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ControlandSimulation
inLabVIEW
Hans-PetterHalvorsen








ControlandSimulationinLabVIEW


Hans-PetterHalvorsen
Copyright©2017


E-Mail:
Web:g

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Preface
ThisdocumentexplainsthebasicconceptsofusingLabVIEWforControlandSimulation
purposes.

FormoreinformationaboutLabVIEW,visitmyBlog:g.

Youneedthefollowingsoftware:
•
•
•
•
•









LabVIEW
LabVIEWControlDesignandSimulationModule

LabVIEWMathScriptRTModule
NI-DAQmx
NIMeasurement&AutomationExplorer




TableofContents
Preface......................................................................................................................................3
TableofContents.....................................................................................................................iv
1

IntroductiontoLabVIEW...................................................................................................1
1.1

Dataflowprogramming...............................................................................................1

1.2

Graphicalprogramming..............................................................................................1

1.3

Benefits.......................................................................................................................2

2

IntroductiontoControlandSimulation............................................................................3

3

IntroductiontoControlandSimulationinLabVIEW.........................................................4
3.1

3.1.1

Simulation............................................................................................................5

3.1.2

ControlDesign.....................................................................................................5

3.2

LabVIEWPIDandFuzzyLogicToolkit..........................................................................6

3.2.1

PIDControl..........................................................................................................6

3.2.2

FuzzyLogic...........................................................................................................6

3.3
4

LabVIEWControlDesignandSimulationModule.......................................................4

LabVIEWSystemIdentificationToolkit.......................................................................7

Simulation.........................................................................................................................8
4.1

SimulationinLabVIEW................................................................................................8

4.2

SimulationSubsystem...............................................................................................13

4.3

ContinuousLinearSystems.......................................................................................14

Exercises..............................................................................................................................19
5

PIDControl......................................................................................................................31
5.1

PIDControlinLabVIEW............................................................................................32
iv




v


5.2

6

SystemIdentificationinLabVIEW.............................................................................35

FuzzyLogic.......................................................................................................................36
8.1

9

ControlDesigninLabVIEW.......................................................................................34

SystemIdentification.......................................................................................................35
7.1

8

Auto-tuning...............................................................................................................33

ControlDesign.................................................................................................................34
6.1

7

TableofContents

FuzzyLogicinLabVIEW.............................................................................................36

LabVIEWMathScript.......................................................................................................38
9.1

Help...........................................................................................................................39

9.2

Examples...................................................................................................................39

9.3

Usefulcommands.....................................................................................................42

9.4

Plotting.....................................................................................................................42

10 Discretization...................................................................................................................43
10.1 Low-passFilter..........................................................................................................43
10.2 PIController..............................................................................................................46
10.2.1 PIControllerasaState-spacemodel.................................................................49
10.3 ProcessModel..........................................................................................................50


Tutorial: Control and Simulation in LabVIEW




1 IntroductiontoLabVIEW
LabVIEW(shortforLaboratoryVirtualInstrumentationEngineeringWorkbench)isa
platformanddevelopmentenvironmentforavisualprogramminglanguagefromNational

Instruments.Thegraphicallanguageisnamed"G".OriginallyreleasedfortheApple
Macintoshin1986,LabVIEWiscommonlyusedfordataacquisition,instrumentcontrol,and
industrialautomationonavarietyofplatformsincludingMicrosoftWindows,variousflavors
ofLinux,andMacOSX.VisitNationalInstrumentsatwww.ni.com.
Thecodefileshavetheextension“.vi”,whichisanabbreviationfor“VirtualInstrument”.
LabVIEWofferslotsofadditionalAdd-OnsandToolkits.

1.1 Dataflowprogramming
TheprogramminglanguageusedinLabVIEW,alsoreferredtoasG,isadataflow
programminglanguage.Executionisdeterminedbythestructureofagraphicalblock
diagram(theLV-sourcecode)onwhichtheprogrammerconnectsdifferentfunction-nodes
bydrawingwires.Thesewirespropagatevariablesandanynodecanexecuteassoonasall
itsinputdatabecomeavailable.Sincethismightbethecaseformultiplenodes
simultaneously,Gisinherentlycapableofparallelexecution.Multi-processingandmultithreadinghardwareisautomaticallyexploitedbythebuilt-inscheduler,whichmultiplexes
multipleOSthreadsoverthenodesreadyforexecution.

