《水處理技術(shù)（雙語）》課件-PID控制知識

PIDcontrolknowledgePID控制知識PID簡介IntroductiontoPID比例積分微分控制，簡稱PID控制，是最早發(fā)展起來的控制策略之一，由于其算法簡單和可靠性高，被廣泛應(yīng)用于工業(yè)過程控制，至今仍有90%左右的控制回路具有PID結(jié)構(gòu)。PID控制，實際中也有PI和PD控制。PID控制器就是根據(jù)系統(tǒng)的誤差，利用比例、積分、微分計算出控制量進(jìn)行控制的。從信號變換的角度而言，超前校正、滯后校正、滯后－超前校正可以總結(jié)為比例、積分、微分三種運算及其組合。Proportionalintegraldifferentialcontrol,orPIDcontrolforshort,isoneoftheearliestcontrolstrategiesdeveloped,andiswidelyusedinindustrialprocesscontrolduetoitssimplealgorithmandhighreliability,andstillhasaPIDstructureinabout90%ofcontrolloops.pidcontrol,inpractice,alsohasPIandPDcontrol.PIDcontrollersarethosethatuseproportional,integralanddifferentialcalculationstocontrolthecontrolquantitiesaccordingtotheerrorofthesystem.Fromthepointofviewofsignaltransformation,overruncorrection,lagcorrectionandlag-overruncorrectioncanbesummarisedasproportional,integralanddifferentialoperationsandtheircombinations.比例環(huán)節(jié)：即時成比例地反應(yīng)控制系統(tǒng)的偏差信號e(t)。

Proportionallink:instantproportionalresponsetothedeviationsignale(t)ofthecontrolsystem.積分環(huán)節(jié)：能對誤差進(jìn)行記憶，主要用于消除靜差，提高系統(tǒng)的無差度。Integrallink:enablesthememoryoferrors,mainlyforeliminatingstaticdifferencesandimprovingthenon-differentiationofthesystem.微分環(huán)節(jié)：能反映偏差信號的變化趨勢(變化速率)，并能在偏差信號值變得太大之前，在系統(tǒng)中引入一個有效的早期修正信號，從而加快系統(tǒng)的動作速度，減小調(diào)節(jié)時間。Differentiallink:reflectsthetrend(rateofchange)ofthedeviationsignalandintroducesaneffectiveearlycorrectionsignalinthesystembeforethevalueofthedeviationsignalbecomestoolarge,thusspeedinguptheactionofthesystemandreducingtheadjustmenttimePID控制器各校正環(huán)節(jié)的作用TheroleofeachcorrectionlinkofthePIDcontrollerPID控制器的參數(shù)整定是控制系統(tǒng)設(shè)計的核心內(nèi)容。TheparameteradjustmentofthePIDcontrolleristhecoreelementofthecontrolsystemdesign.它是根據(jù)被控過程的特性確定PID控制器的比例系數(shù)、積分時間和微分時間的大小。Itisbasedonthecharacteristicsofthecontrolledprocesstodeterminethesizeofthescalefactor,integrationtimeanddifferentiationtimeofthePIDcontroller.PID參數(shù)的整定方法

MethodofadjustingPIDparameters它主要是依據(jù)系統(tǒng)的數(shù)學(xué)模型，經(jīng)過理論計算確定控制器參數(shù)。Itismainlybasedonthemathematicalmodelofthesystem,aftertheoreticalcalculationstodeterminethecontrollerparameters.這種方法所得到的計算數(shù)據(jù)未必可以直接用，還必須通過工程實際進(jìn)行調(diào)整和修改。Thecalculationdataobtainedbythismethodmaynotbeuseddirectly,butmustalsobeadjustedandmodifiedbyengineeringpractice.PID控制器參數(shù)整定PIDcontrollerparameteradjustment（1）理論計算整定法

