中英文文献翻译PID控制器.docx
- 文档编号:22911349
- 上传时间:2023-04-29
- 格式:DOCX
- 页数:21
- 大小:31.71KB
中英文文献翻译PID控制器.docx
《中英文文献翻译PID控制器.docx》由会员分享,可在线阅读,更多相关《中英文文献翻译PID控制器.docx(21页珍藏版)》请在冰豆网上搜索。
中英文文献翻译PID控制器
附件1:
外文原文
PIDcontroller
ZuoXinandSunJinming
(ResearchInstituteofAutomation.UniversityofPetroleum,Belting102249,China)
ReceivedApril2,2005
Abstract:
Performaneeassessmentofaproportional-integral-derivative(PID)controllerisconduetedusingthePIDachievableminimumvarianeeasabenchmarkWhentheprocessmodelisunknownwecarlestimatetheP^D-achievableminimumvarianeeandthecorrespondingparametersbyroutineclosed-loopoperationdataSimulationresultsshowthattheprocessoutputvarianeeisreducedbyretuningcontrollerparameters
Keywords:
PerformaneeassessmentPIDcontrol,minimumvarianee
Aproportional-ntegral-derivativeeontroller(PIDeontroller)isageneric.controlloopfeedbackmechanismwidelyusedinindustrialeontrolsystems.APIDeontrollerattemptstocorrecttheerrorbetweenameasuredprocessvariableandadesiredsetpointbycalculatingandthenoutputtingacorrectiveactionthatcanadjusttheprocessaccordingly.
ThePIDeontrollercalculation(algorithm)invoIvesthreeseparateparameters;theProportional,theIntegralandDerivativevalues.TheProportionalvaluedeterminesthereactiontothecurrenterror,theIntegraldeterminesthereactionbasedonthesumofrecenterrorsandtheDerivativedeterminesthereactiontotherateatwhichtheerrorhasbeenchanging.Theweightedsumofthesethreeactionsisusedtoadjusttheprocessviaaeontrolelementsuchasthepositionofaeontrolvalveorthepowersupplyofaheatingelement.By"tuning"thethreeeonstantsinthePIDeontrolleralgorithmthePIDcanprovideeontrolactiondesignedforspecificprocessrequirements.Theresponseoftheeontrollercanbedescribedintermsoftheresponsivenessoftheeontrollertoanerror,thedegreetowhichtheeontrollerovershootsthesetpointandthedegreeofsystemoscillation.NotethattheuseofthePIDalgorithmforeontroldoesnotguaranteeoptimaleontrolofthesystemorsystemstability.
Someapplicationsmayrequireusingonlyoneortwomodestoprovidetheappropriatesystemcontrol.Thisisachievedbysettingthegainofundesiredcontroloutputstozero.APIDcontrollerwillbecalledaPI,PD,PorIcontrollerintheabseneeoftherespectivecontrolactions.PIcontrollersareparticularlycommon,sincederivativeactionisverysensitivetomeasurementnoise,andtheabsenceofanintegralvaluemaypreventthesystemfromreachingitstargetvalueduetothecontrolaction.
Note:
Duetothediversityofthefieldofcontroltheoryandapplication,manynamingconventionsfortherelevantvariablesareincommonuse.
1.Controlloopbasics
Afamiliarexampleofacontrolloopistheactiontakentokeepone'sshowerwaterattheidealtemperature,whichtypicallyinvoIvesthemixingoftwoprocessstreams,coldandhotwater.Thepersonfeelsthewatertoestimateitstemperature.Basedonthismeasurementtheyperformacontrolaction:
usethecoldwatertaptoadjusttheprocess.Thepersonwouldrepeatthisinput-outputcontrolloop,adjustingthehotwaterflowuntiltheprocesstemperaturestabilizedatthedesiredvalue.
Feelingthewatertemperatureistakingameasurementoftheprocessvalueorprocessvariable(PV).Thedesiredtemperatureiscalledthesetpoint(SP).Theoutputfromthecontrollerandinputtotheprocess(thetapposition)iscalledthemanipulatedvariable(MV).Thedifferencebetweenthemeasurementandthesetpointistheerror(e),toohotortoocoldandbyhowmuch.Asacontroller,onedecidesroughlyhowmuchtochangethetapposition(MV)afteronedeterminesthetemperature(PV),andthereforetheerror.ThisfirstestimateistheequivalentoftheproportionalactionofaPIDcontroller.TheintegralactionofaPIDcontrollercanbethoughtofasgraduallyadjustingthetemperaturewhenitisalmostright.Derivativeactioncanbethoughtofasnoticingthewatertemperatureisgettinghotterorcolder,andhowfast,andtakingthatintoaccountwhendecidinghowtoadjustthetap.Makingachangethatistoolargewhentheerrorissmallisequivalenttoahighgaincontrollerandwillleadtoovershoot.Ifthecontrollerweretorepeatedlymakechangesthatweretoolargeandrepeatedlyovershootthetarget,thiscontrolloopwouldbetermedunstableandtheoutputwouldoscillatearoundthesetpointineitheraconstant,growing,ordecayingsinusoid.Ahumanwouldnotdothisbecauseweareadaptivecontrollers,learningfromtheprocesshistory,butPIDcontrollersdonothavetheabilitytolearnandmustbesetupcorrectly.Selectingthecorrectgainsforeffectivecontrolisknownastuningthecontroller.