1.2 Graphicalprogramming
LabVIEWtiesthecreationofuserinterfaces(calledfrontpanels)intothedevelopmentcycle.
LabVIEWprograms/subroutinesarecalledvirtualinstruments(VIs).EachVIhasthree
components:ablockdiagram,afrontpanel,andaconnectorpanel.Thelastisusedto
representtheVIintheblockdiagramsofother,callingVIs.Controlsandindicatorsonthe
frontpanelallowanoperatortoinputdataintoorextractdatafromarunningvirtual
instrument.However,thefrontpanelcanalsoserveasaprogrammaticinterface.Thusa
virtualinstrumentcaneitherberunasaprogram,withthefrontpanelservingasauser
interface,or,whendroppedasanodeontotheblockdiagram,thefrontpaneldefinesthe
inputsandoutputsforthegivennodethroughtheconnectorpane.ThisimplieseachVIcan
beeasilytestedbeforebeingembeddedasasubroutineintoalargerprogram.
1

2



IntroductiontoLabVIEW

Thegraphicalapproachalsoallowsnon-programmerstobuildprogramssimplybydragging
anddroppingvirtualrepresentationsoflabequipmentwithwhichtheyarealreadyfamiliar.
TheLabVIEWprogrammingenvironment,withtheincludedexamplesandthe
documentation,makesitsimpletocreatesmallapplications.Thisisabenefitononeside,
butthereisalsoacertaindangerofunderestimatingtheexpertiseneededforgoodquality
"G"programming.Forcomplexalgorithmsorlarge-scalecode,itisimportantthatthe
programmerpossessanextensiveknowledgeofthespecialLabVIEWsyntaxandthe
topologyofitsmemorymanagement.ThemostadvancedLabVIEWdevelopmentsystems
offerthepossibilityofbuildingstand-aloneapplications.Furthermore,itispossibletocreate
distributedapplications,whichcommunicatebyaclient/serverscheme,andaretherefore
easiertoimplementduetotheinherentlyparallelnatureofG-code.

1.3 Benefits
OnebenefitofLabVIEWoverotherdevelopmentenvironmentsistheextensivesupportfor
accessinginstrumentationhardware.Driversandabstractionlayersformanydifferenttypes
ofinstrumentsandbusesareincludedorareavailableforinclusion.Thesepresent
themselvesasgraphicalnodes.Theabstractionlayersofferstandardsoftwareinterfacesto
communicatewithhardwaredevices.Theprovideddriverinterfacessaveprogram
developmenttime.ThesalespitchofNationalInstrumentsis,therefore,thatevenpeople
withlimitedcodingexperiencecanwriteprogramsanddeploytestsolutionsinareduced
timeframewhencomparedtomoreconventionalorcompetingsystems.Anewhardware
drivertopology(DAQmxBase),whichconsistsmainlyofG-codedcomponentswithonlya
fewregistercallsthroughNIMeasurementHardwareDDK(DriverDevelopmentKit)

functions,providesplatformindependenthardwareaccesstonumerousdataacquisition
andinstrumentationdevices.TheDAQmxBasedriverisavailableforLabVIEWonWindows,
MacOSXandLinuxplatforms.


Tutorial: Control and Simulation in LabVIEW




2 IntroductiontoControland
Simulation
Controldesignisaprocessthatinvolvesdevelopingmathematicalmodelsthatdescribea
physicalsystem,analyzingthemodelstolearnabouttheirdynamiccharacteristics,and
creatingacontrollertoachievecertaindynamiccharacteristics.
Simulationisaprocessthatinvolvesusingsoftwaretorecreateandanalyzethebehaviorof
dynamicsystems.Youusethesimulationprocesstolowerproductdevelopmentcostsby
acceleratingproductdevelopment.Youalsousethesimulationprocesstoprovideinsight
intothebehaviorofdynamicsystemsyoucannotreplicateconvenientlyinthelaboratory.
Belowweseeaclosed-loopfeedbackcontrolsystem:



3





3 ControlandSimulationin

LabVIEW
LabVIEWhasseveraladditionalmodulesandToolkitsforControlandSimulationpurposes,
e.g.,“LabVIEWControlDesignandSimulationModule”,“LabVIEWPIDandFuzzyLogic
Toolkit”,“LabVIEWSystemIdentificationToolkit”and“LabVIEWSimulationInterface
Toolkit”.LabVIEWMathScriptisalsousefulforControlDesignandSimulation.
•
•
•
•

LabVIEWControlDesignandSimulationModule
LabVIEWPIDandFuzzyLogicToolkit
LabVIEWSystemIdentificationToolkit
LabVIEWSimulationInterfaceToolkit

Thistutorialwillfocusonthemainaspectsinthesemodulesandtoolkits.
AllVIsrelatedtothesemodulesandtoolkitsareplacedintheControlDesignandSimulation
Toolkit:



