电气工程专业英语翻译.docx

电气工程专业英语翻译.docx

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电气工程专业英语翻译

Step7.Tryanoptimaldesign.Ifthetrial-and-errorcompensatorsdonotgiveentirelysatisfactoryperformance,consideradesignbasedonoptimalcontrol.Thesymmetricrootlocuswillshowpossiblerootlocationsfromwhichtoselectlocationsforthecontrolpolesthatmeettheresponsespecifications;youcanselectlocationsfortheestimatorpolesthatrepresentacompromisebetweensensorandprocessnoise.Plotthecorrespondinganditsrobustnesstoparameterchanges.Youcanmodifythepolelocationsuntilabestcompromiseresults.Returningtothesymmetricrootlocuswithdifferentcostmeasuresisoftenapartofthisstep.orcomputationsviathedirectfunctionsIqrandIqecanbeused.Anothervariationonoptimalcontrolislaproposeafindstructurecontrollerwithunknownparameters.formulateaperformancecostfunction.anduseparameteroptimizationtofindagoodsetofparametervalues.

Comparetheoptimaldesignyieldingthemostsatisfactoryfrequencyresponsewiththetransform-methoddesignyouderivedinStep5.SelectthebetterofthetwobeforeproceedingtoStep8.

Step8Buildacomputermodel,andcompute（simulate）theperformanceofthedesign.Afterreachingthebestcompromiseamongprocessmodification,actuatorandsensorselection,andcontrollerdesignchoice,runacomputer,runacomputermodelofthesystem.Thismodelshouldincludeimportantnonlinearitiessuchasactuatorsaturation,realisticnoisesources,andparametervariationsyouexpecttofindduringoperationofthesystem.ThesimulationwilloftenidentifysensitivitiesthatmayleadtogoingbacktoStep5orevenStep2.Designiterationsshouldcontinueuntilthesimulationconfirmsacceptablestabilityandrobustness.Aspartofthissimulationyoucanoftenincludeparameteroptimization,inwhichthecomputertunesthefreeparametersfarbestforbestperformance.Intheearlystagesofdesign,themodelyousimulatewillberelativelysimple;asthedesignprogresses,youwillstudymorecompleteanddetailedmodels.Atthisstepitisalsopossibletocomputeadigitalequivalentoftheanalogcontroller.Somerefinementofthecontrollerparametersmayberequiredtoaccountfortheeffectsofdigitization.Thisallowsthefinaldesigntobeimplementedwithdigitalprocessorlogic.

Iftheresultsofthesimulationprovethedesignsatisfactory,gotoStep9;otherwisereturntoStep1.

Step9.Buildaprototype.Asthefinaltestbeforeproduction,itiscommontobuildandtestaprototype-Atthispointyouverifythequalityofthemodel,discoverunsuspectedvibrationandothermodes,andconsiderwaystoimprovethedesign.Implementthecontrollerusinganembeddedsoftware/hardware.Tunethecontrollerifnecessary.Afterthesetests,youmaywanttoreconsiderthesensor,actuator,andprocessandreturntoStep1-unlesstime,money,orideashaverunout.

Thisoutlineisanapproximationofgoodpractice;otherengineerswillhavevariationsonthesethemes.Insomecasesyoumaywishtocarryouttheminadifferentorder,toomitastep,ortoaddone.Thestagesofsimulationprototypeconstructionvarywidely,dependingonthenatureofthesystem.Forsystemswhereaprototypeisdifficulttotestandrework（forexample,asatellite）orwhereafailureisdangerous（forexample,activestabilizationofahigh-speedcentrifugeorlandingahumanonthemoon）,mostofthedesignverificationisdonethroughsimulationofsomesort.Itmaytaketheformofadigitalnumericalsimulation,alaboratory-scalemodel,orafull-sizelaboratorymodelwithasimulated（forexample,feedbackcontrolforanautomotivefuelthesimulationstepisoftenskippedentirety;designverificationandrefinementareaccomplishedbyworkingwithprototype.

Oneoftheissuesraisedabove（Step6）wastheimportantconsiderationforchangingtheplantitself.Inmanycases,properplantmodificationscanprovideadditionaldampingorincreaseinstiffness,changeinmodeshapes,reductionofsystemresponsetodisturbances,reductionofCoulombfriction,andchangeinthermalcapacityorconductivity,andsoon.Itisworthelaboratingonthisbywayofspecificexamplesfromtheauthors'experiences.Inasemiconductorprocessingexample,theedgeringholdingthewaferwasidentifiedasalimitingfactorinclosed-loopcontrol.Modifyingthethicknessoftheedgeringandusingadifferentcoatingmaterialreducedtheheatlossesand,togetherwithrelocatingoneofthetemperaturesensorsclosertotheedgering.resultedinsignificantimprovementincontrolperformance.Inanotherapplication,thinfilmprocessing,simplychangetheorderofthetwoincomingflowsresultedinsignificantimprovementinuniformityofthefilm.InanapplicationonvapordepositionusingRFplasma,theshapeofthetargetwasmodifiedlobecurvedtocounterthegeometryeffectsof