Ifacontrollerstartsfromastablestateatzeroerror(PV=SP),thenfurtherchangesbythecontrollerwillbeinresponsetochangesinothermeasuredorunmeasuredinputstotheprocessthatimpactontheprocess,andhenceonthePV.VariablesthatimpactontheprocessotherthantheMVareknownasdisturbancesandgenerallycontrollersareusedtorejectdisturbancesand/orimplementsetpointchanges.Changesinfeedwatertemperatureconstituteadisturbaneetotheshowerprocess.
Intheory,acontrollercanbeusedtocontrolanyprocesswhichhasameasurableoutput(PV),aknownidealvalueforthatoutput(SP)andaninputtotheprocess(MV)thatwillaffecttherelevantPV.Controllersareusedinindustrytoregulatetemperature,pressure,flowrate,chemicalcomposition,speedandpracticallyeveryothervariableforwhichameasurementexists.Automobilecruisecontrolisanexampleofaprocesswhichutilizesautomatedcontrol.
Duetotheirlonghistory,simplicity,wellgroundedtheoryandsimplesetupandmaintenancerequirements,PIDcontrollersarethecontrollersofchoiceformanyoftheseapplications.
2.PIDcontrollertheory
Note:
Thissectiondescribestheidealparallelornon-interactingformofthePIDcontroller.ForotherformspleaseseetheSection"AlternativenotationandPIDforms".
ThePIDcontrolschemeisnamedafteritsthreecorrectingterms,whosesumconstitutesthemanipulatedvariable(MV).Hence:
MV(t)=Pout+/out+Dout.
WherePout,lout,andDoutarethecontributionstotheoutputfromthePIDcontrollerfromeachofthethreeterms,asdefinedbelow.
2.1.Proportionalterm
Theproportionaltermmakesachangetotheoutputthatisproportionaltothecurrenterrorvalue.TheproportionalresponsecanbeadjustedbymultiplyingtheerrorbyaconstantKp,calledtheproportionalgain.
Theproportionaltermisgivenby:
H>ut=Ape(f)
Where
Pout:
Proportionaloutput
Kp:
ProportionalGain,atuningparameter
e:
Error=SP-PV
t:
Timeorinstantaneoustime(thepresent)
ChangeofresponseforvaryingKpAhighproportionalgainresultsinalargechangeintheoutputforagivenchangeintheerror.Iftheproportionalgainistoohigh,thesystemcanbecomeunstable(SeethesectiononLoopTuning).Incontrast,asmallgainresultsinasmalloutputresponsetoalargeinputerror,andalessresponsive(orsensitive)controller.Iftheproportionalgainistoolow,thecontrolactionmaybetoosmallwhenrespondingtosystemdisturbances.
Intheabsenceofdisturbances,pureproportionalcontrolwillnotsettleatitstargetvalue,butwillretainasteadystateerrorthatisafunctionoftheproportionalgainandtheprocessgain.Despitethesteady-stateoffset,bothtuningtheoryandindustrialpracticeindicatethatitistheproportionaltermthatshouldcontributethebulkoftheoutputchange.
2.2.Integralterm
Thecontributionfromtheintegraltermisproportionaltoboththemagnitudeoftheerrorandthedurationoftheerror.Summingtheinstantaneouserrorovertime(integratingtheerror)givestheaccumulatedoffsetthatshouldhavebeencorrectedpreviously.Theaccumulatederroristhenmultipliedbytheintegralgainandaddedtothecontrolleroutput.Themagnitudeofthecontributionoftheintegraltermtotheoverallcontrolactionisdeterminedbytheintegralgain,Ki.
Theintegraltermisgivenby:
/out=A'ie(r)dr
Jo
Iout:
Integraloutput
Ki:
IntegralGain,atuningparameter
e:
Error=SP-PV
t:
Timeinthepastcontributingtotheintegralresponse
Theintegralterm(whenaddedtotheproportionalterm)acceleratesthemovementoftheprocesstowardssetpointandeliminatestheresidualsteady-stateerrorthatoccurswithaproportionalonlycontroller.However,sincetheintegraltermisrespondingtoaccumulatederrorsfromthepast,itcancausethepresentvaluetoovershootthesetpointvalue(crossoverthesetpointandthencreateadeviationintheotherdirection).Forfurthernotesregardingintegralgaintuningandcontrollerstability,seethesectiononlooptuning.
2.3Derivativeterm
Therateofchangeoftheprocesserroriscalculatedbydeterminingtheslopeoftheerrorovertime(i.e.itsfirstderivativewithrespecttotime)andmultiplyingthisrateofchangebythederivativegainKd.Themagnitudeofthecontributionofthederivativetermtotheoverallcontrolactionistermedthederivativegain,Kd.
Thederivativetermisgivenby:
Omit=K(i—
Dout:
Derivativeoutput
Kd:
DerivativeGain,atuningparameter
e:
Error=SP-PV
t:
Timeorinstantaneoustime(thepresent)
Thederivativetermslowstherateofchangeofthecontrolleroutputandthiseffectismostnoticeableclosetothecontrollersetpoint.Hence,derivativecontrolisusedtoreducethemagnitudeoftheovershootproducedbytheintegralcomponentandimprovethecombinedcontroller-processstability.However,differentiationofasignalamplifiesnois
- 配套讲稿:
如PPT文件的首页显示word图标,表示该PPT已包含配套word讲稿。双击word图标可打开word文档。
- 特殊限制:
部分文档作品中含有的国旗、国徽等图片,仅作为作品整体效果示例展示,禁止商用。设计者仅对作品中独创性部分享有著作权。
- 关 键 词:
- 中英文 文献 翻译 PID 控制器