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1、IntroductiontoModernControlTheorySeveralfactorsprovidedthestimulusforthedevelopmentofmoderncontroltheory:a.Thenecessaryofdealingwithmorerealisticmodelsofsystem.b.Theshiftinemphasistowardsoptimalcontrolandoptimalsystemdesign.c.Thecontinuingdevelopmentsindigitalcomputertechnology.d.Theshortco
2、mingofpreviousapproaches.e.Recognitionoftheapplicabilityofwell-knownmethodsinotherfieldsofknowledge.Thetransitionfromsimpleapproximatemodels,whichareeasytoworkwith,tomorerealisticmodels,producestwoeffects.First,alargenumberofvariablesmustbeincludedinthemodels.Second,amorerealisticmodelismor
3、elikelytocontainnonlinearitiesandtime-varyingparameters.Previouslyignoredaspectsofthesystem,suchasinteractionswithfeedbackthroughtheenvironment,aremorelikelytobeincluded.Withanadvancingtechnologicalsociety,thereisatrendtowardsmoreambitiousgoals.Thisalsomeansdealingwithcomplexsystemwithalarg
4、enumberofinteractingcomponents.Theneedforgreateraccuracyandefficiencyhaschangertheemphasisoncontrolsystemperformance.Theclassicalspecificationsintermsofpercentovershoot,settingtime,bandwidth,etc.haveinmanycasesgivenwaytooptimalcriteriasuchasminimumenergy,minimumcost,andminimumtimeoperation.
5、Optimizationofthesecriteriamakesitevenmoredifficulttoavoiddealingwithunpleasantnonlinearities.Optimalcontroltheoryoftendictatesthatnonlineartime-varyingcontrollawsareused,evenifthebasicsystemislinearandtime-invariant.Thecontinuingadvancesincomputertechnologyhavehadthreeprincipaleffectsonthe
6、controlsfield.Oneoftheserelatestothegiganticsupercomputers.Thesizeandtheclassoftheproblemsthatcannowbemodeled,analyzed,andcontrolledareconsiderablylargethantheywerewhenthefirsteditionofthisbookwaswritten.Thesecondimpactofthecomputertechnologyhastosowiththeproliferationandwideavailabilityoft
7、hemicrocomputersinhomesandItheworkplace,classicalcontroltheorywasdominatedbygraphicalmethodsbecauseatthetimethatwastheonlywaytosolvecertainproblems,Noweverycontroldesignerhaseasyaccesstopowerfulcomputerpackagesforsystemsanalysisanddesign.Theoldgraphicalm
