自動(dòng)化專業(yè)英語(yǔ)超清晰版

Lesson8SystemDesignandCompensationTechniquesControlsystemsaredesignedtoperformspecifictasks.Therequirementsimposedonthecontrolsystemareusuallyreferredasperformancespecifications.Theygenerallyrelatetoaccuracy,relativestabilityandspeedofresponse.Generally,theperformancespecificationsshouldnotbemorestringentthannecessarytoperformthegiventask.Iftheaccuracyatsteady-stateoperationisofprimeimportanceinagivencontrolsystem,thenweshouldnotrequireunnecessarilyrigidperformancespecificationsonthetransientresponsesincesuchspecificationswillrequireexpensivecomponents.WeshouldrememberthatthemostimportantpartofcontrolsystemdesignistostatethespecificationspreciselysothattheywillyieldanoptimalcontrolsystemforagivenInthislesson,wearegoingtobrieflyintroducethedesignandcompensationprocedureofsingle-input-single-output(SISO),lineartime-invariant(LTI)controlsystemsbythefrequencyresponseandroot-locusapproaches.Compensationisthemodificationofthesystemdynamicstosatisfythegivenspecifications.Settingthegainisthefirststepinadjustingthesystemforsatisfactoryperformance.Inmanycases,increasingthegainvaluewillimprovethesteady-statebehaviorbutwillresultinpoorstabilityoreveninstability.Thenitisnecessarytoredesignthesystem(bymodifyingthestructureorbyincorporatingadditionaldevicesorcomponents)toaltertheoverallbehaviorsothatthesystemwillbehaveasdesired.Fig.8.1showstheconfigurationwheretheGC(s)isplacedinserieswiththeplant.Thisschemeiscalledseriescompensation.Anotherkindofcompensationfeedbackcompensation.Generally,seriescompensationbesimplerthanfeedback

Fig.8.1SeriesIndiscussingcompensators,wefrequentlyuseterminologyasleadnetwork,lagnetwork,andlag-leadnetwork.Ifasinusoidalinputeiisappliedtotheinputofanetworkandthesteady-stateoutputeo(whichisalsosinusoidal)hasaphaselead,thenthenetworkiscalledaleadnetwork.Similarly,ifthesteady-stateoutputeohasaphaselag,thenthenetworkiscalledalagnetwork.Inalag-leadnetwork,phaselagandphaseleadbothoccurintheoutputbutindifferentfrequencyregions;phaselagoccursinthelow-frequencyregionandphaseleadinthehigh-frequencyRoot-locusapproachtocontrolsystemTheroot-locusmethodisagraphicalmethodfordeterminingthelocationsofallclosed-looppolesfromknowledgeofthelocationsoftheopen-looppolesandzerosassomeparameter(usuallythegain)isvariedfromzerotoinfinity.Themethodyieldsaclearindicationoftheeffectsofparameteradjustment.Inpractice,theroot-locusplotofasystemmayindicatethatthedesiredperformancecannotbeachievedjustbytheadjustmentofgain.Thenitisnecessarytoreshapetherootlocitomeettheperformancespecifications.Indesigningacontrolsystem,wemaymodifytheoriginalrootlocibyinsertingasuitablecompensatorGC(s)(asshowninFig.8.1).Oncetheeffectsontherootlocusoftheadditionthepolesand/orzerosarefullyunderstood,wecanreadilydeterminethelocationsoftheandzero(s)ofthecompensatorthatwillreshapetherootlocusasdesired.Inthedesignbytheroot-locusmethod,theroot-lociofthesystemarereshapedthroughtheuseofacompensatorsothatapairofdominantclosed-looppolescanbeplacedatthedesiredlocations.