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1、ChapterChapter33ModelingModelingTopicstobecoveredinclude:∑Howtoselecttheappropriatemodelcomplexity∑Howtobuildmodelsforagivenplant∑Howtodescribemodelerrors.∑HowtolinearizenonlinearmodelsItalsoprovidesabriefintroductiontocertaincommonlyusedmodels,including∑Statespacemodels∑Highorderdifferentia
2、landhighorderdifferenceequationmodelsTianjinUniversityTheModelsTheModelsThebasicideaoffeedbackistremendouslyThebasicideaoffeedbackistremendouslycompelling.Recallthemouldlevelcontrolcompelling.RecallthemouldlevelcontrolproblemfromChapter2.Actually,thereareonlyproblemfromChapter2.Actually,ther
3、eareonlythreewaysthatacontrollercouldmanipulatethethreewaysthatacontrollercouldmanipulatethevalve:open,closeorleaveitasitis.valve:open,closeorleaveitasitis.Nevertheless,wehaveseenalreadythattheNevertheless,wehaveseenalreadythattheprecisewaythisisdoneinvolvessubtletradeprecisewaythisisdoneinv
4、olvessubtletrade--offsbetweenconflictingobjectives,suchasoffsbetweenconflictingobjectives,suchasspeedofresponseandsensitivitytospeedofresponseandsensitivitytomeasurementnoise.measurementnoise.TianjinUniversityThepowerofamathematicalmodelliesinthefactthatitcanbesimulatedinhypotheticalsituatio
5、ns,besubjecttostatesthatwouldbedangerousinreality,anditcanbeusedasabasisforsynthesizingcontrollers.TianjinUniversityModelComplexityModelComplexityInbuildingamodel,itisimportanttobearinInbuildingamodel,itisimportanttobearinmindthatallrealprocessesarecomplexmindthatallrealprocessesarecomplexan
6、dhenceanyattempttobuildanexactandhenceanyattempttobuildanexactdescriptionoftheplantisusuallyandescriptionoftheplantisusuallyanimpossiblegoal.Fortunately,feedbackisimpossiblegoal.Fortunately,feedbackisusuallyveryforgivingandhence,intheusuallyveryforgivingandhence,inthecontextofcontrolsystemde
7、sign,onecancontextofcontrolsystemdesign,onecanusuallygetawaywithrathersimplemodels,usuallygetawaywithrathersimplemodels,providedtheycapturetheessentialfeaturesprovidedtheycapturetheessentialfeaturesoftheproblem.oftheproblem.TianjinUniversityWeintro