《水处理技术（双语）》课件-PID控制知识

PIDcontrolknowledgePID控制知识PID简介IntroductiontoPID比例积分微分控制，简称PID控制，是最早发展起来的控制策略之一，由于其算法简单和可靠性高，被广泛应用于工业过程控制，至今仍有90%左右的控制回路具有PID结构。PID控制，实际中也有PI和PD控制。PID控制器就是根据系统的误差，利用比例、积分、微分计算出控制量进行控制的。从信号变换的角度而言，超前校正、滞后校正、滞后－超前校正可以总结为比例、积分、微分三种运算及其组合。Proportionalintegraldifferentialcontrol,orPIDcontrolforshort,isoneoftheearliestcontrolstrategiesdeveloped,andiswidelyusedinindustrialprocesscontrolduetoitssimplealgorithmandhighreliability,andstillhasaPIDstructureinabout90%ofcontrolloops.pidcontrol,inpractice,alsohasPIandPDcontrol.PIDcontrollersarethosethatuseproportional,integralanddifferentialcalculationstocontrolthecontrolquantitiesaccordingtotheerrorofthesystem.Fromthepointofviewofsignaltransformation,overruncorrection,lagcorrectionandlag-overruncorrectioncanbesummarisedasproportional,integralanddifferentialoperationsandtheircombinations.比例环节：即时成比例地反应控制系统的偏差信号e(t)。

Proportionallink:instantproportionalresponsetothedeviationsignale(t)ofthecontrolsystem.积分环节：能对误差进行记忆，主要用于消除静差，提高系统的无差度。Integrallink:enablesthememoryoferrors,mainlyforeliminatingstaticdifferencesandimprovingthenon-differentiationofthesystem.微分环节：能反映偏差信号的变化趋势(变化速率)，并能在偏差信号值变得太大之前，在系统中引入一个有效的早期修正信号，从而加快系统的动作速度，减小调节时间。Differentiallink:reflectsthetrend(rateofchange)ofthedeviationsignalandintroducesaneffectiveearlycorrectionsignalinthesystembeforethevalueofthedeviationsignalbecomestoolarge,thusspeedinguptheactionofthesystemandreducingtheadjustmenttimePID控制器各校正环节的作用TheroleofeachcorrectionlinkofthePIDcontrollerPID控制器的参数整定是控制系统设计的核心内容。TheparameteradjustmentofthePIDcontrolleristhecoreelementofthecontrolsystemdesign.它是根据被控过程的特性确定PID控制器的比例系数、积分时间和微分时间的大小。Itisbasedonthecharacteristicsofthecontrolledprocesstodeterminethesizeofthescalefactor,integrationtimeanddifferentiationtimeofthePIDcontroller.PID参数的整定方法

MethodofadjustingPIDparameters它主要是依据系统的数学模型，经过理论计算确定控制器参数。Itismainlybasedonthemathematicalmodelofthesystem,aftertheoreticalcalculationstodeterminethecontrollerparameters.这种方法所得到的计算数据未必可以直接用，还必须通过工程实际进行调整和修改。Thecalculationdataobtainedbythismethodmaynotbeuseddirectly,butmustalsobeadjustedandmodifiedbyengineeringpractice.PID控制器参数整定PIDcontrollerparameteradjustment（1）理论计算整定法