(Usually,damratioandundampednaturalfrequencymaybespecifiedbythelocationsofapairdominantclosed-loopTheadditionofapoletotheopen-looptransferfunctionhastheeffectofpullingtherootlocustotheright,tendingtolowerthesystem’srelativestabilityandtoslowdownthesettlingtheresponse.Theadditionofazerohastheeffectofpullingtherootlocustotheleft,tomakethesystemmorestableandtospeedupthesettlingoftheTheroot-locusapproachtodesignisverypowerfulwhenthespecificationsaregivenintermsoftimeties,suchasthedamratioandundampednaturalfrequency,umovershoot,risetimeandsettlingtime.Letusconsideradesignproblem.Theoriginalsystemeitherisunstableforallvaluesofgainorisstablebuthasundesirabletransientresponsecharacteristics.Inthiscase,thereshaoftherootlocusisnecessaryinorderthatthedominantclosed-looppolesbeatdesiredlocationsinthecomplexplane.InsertinganappropriateleadcompensatorincascadewiththeforwardtransferfunctionmaysolvethisFrequency-responseapproachtocontrolsystemItisimportanttonotethatinacontrolsystemdesign,transient-responseperformanceusuallymostimportant.Inthefrequency-responseapproach,wespecifythetransient-responseintermsofthephaseandgainmargin,resonantpeakmagnitude,thegaincrossoverfrequency,resonantfrequencyandbandwidth. Althoughthecorrelationbetweenthetransientresponseandfrequencyresponseisindirect,thefrequencyspecificationcanbemetconvenientlybymeansofBodediagram.Designinthefrequencyissimpleandstraightforward.Aftertheopenloophasdesignedbyfrequencyresponsemethod,theclosedlooppolesandzeroscanbedetermined.Thetransientresponsecharacteristicsmustbecheckedtoseewhetherthedesignedsystemmeetstherequirementsinthe .Ifitdoesnot,thecompensatorhastobemodifiedandysismustberepeateduntilasatisfactoryresultisBasically,therearetwoapproachesinthe design.OneisthepolarapproachandtheotheristheBodediagramapproach.ItismoreconvenienttoworkwithBodediagram.ABodediagramofthecompensatorcanbesimplyaddedtotheoriginalBodeandthusplottingthecompleteBodediagramisasimplematter.Also,iftheopenloopgainisvaried,themagnitudecurveisshiftedupordownwithoutchangingtheslopeofthecurve,andthephasecurveremainsthesame.AcommonapproachtotheBodediagramisthatwefirstadjusttheopenloopgainsothattherequirementonthesteadystateaccuracyismet.Thenweplotthemagnitudeandphasecurvesofthe pensatedopenloop.Ifthespecificationonthephasemarginandgainmarginarenotsatisfied,thenasuitablecompensatorthatwillreshapetheopenlooptransferfunctionisInmanypracticalcases,compensationisessentiallyacompromisebetweensteady-stateaccuracyandrelativestability.Inordertohaveahighvalueofthevelocityerrorconstantandyetsatisfactoryrelativestability,wefinditnecessarytoreshapetheopenloopfrequencyresponsecurve.Thegaininthelow-frequencyregionshouldbelargeenoughtosatisfythesteady-stateaccuracyrequirements.Forthemedium-frequencyregion(nearthegaincrossoverfrequencyCfrombothdirections),theslopeofthelog-magnitudecurveintheBodediagramshould20dBperdecade.Thisslopeshouldextendoverasufficientwidefrequencybandtoassureaproperphasemargin.Forthehigh-frequencyregion,thegainshouldbeattenuatedasrapidlyaspossibletominimizetheeffectsofnoise.Thebasiccharacteristicsoflead,lag,andlag-leadcompensationareasfollowing.Leadcompensationessentiallyyieldsanappreciableimprovementintransientresponseandasmallchangeinsteady-stateaccuracy.Itmayaccentuatehigh-frequencynoiseeffects.Ontheotherhand,lagcompensationyieldsanappreciableimprovementinsteady-stateaccuracyattheexpenseofincreasingthetransient-responsetime.Lagcompensationwillsuppresstheeffectsofhigh-frequencynoisesignals.Lag-leadcompensationcombinesthecharacteristicsofbothleadcompensationandlagcompensation.NewWpensation2.impose3.stringent4.root-locus5t-](pl.root-loci)根軌indication