3.1 LabVIEWControlDesignandSimulation
Module
WithLabVIEWControlDesignandSimulationModuleyoucanconstructplantandcontrol
modelsusingtransferfunction,state-space,orzero-pole-gain.Analyzesystemperformance
withtoolssuchasstepresponse,pole-zeromaps,andBodeplots.Simulatelinear,nonlinear,
anddiscretesystemswithawideoptionofsolvers.WiththeNILabVIEWControlDesignand
4

5



ControlandSimulationinLabVIEW

SimulationModule,youcananalyzeopen-loopmodelbehavior,designclosed-loop
controllers,simulateonlineandofflinesystems,andconductphysicalimplementations.

3.1.1

Simulation

TheSimulationpaletteinLabVIEW:


ThemainfeaturesintheSimulationpaletteare:
•
•

•

ControlandSimulationLoop-YoumustplaceallSimulationfunctionswithina
Control&SimulationLooporinasimulationsubsystem.
ContinuousLinearSystemsFunctions-UsetheContinuousLinearSystemsfunctions
torepresentcontinuouslinearsystemsofdifferentialequationsonthesimulation
diagram.
SignalArithmeticFunctions-UsetheSignalArithmeticfunctionstoperformbasic
arithmeticoperationsonsignalsinasimulationsystem.

3.1.2

ControlDesign

TheControlDesignpaletteinLabVIEW:

Tutorial: Control and Simulation in LabVIEW


6



ControlandSimulationinLabVIEW



3.2 LabVIEWPIDandFuzzyLogicToolkit
TheNILabVIEWPIDandFuzzyLogicToolkitaddcontrolalgorithmstoLabVIEW.By
combiningthePIDandfuzzylogiccontrolfunctionsinthistoolkitwiththemathandlogic
functionsinLabVIEWsoftware,youcanquicklydevelopprogramsforautomatedcontrol.
Youmayintegratethesecontroltoolswiththepowerofdataacquisition.

3.2.1

PIDControl

ThePIDpaletteinLabVIEW:

3.2.2

FuzzyLogic

TheFuzzyLogicpaletteinLabVIEW:
Tutorial: Control and Simulation in LabVIEW


7



ControlandSimulationinLabVIEW



3.3 LabVIEWSystemIdentificationToolkit
The“LabVIEWSystemIdentificationToolkit”combinesdataacquisitiontoolswithsystem
identificationalgorithmsforplantmodeling.YoucanusetheLabVIEWSystemIdentification
Toolkittofindempiricalmodelsfromrealplantstimulus-responseinformation.
TheSystemIdentificationpaletteinLabVIEW:



Tutorial: Control and Simulation in LabVIEW

4 Simulation
Simulationisaprocessthatinvolvesusingsoftwaretorecreateandanalyzethebehaviorof
dynamicsystems.Youusethesimulationprocesstolowerproductdevelopmentcostsby
acceleratingproductdevelopment.Youalsousethesimulationprocesstoprovideinsight
intothebehaviorofdynamicsystemsyoucannotreplicateconvenientlyinthelaboratory.
Forexample,simulatingajetenginesavestime,labor,andmoneycomparedtobuilding,
testing,andrebuildinganactualjetengine.YoucanusetheLabVIEWControlDesignand
SimulationModuletosimulateadynamicsystemoracomponentofadynamicsystem.For
example,youcansimulateonlytheplantwhileusinghardwareforthecontroller,actuators,
andsensors(Hardware-in-the-loopSimulation).
Adynamicsystemmodelisadifferentialordifferenceequationthatdescribesthebehavior
ofthedynamicsystem.

4.1 SimulationinLabVIEW
UsetheSimulationVIsandfunctionstocreatesimulationapplicationsinLabVIEW.Inthe
ControlDesign&SimulationpalettewehavetheSimulationSubpalette:


BelowweseetheSimulationSubpalette:

8



9



Simulation

Note!Allthe“Blocks”intheSimulationpalettearenotSubVIs,i.e.,wecannotdouble-click
onthemandopentheBlockDiagrambecausetheyhavenone.AlltheBlocksinthe
SimulationpalettemustbeusedinsidetheControlandSimulationLoop(explainedbelow).
ControlandSimulationLoop:
Inthe“Simulation”Subpalettewehavethe“ControlandSimulationLoop”whichisvery
usefulinsimulations:

YoumustplaceallSimulationfunctionswithinaControl&SimulationLooporinasimulation
subsystem.YoualsocanplacesimulationsubsystemswithinaControl&SimulationLoopor
anothersimulationsubsystem,oryoucanplacesimulationsubsystemsonablockdiagram
outsideaControl&SimulationLooporrunthesimulationsubsystemsasstand-aloneVIs.

