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1、CHAPTER1IntroductiontoControlSystemsOBJECTIVESAfterstudyingthischapter,youshouldbeableto:•Distinguishbetweenopen-loopandclosed-loopcontrolsystems.•Understandcontrolsystemblockdiagrams.•Explaintransferfunctions.•Differentiatebetweenanaloganddigitalcontrolsystems.•Knowhowprocesscontrolsystemswork.•
2、Knowhowservomechanismswork.INTRODUCTIONAcontrolsystemisacollectionofcomponentsworkingtogetherunderthedirectionofsomemachineintelligence.Inmostcases,electroniccircuitsprovidetheintelligence,andelectromechanicalcomponentssuchassensorsandmotorsprovidetheinterfacetothephysicalworld.Agoodexampleisthem
3、odernautomobile.Varioussensorssupplytheon-boardcomputerwithinformationabouttheengine’scondition.Thecomputerthencalculatesthepreciseamountoffueltobeinjectedintotheengineandadjuststheignitiontiming.Themechanicalpartsofthesystemincludetheengine,transmission,wheels,andsoon.Todesign,diagnose,orrepairt
4、hesesophisticatedsystems,youmustunderstandtheelectronics,themechanics,andcontrolsystemprinciples.Indayspast,so-calledautomaticmachinesorprocesseswerecontrolledeitherbyanalogelectroniccircuits,orcircuitsusingswitches,relays,andtimers.Sincetheadventoftheinexpensivemicroprocessor,moreandmoredevicesa
5、ndsystemsarebeingredesignedtoincorporateamicroprocessorcontroller.Examplesincludecopyingmachines,soft-drinkmachines,robots,andindustrialprocesscontrollers.Manyofthesemachinesaretakingadvantageoftheincreasedprocessingpowerthatcomeswiththemicroprocessorand,asaconsequence,arebecomingmoresophisticate
6、dandareinclud-ingnewfeatures.Takingagainthemodernautomobileasanexample,theoriginalmoti-vationfortheon-boardcomputerwastoreplacethemechanicalandvacuum-driven12CHAPTER1subsystemsusedinthedistributorandcarburetor.Onceacomputerwasinthedesign,however,makingthesystemmoresophisticatedwasrelativelyeasy—f
7、orexample,self-adjustingfuel/airratioforchangesinaltitude.Also,featuressuchascomputer-assistedenginediagnosticscouldbehadwithoutmuchadditionalcost.Thistrendtowardcom-puterizedcontrolwillnodoubtcontinueinthefuture.1.1CO
