英文翻譯畢業(yè)設計

汽車轉向系統(tǒng)伴隨汽車電子技術的迅猛發(fā)展，人們對汽車轉向操縱性能的規(guī)定也日益提高。汽車轉向系統(tǒng)已從老式機械轉向、液壓助力轉向（HydraulicPowerSteering,簡稱HPS）、電控液壓助力轉向（ElectricHydraulicPowerSteering,簡稱EHPS）,發(fā)展到電動助力轉向系統(tǒng)（ElectricPowerSteering,簡稱EPS）,最終還將過渡到線控轉向系統(tǒng)（SteerByWire,簡稱SBW）。機械轉向系統(tǒng)是指以駕駛員的體力作為轉向能源,其中所有傳力件都是機械的,汽車的轉向運動是由駕駛員操縱方向盤，通過轉向器和一系列的桿件傳遞到轉向車輪而實現(xiàn)的。機械轉向系由轉向操縱機構、轉向器和轉向傳動機械3大部分構成。一般根據(jù)機械式轉向器形式可以分為：齒輪齒條式、循環(huán)球式、蝸桿滾輪式、蝸桿指銷式。應用最廣的兩種是齒輪齒條式和循環(huán)球式（用于需要較大的轉向力時）。在循環(huán)球式轉向器中，輸入轉向圈與輸出的轉向搖臂擺角是成正比的；在齒輪齒條式轉向器中，輸入轉向圈數(shù)與輸出的齒條位移是成正比的。循環(huán)球式轉向器由于是滾動摩擦形式，因而正傳動效率很高，操作以便且使用壽命長，并且承載能力強，故廣泛應用于載貨汽車上。齒輪齒條式轉向器與循環(huán)球式相比，最大特點是剛性大，構造緊湊重量輕，且成本低。由于這種方式輕易由車輪將反作用力傳至轉向盤，因此具有對路面狀態(tài)反應敏捷的長處，但同步也輕易產生打手和擺振等現(xiàn)象，且其承載效率相對較弱，故重要應用于小汽車及輕型貨車上，目前大部分低端轎車采用的就是齒輪齒條式機械轉向系統(tǒng)。伴隨車輛載重的增長以及人們對車輛操縱性能規(guī)定的提高，簡樸的機械式轉向系統(tǒng)已經(jīng)無法滿足需要，動力轉向系統(tǒng)應運而生，它能在駕駛員轉動方向盤的同步提供助力，動力轉向系統(tǒng)分為液壓轉向系統(tǒng)和電動轉向系統(tǒng)2種。其中液壓轉向系統(tǒng)是目前使用最為廣泛的轉向系統(tǒng)。液壓轉向系統(tǒng)在機械系統(tǒng)的基礎上增長了液壓系統(tǒng)，包括液壓泵、V形帶輪、油管、供油裝置、助力裝置和控制閥。它借助于汽車發(fā)動機的動力驅動液壓泵、空氣壓縮機和發(fā)電機等，以液力、氣力或電力增大駕駛員操縱前輪轉向的力量，使駕駛員可以輕便靈活地操縱汽車轉向，減輕了勞動強度，提高了行駛安全性。液壓助力轉向系統(tǒng)從發(fā)明到目前已經(jīng)有了大概半個世紀的歷史，可以說是一種較為完善的系統(tǒng)，由于其工作可靠、技術成熟至今仍被廣泛應用。它由液壓泵作為動力源，經(jīng)油管道控制閥向動力液壓缸供油，通過活塞桿帶動轉向機構動作，可通過變化缸徑及油壓的大小來變化助力的大小，由此到達轉向助力的作用。老式液壓式動力轉向系統(tǒng)一般按液流的形式可以分為：常流式和常壓式2種類型，也可根據(jù)控制閥形式分為轉閥式和滑閥式。