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1、ChapterfourConnectionofpartsofacontrolsystem andthe“setting”ofacontroller§4.1Introduction§4.2Connectionofpartsofacontrolsystem§4.3Objectiveoftuningthecontroller§4.4TuningwaysControllerdesigninvolvestheselectionofthecontrolmodestobeusedandthedeterminationofthevaluesofparametersofeach
2、mode.Forcontinuoussystems,theproportionalmodeisusuallycombinedwiththeintegraland/orderivativemodestoformPI,PDandPIDcontroller.Theparametersforthreemodesaretheproportionalgain(),theintegraltime(),andthederivativetimeconstant().§4.1IntroductionWhentheappropriatecontrolmodehasbeenchose
3、nforthegivencontrollerinacontrolsystem,thetwo-thirdsisonlycompletedinthetaskofthecontrolsystemdesign.Thefinalpartofthetakeistoconnectthepartsoftheconstitutepartsofacontrolsystemtogetherfortoformacompletelycontrolsystemandchosethevalueoftheparameters,theproportionalgain(),theintegral
4、time(),andthederivativetimeconstant(),ofthecontrolmodeschoseninthecontroller.ThesimplestdesignmethodistospecifyaPIDcontrollerandthendeterminethecontrolmodeparametersinthefieldduringstart-up.Thisfieldadjustmentiscalled“settingthecontroller”,andaprocedurecalledtheultimatecyclemethodis
5、usedtodeterminethemodeparameters.§4.2ConnectionofpartsofacontrolsystemAclosed-loopfeedbackcontrolsystemmustbeanegativefeedbackcontrolsystem.Forobtaininganegativefeedbackcontrolsystem,weoughttoelectcorrectlyeveryelementconstructingacontrolsystem.§4.1.1Thesymbolruleofeveryelementconst
6、ructingacontrolsystemWhenconnectingeveryelementandformingacontrolsystem,wemustnotetheactionwayofeveryelementconstructingthecontrolsystem.Theactionwayofeveryelementhasusuallytwobasictypes,suchastheair-to-openorair-to-closeofavalve,thedirect-actionorreverse-actionofacontrollerandaposi
7、tiveornegativeobjectandsoon.Theactionwayofeveryelementisdescribedwithasymbolrule.1.ControllerTherearetwoactionwaysincontrollersusually,thedirectactionwaycontrollerandthereverseactionway.Whenthealgebravalueoftheinputsignal,theerrorsignal,enlargingandthealgebravalueoftheoutputsignal,t
8、hecontrolsignal,enl
