山东大学自动化过程控制期末考试题(英文答案)

1．（1）Theadvantagesanddisadvantagesbetweenfeedbackcontrolandforwardcontrol[反馈控制与前馈控制的优缺点]Feedbackcontrol：①advantagesCorrectiveactionistakenregardlessofthesourceofthedisturbanceReducessensitivityofthecontrolledvariabletodisturbancesandchangesintheprocess②disadvantagea.Nocorrectiveactionoccursuntilafterthedisturbancehasupsettheprocessb.VeryoscillatoryresponsesoreveninstabilityFeedforwardcontrol：①advantagesCorrectivefordisturbancebeforeitupsetstheprocess②disadvantagea.mustbeabletomeasurethedisturbanceb.nocorrectiveactionforunmeasureddisturbance2．（8）Advantagesofon-offcontrolleranditsapplicationsituationAdvantages:simpleandcheapApplication:usedinresidentialheatinganddomesticrefrigerators;limiteduseinprocesscontrolduetocontinuouscyclingofcontrolledvariables.3．（12）Desirablecontrollerfeatures.Stable;adequatedisturbancerejection;quickresponding;goodset-pointtracking;steady-stateerrorsareeliminated.4．（20）whenshouldpredictivecontrolbeused?①ProcessesaredifficulttocontrolwithstandardPIDcontroller,suchaslongtimeconstants②Amongcontrolshavedynamicinteraction③Limitsonprocessandmanipulatedvariablesareimportantfornormalcontrol5．（12）ListGuidanceforCommonControlLoopsuchasflowrate,liquidlevel,gaspressure,temperatureandcomposition.【本题可不看】Forflowrate,PIcontrolisgenerallyusedwithintermediatevaluesofthecontrollergain;Forliquidlevel,integralcontrolactionisoftenused,whilederivativeactionisnotnormallyused;Forgaspressure,PIcontrollerarenormallyusedwithonlyasmallamountofintegralcontrolaction;Fortemperature,PIDcontrollersarecommonlyemployedtoprovidequickerthanthePIcontrollers;Forcomposition,itisgenerallythesameastemperature.6．（16）ListtheadvantagesanddisadvantagesofSmithPredictor.Advantages:a.Improvetheperformanceofsystemcontainingtimedelaysb.Bebeneficialforhandlingdisturbance.Disadvantages:a.Itismodel-based;thatis,adynamicmodelofprocessisrequired1．（2）Anisothermal,irreversiblereactionAkBtakesplaceintheliquidphaseinaconstant-volumereactor.Themixingisnotperfect.Observationsofflowpatternsindicatesthatatwo-tanksystemwithbackmixingasshowninthefigurebelow,shouldapproximatetheimperfectmixing.CA0、CA1、CA2iscomponentofinitialF,V1andV2respect.AssumeFandFRareconstant.Writetheequationdescribingthesystem.Accordingtotheconservationofmass（物料守恒）2212212011)()()()(AARARAARARAAFCCFCFFdtCVdCFFCFCFdtCVdAfterthesimplification,wecanget:))(()()()()(2122121011AARAAARAAACCFFdtCVdCCFCCFdtCVd2．（8）IftheinputYmtoaPIcontrollerchangesstepwise(Ym(s)=2/s)andthecontrolleroutputchangesinitiallyasinthefigurebelow,whatarethevaluesofthecontrollergainandintegraltime?)11()()('))(1)(()(*0*sKsEspdtteteKptpIctIcThus2.1262IccKKThenthecontrollergainKcis3andintegraltimeτI=53．（12）Aprocesshasthetransferfunction12)(2.0sesGs.ComparethePIcontrollersettingsforthefollowingdesignapproach.（1）directsynthesismethod(τc=0.2)（2）directsynthesismethod(τc=1)（3）ITAEperformanceindex(disturbance)（4）ITAEperformanceindex(setpoint)（1）（2）SolveFor1)(sKesGs,Kc·K=c,IThus,=1、θ=0.2、K=2Then,eitherτc=0.2orτc=1,τI=τ=1;Kc=)(2c,whenτc=0.2,Kc=1.25andwhenτc=1,Kc=0.417（3）SolveAccordingto)977.0,859.0()(BAKKAYcB,wecanworkoutthat:Kc=2.069；Accordingto)680.0,674.0()(BAAYIB,wecanworkoutthat:τI=0.497（4）SolveAccordingto)916.0,586.0()(BAKKAYcB,wecanworkoutthat:Kc=；Accordingto)/(BAI,wecanworkoutthat:τI=…。4．（16）Thecascadecontrolsystemisshowninthefigurebelow.(1)Drawtheblockdiagramofthesystem;(2)Explainwhythecascadecontrolsystemcancorrectthedisturbancesinfuelgassupplypressure.（1）Thediagramisbelow（2）Thesecondarycontrolloopliesmorenearthedisturbancesthantheprimaryloop,soitisrespondfasterthantheprimaryloop.Therefore,whenadisturbanceinfuelgassupplypressure,thesecondarycontrolloopcancorrectthedisturbanceassoonaspossibleratherthanthesituationthatthedisturbanceupsetstheprocess.5．（16）Thecascadecontrolsystemisshowninthefigurebelow,whereD1andarevariables.DevelopthetransferfunctionforY1/D2,Y1/Ysp1,Y2/Ysp2andY1/D1.Solve：SupposethatD1=Ysp1=012121222212111122112~22222222111mvppccmpvcdpmmcspcvpdpGGGGGGGGGGGGDYYGEYGEGYEEGGGDGYYGY1212122212121111mppVccmpVcmppvccspGGVGGGGVGGKGGGGGYY222222~11mpVcpvcspGVGGGGGYY112212222221111)1(mppvccmpvcmpvcdGGGGGGGGGGGGGGGDY6．（作业2.1）建立模型。7．（作业8.2）(a)showhowtoobtainthistransferfunctionwithaparallelarrangementoftwomuchsimplerfunctioninthefollowingfigure.1)(1)()('12112211sKKsKKsKsEsP(b)FindexpressionforK1,K2andτIthatcanbeusedtoobtaindesiredvaluesofKc,τDandα(c)VerifytherelationsforKc=3,τD=2,α=0.18．（例12.1）)15)(110(2sseGs，τc=1、3、10(a)Theprocessmodelisperfect(b)Themodelgainisincorrect,9.0~K,insteadofK=2【只需记住】2121212121~,,)1)(1(）（DIccsKKssKesG