Tutorial: Control and Simulation in LabVIEW


10



Simulation


TheControl&SimulationLoophasanInputNode(upperleftcorner)andanOutputNode
(upperrightcorner).UsetheInputNodetoconfiguresimulationparameters
programmatically.YoualsocanconfiguretheseparametersinteractivelyusingtheConfigure
SimulationParametersdialogbox.Accessthisdialogboxbydouble-clickingtheInputNode
orbyright-clickingtheborderandselectingConfigureSimulationParametersfromthe
shortcutmenu.

Configuration:
Whenyouplacetheseblocksonthediagramyoumaydouble-clickorright-clickandthen
select“Configuration…”
Example:ConfigurationDialogbox
Forthe“TransferFunction”(Simulation→ContinuousLinearSystems)blockwehave
thefollowingConfigurationwindow:

Tutorial: Control and Simulation in LabVIEW


11



Simulation


AllthedifferentblockshavetheirowndifferentConfigurationwindow.


IntheParametersourceyoumayselectbetween:
•
•

ConfigurationDialogBox
Terminal

Ifyouselect“ConfigurationDialogBox”youentertheconfigurationintheConfiguration
windowlikeweseeabove,whileifyouselect“Terminal”thatspecificconfigurationisset
fromtheBlockDiagramlikethis:

IconStyle:
Whenyouplacetheblockontheblockdiagramyoumayselecthowthatshouldappear.
Right-clickontheblock/iconandselect“IconStyle”:

Tutorial: Control and Simulation in LabVIEW


12



Simulation


Example:IconStyle
Forthe“TransferFunction”(Simulation→ContinuousLinearSystems)blockwehave
thefollowingdifferenticonstyles:
Static:

Dynamic:


TextOnly:


Express:

WeseefortheDynamicandExpressstylesthattheappearancechangesaccordingto
configurationparametersweset.

Tutorial: Control and Simulation in LabVIEW


13



Simulation

Ipersonallypreferthe“static”iconstylebecauseitdoesnotrequirelotsofspaceonthe
diagram.

4.2 SimulationSubsystem
YoumaycreateaSimulationSubsystem(File→New…):


TheSimulationSubsystemisveryusefulwhendealingwithlargersimulationsystemsin
ordertocreateamorestructuredcode.Irecommendthatyou(always)usethisfeature.
TheSimulationSubsystemisalmostequaltoanormalLabVIEWBlockDiagrambutnoticethe
backgroundcolorisslightlydarker.
Note!InordertoopentheSimulationSubsystem,right-clickandselect“OpenSubsystem”.
TheSimulationSubsystemmayalsoberepresentedbydifferenticons.Ifyouselect
“dynamic”iconstyle,youwillseea“miniature”versionofthesubsystemlikethis:

Tutorial: Control and Simulation in LabVIEW

14



Simulation


Youmaydraginthecornerinordertoincreaseordecreasethedynamicicon.
Ifyouselect“static”iconstyleyouseetheiconyoucreatedwiththeIconEditor.


Likethis:





4.3 ContinuousLinearSystems
Inthe“ContinuousLinearSystems”Subpalettewewanttocreateasimulationmodel:


ThemostusedblocksprobablyareIntegrator,TransportDelay,State-SpaceandTransfer
Function.
Tutorial: Control and Simulation in LabVIEW


15

Simulation

Whenyouplacetheseblocksonthediagramyoumaydouble-clickorright-clickandthen
select“Configuration…”
Integrator-Integratesacontinuousinputsignalusingtheordinarydifferential
equation(ODE)solveryouspecifyforthesimulation.
TheConfigurationwindowfortheIntegratorblocklookslikethis:


TransportDelay-Delaystheinputsignalbytheamountoftimeyouspecify.
TheConfigurationwindowfortheTransportDelayblocklookslikethis:



TransferFunction-Implementsasystemmodelintransferfunctionform.Youdefine
thesystemmodelbyspecifyingtheNumeratorandDenominatorofthetransferfunction
equation.
Tutorial: Control and Simulation in LabVIEW


16



Simulation

TheConfigurationwindowfortheTransferFunctionblocklookslikethis:


State-Space-Implementsasystemmodelinstate-spaceform.Youdefinethesystem

modelbyspecifyingtheinput,output,state,anddirecttransmissionmatrices.
TheConfigurationwindowfortheState-Spaceblocklookslikethis:



SignalArithmetic:
The“SignalArithmetic”Subpaletteisalsousefulwhencreatingasimulationmodel:

Tutorial: Control and Simulation in LabVIEW


17



Simulation



Example:SimulationModel
BelowweseeanexampleofasimulationmodelcreatedinLabVIEW.



