自动化专业英语_lesson1_学生.docx

自动化专业英语_lesson1_学生

第一篇：自动化专业英语_lesson1_学生Lesson1IntroductiontoControlSystemPartΙIntroductionAutomaticcontrolhasplayedavitalroleintheadvancementofengineeringandscience.Inadditiontoitsextremeimportanceinspace-vehicle,missile-guidance,andaircraft-pilotingsystems,etc,automaticcontrolhasbecomeanimportantandintegralpartofmodernmanufacturingandindustrialprocesses.Forexample,automaticcontrolisessentialinsuchindustrialoperationsascontrollingpressure,temperature,humidity,viscosity,andflowintheprocessindustries;tooling,handling,andassemblingmechanicalpartsinthemanufacturingindustries,amongmanyothers.Sinceadvancesinthetheoryandpracticeofautomaticcontrolprovidemeansforattainingoptimalperformanceofdynamicsystems,improvethequalityandlowerthecostofproduction,expandtheproductionrate,relievethedrudgeryofmanyroutine,repetitivemanualoperationsetc,mostengineersandscientistsmustnowhaveagoodunderstandingofthisfield.ThefirstsignificantworkinautomaticcontrolwasJamesWatt’scentrifugalgovernorforthespeedcontrolofasteamengineintheeighteenthcentury.OthersignificantworksintheearlystagesofdevelopmentofcontroltheorywereduetoMinorsky,Hazen,andNyquist,amongmanyothers.In1922Minorskyworkedonautomaticcontrollersforsteeringshipsandshowedhowstabilitycouldbedeterminedbythedifferentialequationsdescribingthesystem.In1934Hazen,whointroducedtheterm“servomechanisms”forpositioncontrolsystems,discusseddesignofrelayservomechanismscapableofcloselyfollowingachanginginput.Duringthedecadeofthe1940’s,frequency-responsemethodsmadeitpossibleforengineerstodesignlinearfeedbackcontrolsystemsthatsatisfiedperformancerequirements.Fromtheendofthe1940’stoearly1950’s,theroot-locusmethodincontrolsystemdesignwasfullydeveloped.Thefrequency-responseandtheroot-locusmethods,whicharethecoreofclassicaltheory,leadtosystemsthatarestableandsatisfyasetofmoreorlessarbitraryperformancerequirements.Suchsystemsare,ingeneral,notoptimalinanymeaningfulsense.Sincethelate1950’s,theemphasisoncontroldesignproblemshasbeenshiftedfromthedesignofoneofmany