TheoreticalcalculationandadjustmentmethodPID控制器参数整定PIDcontrollerparameteradjustment（2）工程整定方法Engineeringcalibrationmethods它主要依赖工程经验，直接在控制系统的试验中进行，且方法简单、易于掌握，在工程实际中被广泛采用。Itreliesheavilyonengineeringexperience,directlyinthetestingofcontrolsystems,andthemethodissimpleandeasytomasterandiswidelyusedinengineeringpractice.PID控制器参数的工程整定方法，主要有临界比例法、反应曲线法和衰减法。ThemainengineeringmethodsfortheadjustmentofPIDcontrollerparametersarethecriticalproportionmethod,theresponsecurvemethodandthedecaymethod.三种方法各有其特点，其共同点都是通过试验，然后按照工程经验公式对控制器参数进行整定。Eachofthethreemethodshasitsowncharacteristics,buttheyallhaveincommonthatthecontrollerparametersareadjustedthroughtestsandthenaccordingtoempiricalengineeringformulas.都需要在实际运行中进行最后调整与完善。Allrequirefinaladjustmentandrefinementinactualoperation.现在一般采用的是临界比例法。Thecriticalproportionmethodisnowgenerallyused.工业方面IndustrialA首先预选择一个足够短的采样周期让系统工作；Firstpre-selectashortenoughsamplingperiodtoallowthesystemtooperate.B仅加入比例控制环节，直到系统对输入的阶跃响应出现临界振荡，记下这时的比例放大系数和临界振荡周期；Addonlytheproportionalcontrollinkuntilacriticaloscillationinthestepresponseofthesystemtotheinputoccurs,notingtheproportionalamplificationfactorandthecriticaloscillationperiodatthispoint.

C在一定的控制度下通过公式计算得到PID控制器的参数。TheparametersofthePIDcontrollerareobtainedbyequationatacertaindegreeofcontrol.D系统空载、带载联调，再对PID参数进行微调，直至满足要求。偏差越大，积分越慢；反之则越快。Thesystemisjointlyadjustedwithnoloadandload,andthenthePIDparametersareslightlyadjusteduntiltherequirementsaremet.Thegreaterthedeviation,theslowertheintegration;Onthecontrary,thefaster.整定步骤如下：Therectificationstepsareasfollows.

PID调试一般步骤GeneralstepsforPIDcommissioning（1）确定比例增益PDeterminetheproportionalgainP首先去掉PID的积分项和微分项，一般是令Ti=0、Td=0（具体见PID的参数设定说明），使PID为纯比例调节。输入设定为系统允许的最大值的60%~70%，由0逐渐加大比例增益P，直至系统出现振荡；TheintegralanddifferentialtermsofthePIDarefirstremoved,generallybymakingTi=0andTd=0(seethePIDparametersettinginstructionsfordetails),makingthePIDpurelyproportional.Theinputissetto60%to70%ofthemaximumallowedforthesystemandtheproportionalgainPisgraduallyincreasedfrom0untilthesystemoscillates.再反过来，从此时的比例增益P逐渐减小，直至系统振荡消失，记录此时的比例增益P，设定PID的比例增益P为当前值的60%~70%。比例增益P调试完成。Theninturn,graduallyreducetheproportionalgainPfromthispointuntilthesystemoscillationdisappears,recordtheproportionalgainPatthispoint,andsettheproportionalgainPofthePIDto60%~70%ofthecurrentvalue.ProportionalgainPcommissioningiscompleted.PID调试一般步骤GeneralstepsforPIDcommissioning（2）确定积分时间常数TiDeterminingtheintegrationtimeconstantTi

