运用PID控制英文文献.docx

运用PID控制英文文献.docx

《运用PID控制英文文献.docx》由会员分享，可在线阅读，更多相关《运用PID控制英文文献.docx（27页珍藏版）》请在冰豆网上搜索。

运用PID控制英文文献

ApplicationNote83402

OriginalInstructions

PIDControl

WoodwardwishestothankandacknowledgeE.I.DuPontDeNemours&Company,Inc.forgranting

permissiontouseinformationpresentedinDuPont'sELIASInstrumentationTrainingProgrambookletinthis

Woodwardpublication.DuPont'scopyrighttotheabovementiondocumentisasfollows:

Copyright（1970）E.I.DuPontDeNemours&Company,Inc.

[WrittenbyLarryMcLeister]

WoodwardGovernorCompanyreservestherighttoupdateanyportionofthispublicationatanytime.Informationprovided

byWoodwardGovernorCompanyisbelievedtobecorrectandreliable.However,noresponsibilityisassumedbyWoodward

GovernorCompanyunlessotherwiseexpresslyundertaken.

©Woodward1992

AllRightsReserved

ApplicationNote83402PIDControl

Woodward1

Contents

CHAPTER1.INTRODUCTION.........................................................................2

ProcessControlLoop.............................................................................................2

AutomaticControl...................................................................................................3

ControlLoop...........................................................................................................4

ControlModes........................................................................................................4

ControlModes（CarAnalogy）.................................................................................5

ProportionalControl................................................................................................5

Integral（Reset）.......................................................................................................5

Derivative（PreactandRateTime）.........................................................................5

ControlResponses.................................................................................................6

CHAPTER2.SINGLE-MODECONTROL.........................................................7

On-OffControl........................................................................................................7

ProportionalResponse...........................................................................................9

ProportionalGain（EffectofSettings）.....................................................................9

Chapter2Summary.............................................................................................10

Chapter2ReviewQuestions................................................................................10

CHAPTER3.INTEGRALANDDERIVATIVECONTROL....................................11

Proportional+Integral（OpenLoop）.....................................................................11

Integral..................................................................................................................12

Proportional+Integral（ClosedLoop）..................................................................13

Integral（EffectsofSettings）.................................................................................14

DerivativeResponse............................................................................................15

Derivative（Minutes）..............................................................................................16

Proportional+Derivative（ClosedLoop）..............................................................17

Derivative（EffectsofSettings）.............................................................................18

Proportional+Integral+Derivative（ClosedLoop）..............................................19

Chapter3Summary.............................................................................................19

Chapter3Review.................................................................................................20

CHAPTER4.TUNINGGUIDELINES..............................................................22

ControllerTuningMethodSample........................................................................24

ControllerFieldTuningGeneral...........................................................................25

ControllerFieldTuningProcedure.......................................................................27

PIDControlApplicationNote83402

2Woodward

Chapter1.

Introduction

ProcessControlLoop

Withthisblockdiagramofacontrolloop,thefollowingcanbeshown:

Thedashessurroundingthemeasurementtransmitter,thecontrolstation,and

thecontrollerindicatethe"local"controlstationsinceallpartsarewithinone

case.

Thedashessurroundingthecontrolstationandcontrolleronlyindicatethe

"remote"controlstation.

Thecontrollerinthiscasemaybemountedoneofthreeways:

onthecontrolstation

behindthecontrolpanelonarackwithothercontrollers

inthefieldonornearthecontrolvalve.

Itmayalsobeanintegralpartofthecontrolstationastheoneusedinthetraining

setup.

Bothtypesofcontrolstationswillhavesomewayofindicating（orrecording）the

processvariable,somemeansforadjustingthedesiredsetpoint,andameansfor

readingthecontrolleroutputtothecontrolvalve.The"local"controlstationmayor

maynothaveameansfor"manually"controllingthecontrolvalve.The"remote"

willalwayshavethisfacility.The"local"controlstationrequiresfrequentvisitation

todeterminequalityofcontrol.The"remote"stationiscentrallylocated,therefore

reducingtraveltimeandallowingside-by-sidecontrolqualityscanning.