transient magnitude straightforward accentuate attenuate approach characteristic[7kAriktE5ristik] prime

主要的，最初的，有的，rigid[5ridVid] transient 暫態(tài)響應(yīng)，過(guò)渡反應(yīng)，瞬時(shí)[瞬態(tài)yield 出產(chǎn)，產(chǎn)生，生長(zhǎng)，生產(chǎn) overshoot[5EuvE5Fu:t]

settling phase gain resonant[5rezEnEnt] 23.perkresonantperkbandwidthWeshouldrememberthatthemostimportantpartofcontrolsystemdesignistostatetheperformancespecificationspreciselysothattheywillyieldanoptimalcontrolsystemforagiven本句的結(jié)構(gòu)比較復(fù)雜。在remember后面that所引導(dǎo)的從句是賓語(yǔ)從句，在該從句中“tostate…”是從句中的表語(yǔ)從句。在翻譯這種英語(yǔ)長(zhǎng)句時(shí)，不能夠拘泥于原句的語(yǔ)法結(jié)忠實(shí)于原文的基礎(chǔ)上，將通順的英語(yǔ)(或漢語(yǔ))所表達(dá)的意思轉(zhuǎn)換成用通順的漢語(yǔ)(或英語(yǔ))表達(dá)。Oncetheeffectsontherootlocusoftheadditionofthepolesand/orzerosarefullyunderstood,wecanreadilydeterminethelocationsofthepole(s)andzero(s)ofthecompensatorthatwillreshapetherootlocusasdesired.Once引導(dǎo)條件狀語(yǔ)從句，而且該條件狀語(yǔ)從句是用語(yǔ)態(tài)。Compensator后面that…thepole(sandzero(s)ofthecompensatorInthedesignbytheroot-locusmethod,theroot-lociofthesystemarereshapedthroughtheuseofacompensatorsothatapairofdominantclosed-looppolescanbeplacedatthedesiredlocations.(Usually,thedamratioandundampednaturalfrequencymaybespecifiedbythelocationsofapairofdominantclosed-looppoles.)本句中有兩個(gè)狀語(yǔ)，Inthedesignby…介詞短語(yǔ)作狀語(yǔ)表示場(chǎng)合；sothatapairTheadditionofapoletotheopen-looptransferfunctionhastheeffectofpullingtherootlocustotheright,tendingtolowerthesystem’srelativestabilityandtoslowdownthesettlingoftheresponse.介詞短Theadditionofapoletotheopen-looptransferfunction是句子的主語(yǔ)，現(xiàn)在詞短tendingtolower…作狀語(yǔ)，表示伴隨Insertinganappropriateleadcompensatorincascadewiththefeed-forwardtransferfunctionmaysolvethisproblem.動(dòng)名詞短語(yǔ)Insertingan…是句子的主語(yǔ)。Inthefrequency-responseapproach,wespecifythetransient-responseintermsofthephaseandgainmargin,resonantpeakmagnitude,thegaincrossoverfrequency,resonantfrequencyandbandwidth.在這個(gè)句子中，thephaseandgainmargin,resonantpeakmagnitude,thegaincrossoverfrequency,resonantfrequencyandbandwidth并列成為介詞短語(yǔ)intermsof后面的賓語(yǔ)。ABodediagramofthecompensatorcanbesimplyaddedtotheoriginalBodeandthusplottingthecompleteBodediagramisasimple句子andthusplotting…是一個(gè)并列句，其中動(dòng)名詞短plottingthecompleteBodediagram作主語(yǔ)。Forthemedium-frequencyregion(nearthegaincrossoverfrequencyCfromdirections),theslopeofthelog-magnitudecurveintheBodediagramshouldbe20dBper在中頻段(靠近幅頻曲線的穿越頻率C的兩邊)，在伯德圖中對(duì)數(shù)幅值曲線的斜率應(yīng)該為20dB/dec。語(yǔ)作為定語(yǔ)，用來(lái)修飾Translating 數(shù)詞的譯從1到12是單個(gè)單詞 十 11 十二12從13到19加后綴- 十三13 十九19從20到90加后綴- 二十20 二十三23twenty-九十90百位數(shù)以上五 500five五百六十 561fivehundred(and)sixty-五千六百六十一5,661fivethousandsixhundred(and)sixty-序數(shù)詞翻譯時(shí)加“第……”，如twelfth12th第十 Theoxygenatomisnearly16timesheavierthanthehydrogen氧原子的重量幾乎是氫原子16倍。