportional control syste% is a type of linear feedbac'control syste%. The

proportional control syste% is %ore co%ple than an on-o+ control. 3n-o+

control will wor' where the overall syste% has a relatively long response

ti%e( but will result in instability if the syste% being controlled has a rapid

http://en.wikipedia.org/wiki/Feedbackhttp://en.wikipedia.org/wiki/Control_systemhttp://en.wikipedia.org/wiki/On-off_controlhttp://en.wikipedia.org/wiki/Control_systemhttp://en.wikipedia.org/wiki/On-off_controlhttp://en.wikipedia.org/wiki/Feedback

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response ti%e. !roportional control overco%es this by %odulating the output

to the controlling device( such as a continuously variable valve.

In the proportional control algorith%( the controller output is proportional to

the error signal( which is the di+erence between the set pointand

the process variable. In other words( the output of a proportional controller is

the %ultiplication product of the error signal and the proportional gain.

This can be mathematically expressed as

where

: Output of the proportional controller

: Proportional gain

: Instantaneous process error at time t.

SP: Set point

PV: Process variable

Proportional Integral Controller

A PI Controllerproportional!integral controller" is a special case of the PI# controller in which the

derivative #" of the error is not used.

The co%bination of proportional and integral ter%s is i%portant to increasethe speed of the response and also to eli%inate the steady state error. The!I/ controller bloc' is reduced to ! and I bloc's only as shown in 4gure &.

http://en.wikipedia.org/wiki/Setpointhttp://en.wikipedia.org/wiki/Process_variablehttp://en.wikipedia.org/wiki/Setpointhttp://en.wikipedia.org/wiki/Process_variable

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!roportiona Integral 5!I6 ontroller bloc' diagra%

The proportional and integral ter%s is given by1

are the tuning 'nobs( are adjusted to obtain the desired output.

Proportional Derivative Controller

!roportional-/erivative control is useful for fast response controllers that do

not need a steady-state error of 7. !roportional controllers are fast.

/erivative controllers are fast. The two together is very fast. ,elow is areview.

!roportional Action

!roportional action provides an instantaneous response to the control error.

This is useful for i%proving the response of a stable syste% but cannot

control an unstable syste% by itself. Additionally( the gain is the sa%e for all

fre#uencies leaving the syste% with a non8ero steady-state error.

/erivative Action

/erivative action acts on the derivative or rate of change of the control error.

This provides a fast response( as opposed to the integral action( but cannot

acco%odate constant errors 5i.e. the derivative of a constant( non8ero error

is 76. /erivatives have a phase of 9:7 degrees leading to an anticipatory or

predictive response. ;owever( derivative control will produce large control

signals in response to high fre#uency control errors such as set point

changes 5step co%%and6 and %easure%ent noise.

In order to use derivative control the transfer functions %ust be proper. This

often re#uires a pole to be added to the controller 5this pole is not present in

the e#uations below6.

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Proportional Integral derivative controller

A proportional-integral-derivative controller 5!I/ controller6 is a

generic control loopfeedbac' %echanis%5controller6 widely used inindustrial control syste%s. A !I/ controller calculates an The

weighted su% of these three actions is used to adjust the process via a

control ele%ent such as the position of a control valve( a da%per( or the

power supplied to a heating ele%ent.

PID control Theory

The !I/ control sche%e is na%ed after its three correcting ter%s( whose su%

constitutes the %anipulated variable 5?V6. The proportional( integral( and

derivative ter%s are su%%ed to calculate the output of the !I/ controller.

/e4ning as the controller output( the 4nal for% of the !I/ algorith% is1

http://en.wikipedia.org/wiki/Control_loophttp://en.wikipedia.org/wiki/Feedback_mechanismhttp://en.wikipedia.org/wiki/Controller_(control_theory)http://en.wikipedia.org/wiki/Industrial_control_systemhttp://en.wikipedia.org/wiki/Process_variablehttp://en.wikipedia.org/wiki/Setpoint_(control_system)http://en.wikipedia.org/wiki/Algorithmhttp://en.wikipedia.org/wiki/Proportionality_(mathematics)http://en.wikipedia.org/wiki/Integralhttp://en.wikipedia.org/wiki/Derivativehttp://en.wikipedia.org/wiki/Heuristichttp://en.wikipedia.org/wiki/PID_controller#cite_note-1http://en.wikipedia.org/wiki/Control_valvehttp://en.wikipedia.org/wiki/Damper_(flow)http://en.wikipedia.org/wiki/Control_loophttp://en.wikipedia.org/wiki/Feedback_mechanismhttp://en.wikipedia.org/wiki/Controller_(control_theory)http://en.wikipedia.org/wiki/Industrial_control_systemhttp://en.wikipedia.org/wiki/Process_variablehttp://en.wikipedia.org/wiki/Setpoint_(control_system)http://en.wikipedia.org/wiki/Algorithmhttp://en.wikipedia.org/wiki/Proportionality_(mathematics)http://en.wikipedia.org/wiki/Integralhttp://en.wikipedia.org/wiki/Derivativehttp://en.wikipedia.org/wiki/Heuristichttp://en.wikipedia.org/wiki/PID_controller#cite_note-1http://en.wikipedia.org/wiki/Control_valvehttp://en.wikipedia.org/wiki/Damper_(flow)

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where

1 !roportional gain( a tuning para%eter

1 Integral gain( a tuning para%eter

1 /erivative gain( a tuning para%eter

1 @rror

1 Ti%e or instantaneous ti%e 5the present6

1 Variable of integration ta'es on values fro% ti%e 7 to the present

!roportional ter%

The proportional ter% produces an output value that is proportional to the

current error value. The proportional response can be adjusted by %ultiplying

the error by a constant Bp( called the proportional gain constant.