伴隨液壓動力轉向系統(tǒng)在汽車上的日益普及，人們對操作時的輕便性和路感的規(guī)定也日益提高，然而液壓動力轉向系統(tǒng)卻存在許多的缺陷：①由于其自身的構造決定了其無法保證車輛在任何工況下轉動轉向盤時，均有較理想的操縱穩(wěn)定性，即無法同步保證低速時的轉向輕便性和高速時的操縱穩(wěn)定性；②汽車的轉向特性受駕駛員駕駛技術的影響嚴重；③轉向傳動比固定，使汽車轉向響應特性隨車速、側向加速度等變化而變化，駕駛員必須提前針對汽車轉向特性幅值和相位的變化進行一定的操作賠償，從而控制汽車按其意愿行駛。這樣增長了駕駛員的操縱承擔，也使汽車轉向行駛中存在不安全隱患；而此后出現(xiàn)了電控液壓助力系統(tǒng)，它在老式的液壓動力轉向系統(tǒng)的基礎上增長速度傳感器，使汽車可以伴隨車速的變化自動調整操縱力的大小，在一定程度上緩和了老式的液壓轉向系統(tǒng)存在的問題。目前我國生產的商用車和轎車上采用的大多是電控液壓助力轉向系統(tǒng)，它是比較成熟和應用廣泛的轉向系統(tǒng)。盡管電控液壓助力裝置從一定程度上緩和了老式的液壓轉向中輕便性和路感之間的矛盾，然而它還是沒有從主線上處理HPS系統(tǒng)存在的局限性，伴隨汽車微電子技術的發(fā)展，汽車燃油節(jié)能的規(guī)定以及全球性倡導環(huán)境保護，其在布置、安裝、密封性、操縱敏捷度、能量消耗、磨損與噪聲等方面的局限性已越來越明顯，轉向系統(tǒng)向著電動助力轉向系統(tǒng)發(fā)展。電動助力轉向系統(tǒng)是目前汽車轉向系統(tǒng)的發(fā)展方向，其工作原理是：EPS系統(tǒng)的ECU對來自轉向盤轉矩傳感器和車速傳感器的信號進行分析處理后，控制電機產生合適的助力轉矩，協(xié)助駕駛員完畢轉向操作。近幾年來，伴隨電子技術的發(fā)展，大幅度減少EPS的成本已成為也許，日本的大發(fā)汽車企業(yè)、三菱汽車企業(yè)、本田汽車企業(yè)、美國的Delphi汽車系統(tǒng)企業(yè)、TRW企業(yè)及德國的ZF企業(yè)都相繼研制出EPS。Mercedes2Benz和SiemensAutomotive兩大企業(yè)共同投資6500萬英鎊用于開發(fā)EPS，目的是到裝車，年產300萬套，成為全球EPS制造商。到目前為止，EPS系統(tǒng)在輕微型轎車、廂式車上得到廣泛的應用，并且每年以300萬臺的速度發(fā)展。轉向是一種專業(yè)術語，合用于采集部件，聯(lián)絡等，其中容許一艘（艦船）或汽車（轎車）按照預期的方向行駛。一種例外的狀況是鐵路運送由路軌組合在一起鐵路道岔提供轉向功能。許多現(xiàn)代轎車使用齒輪齒條式轉向器，在方向盤末端有轉動齒輪；該齒輪帶動齒條移動，它是一種線性的齒輪緊密配合，從一邊到一邊。這種運動把轉矩通過轉向橫拉桿和一種叫做轉向節(jié)臂的短形臂傳遞給轉向輪的主銷。此前的設計往往采用循環(huán)球式轉向器，而這種轉向器仍然應用在卡車和多用途車輛。這是一種老式的螺母和齒扇設計，該轉向管柱轉動大螺絲（“蝸輪”），它與一種齒扇齒輪嚙合，當蝸輪轉動時，齒扇也隨之轉動，一種安裝在齒扇軸上且與轉向聯(lián)動有關的搖臂帶動轉向節(jié)臂，從而使車輪轉動。