(16n代替，常n倍，或“比……(大、多、長(zhǎng))n1倍”)Thediodeproduces5timesmoreradiantpowerthanthat這只二極管的輻射功率比那只4倍(是那只5倍)(同上)Thewireistwiceaslongasthat這根電線的長(zhǎng)度是那根的兩倍。(twicen代替，常n倍，或“比……(大、多、長(zhǎng))n1倍”)Theproductionofair-conditionershasincreasedthreetimesthis今年空2倍(3倍)。(如果句中threen表示，那么常譯成“增加了n1倍或增加到n倍”)Theproductionofair-conditionershasincreasedbythreetimesovertheprevious今年空調(diào)的產(chǎn)量比上一年3Theproductionofair-conditionershasdecreasedbythreetimesovertheprevious今年空調(diào)的產(chǎn)量比上一年3Theproductionofair-conditionershasincreasedtothreetimesthis今年空調(diào)的產(chǎn)量3Theproductionofair-conditionershasincreasedbyafactorofthreetimesthisyear.今年空2倍。(如果句中threen表示，那么常n1倍”reduceby 減少reduceto reducebyafactorof 減少9/10(減少reduce10 簡(jiǎn)單的分?jǐn)?shù)one四分之threea/onea/one4 fouranda 3 九分之二十 twenty-fourover

三又五分之 threeandfour-20/83八十三分之二十 twentyovereightthree(twentyeighty-thirds) seventwentieths67/200二百分之六十七sixty-seventwo小數(shù)(nought)pointonetwo(nought)pointtwo(nought)pointonesixpointseveneight時(shí)間或其他60年代初 intheearly本世紀(jì)90年代 intheninetiesofthecentury20世紀(jì)90年代(1990s,1990’s)nineteennineties2005年10月10October10th,200510thOctober,2005October10,2005/10 14′59.38″十五分五十九點(diǎn)fourteenminutesfifty-ninepointthreeeight 乘 times;multiplied 除 divided 等 isequal 大約等 is yequal( 圓括 round[ 方括 squared 斜 65 十的九次 theninthpoweroften/tentothepowernine/tentoninth10- 十的負(fù)五次 entotheminusxxxsecondxsub2根thesquarerootof≥ismorethanorequal≤islessthanorequal>ismore與……成比variesas/isproportional555xapproachestoTranslatethefollowingintoGenerally,weshouldadoptreasonableperformancespecificationswhilewearedesigningacontrolsystem.Weoftenuseleadnetwork,lagnetwork,orlag-leadnetworktoworkascompensatorsincontrolsystemcompensation.Compensationforaclosed-loopcontrolsystemisessentiallyacompromisebetweensteady-stateaccuracyandrelativestabilityofthesystem.ThesubstancereactsthreetimesasfastastheotherThestudentswhotakepartinphysicalactivitieshaveincreasedtoOneinfivewomenbornin1970hassufferedfromdepressionandanxietyintheirthirties,twicetherateofthosebornin1940,theUniversityofLondonhasfound.Translatethefollowinginto半S平面中的理想位置。超前補(bǔ)償可以明顯改善控制系統(tǒng)的暫態(tài)響應(yīng)，對(duì)穩(wěn)態(tài)精度沒(méi)有影響那位要了比平常多一倍的罰款去年鋼產(chǎn)量減少了20%這家造紙廠的產(chǎn)量比1980年增加兩倍ReadingMaterialAnEyeonReactorandComputerAnuclearpowerplantoperatorstaredatthecomputerscreenandyawned.Astheendofalongshiftapproached,hewasfeelingverytiredashelookedaticonsofpumps,pipes,andturbines.Evenso,itwasstillearlyinthereactorstartupsequence.Whenanindicationthatthereactorhadgonecriticalappearedonthescreen,theoperatortriedtorousehimself.Therewasnoneedforhimoranyoneelsetobealarmed,however.Basedonthewaytheoperatorlookedatthescreen,thecomputerhadalreadysensedthathewastiringandhadbeguntoassisttheoperatorinreactorcontrol.Thecomputerzoomedinonthedisplaystheoperatorneededtomonitorreactivityandhighlightedtheimportantdata.Itwouldevenbecapableofassumingpartialreactorcontrolifnecessary.Ataresearchlaboratory,acognitivescientistputadisketteinhercomputerandstudiedthescreen.Thedata