The proportional ter% is given by1

A high proportional gain results in a large change in the output for a given

change in the error. If the proportional gain is too high( the syste% can

beco%e unstable contrast( a s%all gain results in a s%all output response to

a large input error( and a less responsive or less sensitive controller. If the

proportional gain is too low( the control action %ay be too s%all when

responding to syste% disturbances. Tuning theory and industrial practice

indicate that the proportional ter% should contribute the bul' of the output

change

Integral termThe contribution fro% the integral ter% is proportional to both the %agnitude

of the error and the duration of the error. The integralin a !I/ controller is

the su% of the instantaneous error over ti%e and gives the accu%ulated

o+set that should have been corrected previously. The accu%ulated error is

then %ultiplied by the integral gain 5 6 and added to the controller output.

The integral ter% is given by1

http://en.wikipedia.org/wiki/Integralhttp://en.wikipedia.org/wiki/Integral

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The integral ter% accelerates the %ove%ent of the process towards set point

and eli%inates the residual steady-state error that occurs with a pure

proportional controller. ;owever( since the integral ter% responds to

accu%ulated errors fro% the past( it can cause the present value

to overshootthe set point value

Derivative Term

The derivativeof the process error is calculated by determining the slope of the error over time and

multiplying this rate of change by the derivative gain . The magnitude of the contribution of the

derivative term to the overall control action is termed the derivative gain$ .

The derivative term is given by:

#erivative action predicts system behavior and thus improves settling time and stability of the system

Procedure:

onnect the interface of the e#uip%ent and the control software.

Select the control on*o+ option.

?a'e a double clic' on the on*o+ control( select the ow wanted.there are certain ow( a tolerance and a perfor%ance ti%e set bydefault. It allows the students to play with these para%eters and seethe inuences of each one.

The level control can be carried out by the activation of a singleactuator( or of several ones( to which di+erent tolerances are allowed.These controllers wor' as security syste% %easures when thecontrolled variable eceeds in a tolerance the set value. To activate or

http://en.wikipedia.org/wiki/Overshoot_(signal)http://en.wikipedia.org/wiki/Derivativehttp://en.wikipedia.org/wiki/Overshoot_(signal)http://en.wikipedia.org/wiki/Derivative

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to disable any of these controllers you %ay have to double clic' oneach of the% and press the button

alculate the inertia of the syste% for an on*o+ response and deter%ine theli%it ti%e for an eact control.

Experiment No. 7

Use several inputs to i%ple%ent logic 3C D A)/ Eates with thepurpose of activating an output. $ith the activation of F or 0 inputs( theoutput will be activated.

Theory

ontrol engineering has evolved over ti%e. In the past hu%ans were the

%ain %ethod for con-trolling a syste%. ?ore recently electricity has been

used for control and early electrical control was based on relays. These

relays allow power to be switched on and o+ without a %echanical switch. It

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is co%%on to use relays to %a'e si%ple logical control decisions. The

develop%ent of low cost co%puter has brought the %ost recent revolution(

the !rogra%%able ogic ontroller 5!6. The advent of the ! began in the

&:G7s( and has beco%e the %ost co%%on choice for %anufacturing controls.

!s have been gaining popularity on the factory oor and will probablyre%ain predo%inant for so%e ti%e to co%e. ?ost of this is because of the

advantages they o+er.

ost e+ective for controlling co%ple syste%s.

"leible and can be reapplied to control other syste%s #uic'ly and

easily.

o%putational abilities allow %ore sophisticated control.

Trouble shooting aids %a'e progra%%ing easier and reduce downti%e.

Celiable co%ponents %a'e these li'ely to operate for years before

failure.

Ladder Logic

adder logic is the %ain progra%%ing %ethod used for !s. As %entioned

before( ladder logic has been developed to %i%ic relay logic. The decision to

use the relay logic diagra%s was a strategic one. ,y selecting ladder logic as

the %ain progra%%ing %ethod( the a%ount of retraining needed for

engineers and tradespeople was greatly reduced.

?odern control syste%s still include relays( but these are rarely used forlogic. A relay is a si%ple device that uses a %agnetic 4eld to control a switch(

as pictured in "igure F. $hen a voltage is applied to the input coil( the

resulting current creates a %agnetic 4eld. The %agnetic 4eld pulls a %etal

switch 5or reed6 towards it and the contacts touch( closing the switch. The

contact that closes when the coil is energi8ed is called nor%ally open. The

nor%ally closed contacts touch when the input coil is not energi8ed. Celays

are nor%ally drawn in sche%atic for% using a circle to represent the input

coil. The output contacts are shown with two parallel lines. )or%ally open

contacts are shown as two lines( and will be open 5non-conducting6 when the

input is not energi8ed. )or%ally closed contacts are shown with two lineswith a diagonal line through the%. $hen the input coil is not energi8ed the

nor%ally closed contacts will be closed 5conducting6.

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Procedure

1. "irst( we %ay create a project for this new practice.

2. In this second step we %ay place the contacts over networ'& and we %aycon4gure the% ade#uately( as shown in the following 4gure.

3. )et( we join the contacts and chec' the progra%.

4. $e load the application in the !@( save and close our project.

5.Then( we %ay chec' the ade#uate operation of the ! through the !@.In order to do so(we will connect Sw7 with /I7( Sw& to /I& and SwF with /IF.$e %ay activate F of the 0 Switches 5any will do6 and we %ay chec' the /H&output is activated. $e %ay connect as well /I7( /I& and /IF with !b7( !b&and !bF respectively.

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