TheoreticalcalculationandadjustmentmethodPID控制器參數(shù)整定PIDcontrollerparameteradjustment（2）工程整定方法Engineeringcalibrationmethods它主要依賴工程經(jīng)驗，直接在控制系統(tǒng)的試驗中進(jìn)行，且方法簡單、易于掌握，在工程實際中被廣泛采用。Itreliesheavilyonengineeringexperience,directlyinthetestingofcontrolsystems,andthemethodissimpleandeasytomasterandiswidelyusedinengineeringpractice.PID控制器參數(shù)的工程整定方法，主要有臨界比例法、反應(yīng)曲線法和衰減法。ThemainengineeringmethodsfortheadjustmentofPIDcontrollerparametersarethecriticalproportionmethod,theresponsecurvemethodandthedecaymethod.三種方法各有其特點，其共同點都是通過試驗，然后按照工程經(jīng)驗公式對控制器參數(shù)進(jìn)行整定。Eachofthethreemethodshasitsowncharacteristics,buttheyallhaveincommonthatthecontrollerparametersareadjustedthroughtestsandthenaccordingtoempiricalengineeringformulas.都需要在實際運行中進(jìn)行最后調(diào)整與完善。Allrequirefinaladjustmentandrefinementinactualoperation.現(xiàn)在一般采用的是臨界比例法。Thecriticalproportionmethodisnowgenerallyused.工業(yè)方面IndustrialA首先預(yù)選擇一個足夠短的采樣周期讓系統(tǒng)工作；Firstpre-selectashortenoughsamplingperiodtoallowthesystemtooperate.B僅加入比例控制環(huán)節(jié)，直到系統(tǒng)對輸入的階躍響應(yīng)出現(xiàn)臨界振蕩，記下這時的比例放大系數(shù)和臨界振蕩周期；Addonlytheproportionalcontrollinkuntilacriticaloscillationinthestepresponseofthesystemtotheinputoccurs,notingtheproportionalamplificationfactorandthecriticaloscillationperiodatthispoint.

C在一定的控制度下通過公式計算得到PID控制器的參數(shù)。TheparametersofthePIDcontrollerareobtainedbyequationatacertaindegreeofcontrol.D系統(tǒng)空載、帶載聯(lián)調(diào)，再對PID參數(shù)進(jìn)行微調(diào)，直至滿足要求。偏差越大，積分越慢；反之則越快。Thesystemisjointlyadjustedwithnoloadandload,andthenthePIDparametersareslightlyadjusteduntiltherequirementsaremet.Thegreaterthedeviation,theslowertheintegration;Onthecontrary,thefaster.整定步驟如下：Therectificationstepsareasfollows.

PID調(diào)試一般步驟GeneralstepsforPIDcommissioning（1）確定比例增益PDeterminetheproportionalgainP首先去掉PID的積分項和微分項，一般是令Ti=0、Td=0（具體見PID的參數(shù)設(shè)定說明），使PID為純比例調(diào)節(jié)。輸入設(shè)定為系統(tǒng)允許的最大值的60%~70%，由0逐漸加大比例增益P，直至系統(tǒng)出現(xiàn)振蕩；TheintegralanddifferentialtermsofthePIDarefirstremoved,generallybymakingTi=0andTd=0(seethePIDparametersettinginstructionsfordetails),makingthePIDpurelyproportional.Theinputissetto60%to70%ofthemaximumallowedforthesystemandtheproportionalgainPisgraduallyincreasedfrom0untilthesystemoscillates.再反過來，從此時的比例增益P逐漸減小，直至系統(tǒng)振蕩消失，記錄此時的比例增益P，設(shè)定PID的比例增益P為當(dāng)前值的60%~70%。比例增益P調(diào)試完成。Theninturn,graduallyreducetheproportionalgainPfromthispointuntilthesystemoscillationdisappears,recordtheproportionalgainPatthispoint,andsettheproportionalgainPofthePIDto60%~70%ofthecurrentvalue.ProportionalgainPcommissioningiscompleted.PID調(diào)試一般步驟GeneralstepsforPIDcommissioning（2）確定積分時間常數(shù)TiDeterminingtheintegrationtimeconstantTi

