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1、2Model-basedFuzzyControlThetaskoffeedbackcontrolsystemsistokeepcontrolledvariablesascloseaspossibletotheirreferencevalues(set-points),whichdefineoperatingpointsofthecontrolledprocess.Aclassicalapproachwhenselectingafeedbackcon-trolalgorithmistofirstidentifyalinearproces
2、smodelatagivenoperatingpoint,thentodesignalinearcontrollerforthatmodelorchoosesettingsofastandardlinearcontroller,usuallyofaPIDtype,seee.g.,[44,85,3,52].However,alinearprocessmodelisonlyanapproximatedescriptionofreality.Moreover,thedesignedcontrollersshouldberobustaga
3、instpossiblechangesinthecharacteristicsofthecontrolledprocesscausedbydisturbancesorchan-gesofitsinternalfeatures.Robustcontrollersshouldensurestabilityofthecontrolsystemandbasiccontrolqualityforaprescribedrangeofdifferencesbetweentheprocessanditsmodelusedforthedesign.F
4、orexample,whenap-plyingclassicalfrequencybaseddesign,certainminimalvaluesofamplitudeandphasemarginsmustbepreserved,assignedonthebasisoffrequencycha-racteristicsoftheprocessmodelwiththecontroller.Theseprescribedminimalvaluesresultfrommanyyearsofpracticalexperience,toac
5、hieveareasonablecompromisebetweenrobustnessandcontrolquality.Asimilarphilosophyisappliedwhendesigningcontrollersbyothermethods,suchastheroot-locusmethod,poleplacement,orpopularintheprocessindustriesselectionofPIDsettingsusingZiegler-Nicholsrulesortablesofsettingsbased
6、onsimplepro-cessmodels,seee.g.,[38,44,85,105].Suchdesignusuallyensuresacorrectoperationofthecontrolsysteminacertainneighborhoodofanoperatingpointforwhichthecontrollerwasdesigned.Thesmallerthenonlinearitiesoftheprocess,thelargerthisneighborhood,ingeneral.Practically,ho
7、wever,controlprocessesareusuallynonlinear,sometimesstronglynonlinear.Iftheyoperateinasmallneighborhoodoftheoperatingpointandcontrolqualityrequirementsarenottoohigh,thenthepresentedde-signphilosophyisusuallysufficient.Ithadtobethecaseduringmanyyearswhencontrollerswereofm
8、echanicalconstruction(e.g.,pneumatic)aswellaslater,whenanalogelectroniccontrollersdominated.Bringingintocontrolpracticecompu