Example:Simulation
BelowweseeanexampleofasimulationmodelusingtheControlandSimulationLoop.


Noticethefollowing:
Tutorial: Control and Simulation in LabVIEW

18



Simulation

Clickontheborderofthesimulationloopandselect“ConfigureSimulationParameters…”


Thefollowingwindowappears(ConfigureSimulationParameters):


InthiswindowyousetsomeParametersregardingthesimulation,someimportantare:
•
•

FinalTime(s)–sethowlongthesimulationshouldlast.Foraninfinitetimeset“Inf”.
EnableSynchronizedTiming-Specifiesthatyouwanttosynchronizethetimingof
theControl&SimulationLooptoatimingsource.Toenablesynchronization,placea
Tutorial: Control and Simulation in LabVIEW




19

Simulation

checkmarkinthischeckboxandthenchooseatimingsourcefromtheSourcetype
listbox.
ClicktheHelpbuttonformoredetails.
YoumayalsosetsomeoftheseParametersintheBlockDiagram:


YoumayusethemousetoincreasethenumbersofParametersandright-clickandselect
“SelectInput”.

Exercises
Exercise:Simulationofaspring-massdampersystem
Inthisexerciseyouwillconstructasimulationdiagramthatrepresentsthebehaviorofa
dynamicsystem.Youwillsimulateaspring-massdampersystem.
𝐹(𝑡) − 𝑐𝑥(𝑡) − 𝑘𝑥(𝑡) = 𝑚𝑥(𝑡)
wheretisthesimulationtime,F(t)isanexternalforceappliedtothesystem,cisthe
dampingconstantofthespring,kisthestiffnessofthespring,misamass,andx(t)isthe
positionofthemass. 𝑥 isthefirstderivativeoftheposition,whichequalsthevelocityof
themass. 𝑥 isthesecondderivativeoftheposition,whichequalstheaccelerationofthe
mass.
Thefollowingfigureshowsthisdynamicsystem.



Tutorial: Control and Simulation in LabVIEW


20

Simulation


Thegoalistoviewthepositionx(t)ofthemassmwithrespecttotimet.Youcancalculate
thepositionbyintegratingthevelocityofthemass.Youcancalculatethevelocityby
integratingtheaccelerationofthemass.Ifyouknowtheforceandmass,youcancalculate
thisaccelerationbyusingNewton'sSecondLawofMotion,givenbythefollowingequation:
Force=Mass×Acceleration
Therefore,
Acceleration=Force/Mass
Substitutingtermsfromthedifferentialequationaboveyieldsthefollowingequation:
𝑥=

1
(𝐹 − 𝑐𝑥 − 𝑘𝑥)
𝑚

Youwillconstructasimulationdiagramthatiteratesthefollowingstepsoveraperiodof
time.
CreatingtheSimulationDiagram
YoucreateasimulationdiagrambyplacingaControl&SimulationLoopontheLabVIEW
blockdiagram.
1. LaunchLabVIEWandselectFile»NewVItocreateanew,blankVI.
2. SelectWindow»ShowBlockDiagramtoviewtheblockdiagram.Youalsocanpress
the<Ctrl-E>keystoviewtheblockdiagram.
3. IfyouarenotalreadyviewingtheFunctionspalette,selectView»FunctionsPaletteto
displaythispalette.
4. SelectControlDesign&Simulation»SimulationtoviewtheSimulationpalette.

5. ClicktheControl&SimulationLoopicon.
6. Movethecursorovertheblockdiagram.Clicktoplacethetopleftcorneroftheloop,
dragthecursordiagonallytoestablishthesizeoftheloop,andclickagaintoplace
theloopontheblockdiagram.
ThesimulationdiagramistheareaenclosedbytheControl&SimulationLoop.Noticethe
simulationdiagramhasapaleyellowbackgroundtodistinguishitfromtherestoftheblock
diagram.YoucanresizetheControl&SimulationLoopbydraggingitsborders.
ConfiguringSimulationParameters
TheControl&SimulationLoopcontainstheparametersthatdefinehowthesimulation
executes.Completethefollowingstepstoviewandconfigurethesesimulationparameters.
1. Double-clicktheInputNode,attachedtotheleftsideoftheControl&Simulation
Loop,todisplaytheConfigureSimulationParametersdialogbox.YoualsocanrightTutorial: Control and Simulation in LabVIEW