毕业设计-外文原文(4万字符)

..Word资料.编号：毕业设计外文翻译（原文）院（系）：电子工程与自动化学院专业：测控技术与仪器学生姓名：XX学号：XXX指导教师单位：电子工程与自动化学院指导教师：XXX职称：XXX2013年5月20日..Word资料.InformationControlAutomaticControlAutomaticcontrolhasplayedavitalroleintheadvanceofengineeringandscience.Inadditiontoitsextremeimportanceinspace-vehiclesystems,missile-guidancesystems,roboticsystems,andthelike,automaticcontrolhasbecomeanimportantandintegralpartofmodernmanufacturingandindustrialprocesses.Forexample,automaticcontrolisessentialinthenumericalcontrolofmachinetoolsinthemanufacturingindustries,inthedesignofautopilotsystemsintheaerospaceindustries,andinthedesignofcarsandtrucksintheautomobileindustries.Itisalsoessentialinsuchindustrialoperationsascontrollingpressure,temperature,humidity,viscosity,andflowintheprocessindustries.Sinceadvancesinthetheoryandpracticeofautomaticcontrolprovidethemeansforattainingoptimalperformanceofdynamicsystems,improvingproductivity,relievingthedrudgeryofmanyroutinerepetitivemanualoperations,andmore,mostengineersandscientistsmustnowhaveagoodunderstandingofthisfield.Controlengineeringisbasedonthefoundationsoffeedbacktheoryandlinearsystemanalysis,anditintegratestheconceptsofnetworktheoryandcommunicationtheory.Thereforecontrolengineeringisnotlimitedtoanyengineeringdisciplinebutisequallyapplicabletoaeronautical,chemical,mechanical,environmental,civil,andelectricalengineering.Forexample,acontrolsystemoftenincludeselectrical,mechanical,andchemicalcomponents.Furthermore,astheunderstandingofthedynamicsofbusiness,social,andpoliticalsystemsincreases,theabilitytocontrolthesesystemswillalsoincrease.Acontrolsystemisaninterconnectionofcomponentsformingasystemconfigurationthatwillprovideadesiredsystemresponse.Thebasisforanalysisofasystemisthefoundationprovidedbylinearsystemtheory,whichassumesacause-effectrelationshipforthecomponentsofasystem.Thereforeacomponentorprocesstobecontrolledcanberepresentedbyablock,asshowninFigure8.1.Theinput-outputrelationshiprepresentsthe..Word资料.cause-and-effectrelationshipoftheprocess,whichinturnrepresentsaprocessingoftheinputsignaltoprovideanoutputsignalvariable,oftenwithapoweramplification.Ingeneral,controlsystemscanbecategorizedasbeingeitheropen-looporclosed–loop.Thedistinguishingfeaturebetweenthesetwotypesofcontrolsystemsistheuseoffeedbackcomparisonforclosed-loopoperation.1．Open-loopControlSystemAnopen-loopcontrolsystemutilizesacontrollerorcontrolactuatortoobtainthedesiredresponse,asshowninFigure8.2.Anopen-loopsystemisasystemwithoutfeedback,simplestformofcontrollingdevices.Figure8.3illustratesasimpletank-levelcontrolsystem.WewishtoholdthetanklevelhwithinreasonableacceptablelimitseventhoughtheoutletflowthroughvalueV1isvaried.ThiscanbeachievedbyirregularmanualadjustmentoftheinletflowratebyvalveV2.Thesystemisnotaprecisionsystem,asitdoesnothavethecapabilityofaccuratelymeasuringtheoutputflowratethroughvalveV1,theinputflowratethroughvalveV2,orthetanklevel.Figure8.4showsthesimplerelationshipthatexistsinthissystembetweentheinput(thedesiredtanklevel)andtheoutput(theactualtanklevel).Thiscontrolsystemdoesnothaveanyfeedbackcomparison,andthetermopenloopisusedtodescribethisabsence.2．Closed-loopControlSystemIncontrasttoanopen-loopcontrolsystem,aclosed-loopcontrolsystemProcessOutputActuatingdeviceProcessDisireouputresponseFigure8.2Anopen-loopsystemhh1vControlsystem(value2vandoperator)Input(desiredtanklevel)Figure8.4Tank-levelcontrolsystemblackdiagram2vOuputFigure8.3Tank-levelcontrolsystemFigure8.1ProcesstobecontrolledOutput(actualtanklevel)Input..Word资料.utilizesanadditionalmeasureoftheactualoutputtocomparetheactualoutputwiththedesiredoutputresponse.Themeasureoftheoutputiscalledthefeedbacksignal.Asimpleclosed-loopfeedbackcontrolsystemisshowninFigure8.5.Afeedbackcontrolsystemisacontrolsystemthattendstomaintainaprescribedrelationshipofonesystemvariabletoanotherbycomparingfunctionsofthesevariablesandusingthedifferenceasameansofcontrol.Closed-loopcontrolsystemsderivetheirvaluableaccuratereproductionoftheinputfromfeedbackcomparison.Anerrordetectorderivesasignalproportionaltothedifferencesbetweentheinputandoutput．Theclosed-loopcontrolsystemdrivestheoutputuntilitequalstheinputandtheerroriszero．Anydifferencesbetweentheactualanddesiredoutputwillbeautomaticallycorrectedinaclosed-loopcontrolsystem．Throughproperdesignthesystemcanbemaderelativelyindependentofsecondaryinputsandchangesincomponentcharacteristics．Figure8.6illustratesanautomatictank-levelcontrolversionofthesystemshowninFigure8.3.ItcanmaintainthedesiredtanklevelhwithinquiteaccuratetoleranceseventhroughtheoutputflowratethroughvalueV1isvaried.Ifthetanklevelisnotcorrect,anerrorvoltageisdeveloped．ThisisamplifiedandappliedtoamotordrivethatadjustsvalueV2inordertorestorethedesiredtanklevelbyadjustingtheinletflowrate．AblockdiagramanalogoustothissystemisshowninFigure8.7.Becausefeedbackcomparisonispresent,thetermclosed-loopisusedtodescribethesystem’soperation.ComparisonControllerProcessDesireoutputresponseMeasurementFigure8.5Close-loopcontrolsystemOutput..Word资料.Duetotheincreasingcomplexityofthesystemundercontrolandtheint