比例增益P确定后，设定一个较大的积分时间常数Ti的初值。AftertheproportionalgainPhasbeendetermined,setaninitialvalueofTiforalargeintegrationtimeconstant.然后逐渐减小Ti，直至系统出现振荡，之后在反过来，逐渐加大Ti，直至系统振荡消失。ThengraduallyreduceTiuntilthesystemoscillates,afterwhichinturn,graduallyincreaseTiuntilthesystemoscillationdisappears.记录此时的Ti，设定PID的积分时间常数Ti为当前值的150%~180%。积分时间常数Ti调试完成。RecordtheTiatthispointandsettheintegrationtimeconstantTiofthePIDto150%~180%ofthecurrentvalue.TheintegrationtimeconstantTicommissioningiscompleted.010203微分时间常数Td一般不用设定，为0即可。若要设定，与确定P和Ti的方法相同，取不振荡时的30%。ThedifferentialtimeconstantTddoesnotnormallyneedtobeset,butissimply0.Ifitistobeset,itisdeterminedinthesamewayasPandTi,bytaking30%ofthevaluewhennotoscillating.PID调试一般步骤GeneralstepsforPIDcommissioning（3）确定微分时间常数TdDeterminethedifferentialtimeconstantTd各个环节特点Individualsessioncharacteristics（1）比例环节ProportionallinksP参数越小比例作用越强，动态响应越快，消除误差的能力越强。但实际系统是有惯性的，控制输出变化后，实际值y(t)变化还需等待一段时间才会缓慢变化。ThesmallerthePparameterthestrongertheproportionaleffect,thefasterthedynamicresponseandthegreatertheabilitytoeliminateerrors.However,theactualsystemisinertialandtheactualvalueofy(t)changesafterthecontroloutputhaschangedandhastowaitforsometimebeforeitchangesslowly.由于实际系统是有惯性的，比例作用不宜太强，比例作用太强会引起系统振荡不稳定。P参数的大小应在以上定量计算的基础上根据系统响应情况，现场调试决定，通常将P参数由大向小调，以能达到最快响应又无超调(或无大的超调)为最佳参数。Astheactualsystemisinertial,theproportionaleffectshouldnotbetoostrong,theproportionaleffectistoostrongwillcausesystemoscillationinstability.thesizeofthePparametershouldbebasedontheabovequantitativecalculationofthesystemresponse,fieldcommissioningdecision,usuallythePparameterfromlargetosmalladjustment,toachievethefastestresponseandnoovershoot(ornolargeovershoot)forthebestparameters.各个环节特点Individualsessioncharacteristics优点:调整系统的开环比例系数，提高系统的稳态精度，减低系统的惰性，加快响应速度。Advantages:Adjuststheopen-loopscalefactorofthesystem,improvesthesteady-stateaccuracyofthesystem,reducestheinertiaofthesystemandspeedsuptheresponsetime.Disadvantages:WiththePcontrolleronly,anoversizedopen-loopproportionalityfactorwillnotonlyincreasetheovershootofthesystem,butwillalsomakethesystemstabilitymarginsmaller,orevenunstable.缺点:仅用P控制器,过大的开环比例系数不仅会使系统的超调量增大，而且会使系统稳定裕度变小，甚至不稳定。各个环节特点Individualsessioncharacteristics（2）积分环节PointsSession控制器的输出与输入误差信号的积分成正比关系。主要用于消除静差，提高系统的无差度。Theoutputofthecontrollerisproportionaltotheintegrationoftheinputerrorsignal.Itismainlyusedtoeliminatestaticdifferencesandimprovethenon-differentiationofthesystem.积分作用的强弱取决于积分时间常数T,T越大，积分作用越弱，反之则越强。ThestrengthoftheintegralactiondependsontheintegrationtimeconstantT,thelargertheT,theweakertheintegralactionandviceversa.各个环节特点Individualsessioncharacteristics869,7k优点：消除稳态误差

Advantage:Eliminationofsteady-stateerrors.缺点：积分控制器的加入会影响系统的稳定性，使系统的稳定裕度减小。Disadvantage:Theinclusionofanintegralcontrolleraffectsthestabilityofthesystemandreducesthestabilitymarginofthesystem.各个环节特点Individualsessioncharacteristics（3）微分环节Differentiallinks反映偏差信号的变化趋势，并能在偏差信号变得太大之前，在系统中引入一个有效的早期修正信号，从而加快系统的动作速度，减少调节时间。在微分控制中，控制器的输出与输入误差信号的微分（即误差的变化率）成正比关系。Reflectsthetrendofthedeviationsignalandcanintroduceaneffectiveearlycorrectionsignalintothesystembeforethedeviationsignalbecomestoolarge,thusspeedingupthesystem'sactionandreducingregulationtime.Indifferentialcontrol,theoutputofthecontrollerisproportionaltothedifferentialoftheinputerrorsignal(i.e.therateofchangeofthe