比例增益P確定后，設(shè)定一個較大的積分時間常數(shù)Ti的初值。AftertheproportionalgainPhasbeendetermined,setaninitialvalueofTiforalargeintegrationtimeconstant.然后逐漸減小Ti，直至系統(tǒng)出現(xiàn)振蕩，之后在反過來，逐漸加大Ti，直至系統(tǒng)振蕩消失。ThengraduallyreduceTiuntilthesystemoscillates,afterwhichinturn,graduallyincreaseTiuntilthesystemoscillationdisappears.記錄此時的Ti，設(shè)定PID的積分時間常數(shù)Ti為當(dāng)前值的150%~180%。積分時間常數(shù)Ti調(diào)試完成。RecordtheTiatthispointandsettheintegrationtimeconstantTiofthePIDto150%~180%ofthecurrentvalue.TheintegrationtimeconstantTicommissioningiscompleted.010203微分時間常數(shù)Td一般不用設(shè)定，為0即可。若要設(shè)定，與確定P和Ti的方法相同，取不振蕩時的30%。ThedifferentialtimeconstantTddoesnotnormallyneedtobeset,butissimply0.Ifitistobeset,itisdeterminedinthesamewayasPandTi,bytaking30%ofthevaluewhennotoscillating.PID調(diào)試一般步驟GeneralstepsforPIDcommissioning（3）確定微分時間常數(shù)TdDeterminethedifferentialtimeconstantTd各個環(huán)節(jié)特點Individualsessioncharacteristics（1）比例環(huán)節(jié)ProportionallinksP參數(shù)越小比例作用越強(qiáng)，動態(tài)響應(yīng)越快，消除誤差的能力越強(qiáng)。但實際系統(tǒng)是有慣性的，控制輸出變化后，實際值y(t)變化還需等待一段時間才會緩慢變化。ThesmallerthePparameterthestrongertheproportionaleffect,thefasterthedynamicresponseandthegreatertheabilitytoeliminateerrors.However,theactualsystemisinertialandtheactualvalueofy(t)changesafterthecontroloutputhaschangedandhastowaitforsometimebeforeitchangesslowly.由于實際系統(tǒng)是有慣性的，比例作用不宜太強(qiáng)，比例作用太強(qiáng)會引起系統(tǒng)振蕩不穩(wěn)定。P參數(shù)的大小應(yīng)在以上定量計算的基礎(chǔ)上根據(jù)系統(tǒng)響應(yīng)情況，現(xiàn)場調(diào)試決定，通常將P參數(shù)由大向小調(diào)，以能達(dá)到最快響應(yīng)又無超調(diào)(或無大的超調(diào))為最佳參數(shù)。Astheactualsystemisinertial,theproportionaleffectshouldnotbetoostrong,theproportionaleffectistoostrongwillcausesystemoscillationinstability.thesizeofthePparametershouldbebasedontheabovequantitativecalculationofthesystemresponse,fieldcommissioningdecision,usuallythePparameterfromlargetosmalladjustment,toachievethefastestresponseandnoovershoot(ornolargeovershoot)forthebestparameters.各個環(huán)節(jié)特點Individualsessioncharacteristics優(yōu)點:調(diào)整系統(tǒng)的開環(huán)比例系數(shù)，提高系統(tǒng)的穩(wěn)態(tài)精度，減低系統(tǒng)的惰性，加快響應(yīng)速度。Advantages:Adjuststheopen-loopscalefactorofthesystem,improvesthesteady-stateaccuracyofthesystem,reducestheinertiaofthesystemandspeedsuptheresponsetime.Disadvantages:WiththePcontrolleronly,anoversizedopen-loopproportionalityfactorwillnotonlyincreasetheovershootofthesystem,butwillalsomakethesystemstabilitymarginsmaller,orevenunstable.缺點:僅用P控制器,過大的開環(huán)比例系數(shù)不僅會使系統(tǒng)的超調(diào)量增大，而且會使系統(tǒng)穩(wěn)定裕度變小，甚至不穩(wěn)定。各個環(huán)節(jié)特點Individualsessioncharacteristics（2）積分環(huán)節(jié)PointsSession控制器的輸出與輸入誤差信號的積分成正比關(guān)系。主要用于消除靜差，提高系統(tǒng)的無差度。Theoutputofthecontrollerisproportionaltotheintegrationoftheinputerrorsignal.Itismainlyusedtoeliminatestaticdifferencesandimprovethenon-differentiationofthesystem.積分作用的強(qiáng)弱取決于積分時間常數(shù)T,T越大，積分作用越弱，反之則越強(qiáng)。ThestrengthoftheintegralactiondependsontheintegrationtimeconstantT,thelargertheT,theweakertheintegralactionandviceversa.各個環(huán)節(jié)特點Individualsessioncharacteristics869,7k優(yōu)點：消除穩(wěn)態(tài)誤差

Advantage:Eliminationofsteady-stateerrors.缺點：積分控制器的加入會影響系統(tǒng)的穩(wěn)定性，使系統(tǒng)的穩(wěn)定裕度減小。Disadvantage:Theinclusionofanintegralcontrolleraffectsthestabilityofthesystemandreducesthestabilitymarginofthesystem.各個環(huán)節(jié)特點Individualsessioncharacteristics（3）微分環(huán)節(jié)Differentiallinks反映偏差信號的變化趨勢，并能在偏差信號變得太大之前，在系統(tǒng)中引入一個有效的早期修正信號，從而加快系統(tǒng)的動作速度，減少調(diào)節(jié)時間。在微分控制中，控制器的輸出與輸入誤差信號的微分（即誤差的變化率）成正比關(guān)系。Reflectsthetrendofthedeviationsignalandcanintroduceaneffectiveearlycorrectionsignalintothesystembeforethedeviationsignalbecomestoolarge,thusspeedingupthesystem'sactionandreducingregulationtime.Indifferentialcontrol,theoutputofthecontrollerisproportionaltothedifferentialoftheinputerrorsignal(i.e.therateofchangeofthe