ApplicationNote83402PIDControl

Woodward3

Thefunctionofeachblockofthediagramisasfollows:

1.Measurementtransmitter—measurestheprocessvariable（temperature,

pressure,level,flow,oranalysis）andconvertsthemeasurementtounits

usefultothecontroller（psig,kPa,etc）orsomeelectronicvaluesuchas4–20

mA.

2.Thecontrolstationprovidesfacilityforsettingthedesiredcontrolpoint,

readingthevalueofthemeasurement,transferringtheoperationfrommanual

toautomaticorautomatictomanual,andallowsmanualloadingofthecontrol

valve.

3.Thecontrollertakesthesetpointvalueofthecontrolstation,comparesits

valuetothemeasurementandreactstothedifferenceaccordingtothevalues

setoneachresponse,proportional,resetandderivative.

4.Theoutputsignalfromthecontrollerpositionsthecontrolvalve.

5.Theprocesschangesresultingfromthevalvechangesarefeltbythe

measurementandtheprocedurecontinues.

AutomaticControl

Thischartisasimplifiedformofthepreviouschart.Therearethreethingsthattake

place:

measurement

decision

action

Measurement,ofcourse,istheprocessvariabletobecontrolled.

Thedecisionisthecontroller.

Theactionisthecontrolvalve,sometimescalledthefinalelement.

Notethatthearrowsflowcontinuouslyasdoesthefunctionofanyclosedloop

controlsystem.Allsectionsofthecontrolsystemarecontinuouslyconnected,even

thoughactiondoesnottakeplaceunlessachangetakesplacethatresultsinthe

processvariablemeasureddeviatingfromthesetpoint（desiredcontrolpoint）.

PIDControlApplicationNote83402

4Woodward

Tobreaktheconnectionbetweenanysectionoftheloopwouldresultinanopen

loopconfiguration.Ofcourse,theprocesswillthennotrespondtocontrolleraction.

However,aslaterchartswillshow,openloopconfigurationisauniquewayof

observingcontrolleractionsorresponsesonanindividualbasisandwithoutthe

interferingprocessresponse.

ControlLoop

Measurement（Transmitter）

1.Temperature

2.Pressure

3.Level

4.Flow

5.X-Analysis

Decision（Controller）

1.Setpointvs.measurement

2.Controllerresponse

Action（FinalElement）

1.Controlvalve

2.Pump

3.Rheostat

Controlloopcomponentsconsistofthoseshownontheabovechart.Asmentioned

earlier,threethingstakeplaceinaclosedloopcontrolsystem—Measurement,

Decision,Action,wheneverthesystemisinautomatic.Themeasurementsection

isconnecteddirectlytotheprocessandtransmitsthevariabletobecontrolledto

thecontrolstation,usuallysomedistanceaway.Thecontrolstation,which

technicallyincludesthecontroller,allowscomparisonbetweenthedesiredcontrol

point（setpoint）andthemeasuredcontrolpoint.Theamountofthedeviation,the

rateofthedeviationandthedurationofthedeviationallpredictcontrollerresponse

accordingtothecontroller'sgain,derivativeandresetsettings.

Theactionissimplytheresultofthecontrolleroutput.Itmaybesomethingother

thanacontrolvalve.

ControlModes

On-OffOr（Deadband）

Proportionalor（Prop_Gn）

Integralor（Int_Gn）

Derivativeor（S_D_R）

Asmentionedearlier,modesofcontrolrefertothevarioustypesofcontrol

available.Alsoitmustberememberedthatthetypeofcontrolshouldmatchthe

process.Forexample,on-offcontrolisquiteadequateforhomeheatingsystems,

butwouldbeveryunsatisfactoryinmostpetroleum/chemicalapplicationsbecause

ofitscycliccharacteristic.

Proportionalcontroleliminatesthecycliccharacteristicsoftheon-offmode.

IntegralandDerivativearerefinementsofandworkinconjunctionwithproportional

control.Specialstudiesofeachfollow.

ApplicationNote83402PIDControl

Woodward5

ControlModes（CarAnalogy）

ON-OFF—Onespeedwindshieldwiperinlightrain.

Onewaytodescribetermsnormallyunfamiliaristodrawananalogytosomething

whichisfamiliar.

TheanalogyhereforOn-Offcontrolisturningthewindshieldwiper"on"then"off".

Itsspeedisnotchanged.Itissimplyturned"on"foronewipe,thenturnedoff.

A