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1、ISATransactions40(2001)223±234www.elsevier.com/locate/isatransImprovingperformanceusingcascadecontrolandaSmithpredictorIbrahimKayaInonuUniversity,EngineeringFaculty,ElectricalandElectronicsDepartment,44069,Malatya,TurkeyAbstractManyinvestigationshavebeendoneontunin
2、gproportional-integral-derivative(PID)controllersinsingle-inputsingle-output(SISO)systems.However,onlyafewinvestigationshavebeencarriedoutontuningPIDcontrollersincascadecontrolsystems.Inthispaper,anewapproach,namelytheuseofaSmithpredictorintheouterloopofacascadecon
3、trolsystem,isinvestigated.Themethodcanbeusedintemperaturecontrolproblemswherethesecondarypartoftheprocess(theinnerloop)mayhaveanegligibledelaywhiletheprimaryloop(theouterloop)hasatime-delay.Twodif-ferentapproaches,includinganautotuningmethod,to®ndthecontrollerparam
4、etersareproposed.Itisshownbysomeexamplesthattheproposedstructureasexpectedcanprovidebetterperformancethanconventionalcascadecontrol,aSmithpredictorschemeorsinglefeedbackcontrolsystem.#2001ElsevierScienceLtd.Allrightsreserved.Keywords:PIDcontroller;Cascadecontrol;Sm
5、ithpredictor;Processcontrol1.Introductioncontrol,thecorrectiveactionfordisturbancesdoesnotbeginuntilthecontrolledvariabledeviatesManyinvestigationshavebeendoneontuningfromthesetpoint.Asecondarymeasurementpointproportional-integral-derivative(PID)controllersandaseco
6、ndarycontroller,Gc2,incascadetotheinsingle-inputsingle-output(SISO)systems,suchmaincontroller,Gc1,asshowninFig.1,canbeasRefs.[1±3].However,thestandardsinglefeed-usedtoimprovetheresponseofthesystemtoloadbackcontrolloopdoesnotsometimesprovideachanges.goodenoughperfor
7、manceforprocesseswithlongAtypicalexampleisthenaturaldraftfurnacetimedelaysandstrongdisturbances.Cascadecon-temperaturecontrolproblem[10,11],shownintrolloopscanbeusedandareacommonfeatureinFig.2.Whenthereisachangeinhotoiltemperature,theprocesscontrolindustriesforthec
8、ontrolofwhichmayoccurduetoachangeinoil¯owrate,thetemperature,¯owandpressureloops.conventionalsinglefeedbackcontrolsystem,Fig.2,Cascadecontrol(CC)