循環(huán)球式轉向器通過安裝滾珠減少螺母和螺桿之間的摩擦；兩根導管和螺母內的螺旋管狀通道組合成兩條各自獨立的封閉的鋼球“流到”。齒輪齒條式轉向器設計具有很大程度的反饋和直接轉向“路感”；它也一般不會有任何反彈，或呆滯。缺陷是它是不可調的，因此當它磨損唯一的處理措施更換。循環(huán)球式轉向器的長處是機械優(yōu)勢，因此，它被使用在較大較重的車輛，而齒輪齒條式原本僅限于較小和較輕；由于幾乎普遍采用動力轉向系統(tǒng)，不過，這已不再是一種重要的優(yōu)勢，導致越來越多地在新型汽車應用齒輪齒條式轉向器。循環(huán)球式轉向器設計在中心也有明顯的沖擊，或“死點”。凡一分鐘交替方向盤出不來并不移動轉向機構；這是很輕易可調螺桿的端部來減少磨損，但它并不能完全消除或機制開始磨損很快。這項設計目前仍在使用中，在卡車和其他大型車輛，也應用于迅速轉向，路感與穩(wěn)健性，可維護性，和機械的優(yōu)勢相比不太重要的場所。較小程度的反饋，這樣的設計也有時是一種長處；目前輪碰撞時，使用齒輪齒條轉向的司機只有自己的大拇指受傷，導致方向盤揭開一邊忽然（由于駕駛教練告訴學生把自己的大拇指在前面的方向盤，而非放在左右的內邊緣）。這種效果在像卡車同樣的重型汽車更為明顯；循環(huán)球式轉向防止這種程度的反饋，只是由于它可以在正常狀況下防止可取反饋。轉向連鎖連接轉向器和車輪一般符合一種阿克曼轉向幾何的變化，它交代了一種事實：當轉向是，內輪轉過的半徑比外輪小得多，因此適合駕駛的直路，是不適合波折。由于車輛已成為較重而改用前輪驅動，為了扭轉方向盤，一般的，重要的是體力。為了處理這一問題，汽車業(yè)發(fā)展的動力轉向系統(tǒng)。有兩種類型的助力轉向系統(tǒng)-液壓和電氣/電子。尚有一種液壓-電動混合系統(tǒng)。液壓助力轉向系統(tǒng)（hps）運用油壓供應的一種發(fā)動機驅動泵，以協(xié)助將方向盤轉轉動。電動助力轉向系統(tǒng)（EPS）方式，是較有效率的液壓助力轉向系統(tǒng)，由于電動助力轉向汽車只需要提供協(xié)助時，方向盤被轉動，而液壓泵必須不停運行。在EPS的協(xié)助下是很輕易調整車型，最高車速，甚至駕駛的喜好。此外一種好處是，通過泄漏和處置動力轉向液消除對環(huán)境構成危險。動力轉向的分支是速度可調轉向而轉向是大量輔助以低速行駛，稍微協(xié)助高速。汽車制造商認為，當要停車時駕駛人也許需要做出大量轉向投入，但當時高速行駛時則否則。第一輛有這特點的汽車，是雪鐵龍與其diravi，雖然變化了現(xiàn)代汽車轉向系統(tǒng)資金的投入，但它變化了定心凸輪的壓力，使得方向盤竭力去回到本來的位置。現(xiàn)代速度可調式動力轉向系統(tǒng)，當速度增長時減少了活塞的壓力，予以更直接的感受。這一特點在所有新車正逐漸成為司空見慣。四輪轉向（或全輪轉向）是一種系統(tǒng)，當高速行駛時能增長車輛穩(wěn)定型，而在低速行駛時可以減小轉彎半徑。大多數(shù)的四輪轉向系統(tǒng)，后輪轉向通過單片機和驅動器實現(xiàn)。后輪一般不能反過來，有幾種系統(tǒng)，包括Delphi的quadrasteer，該系統(tǒng)在本田的生產前線，目前輪低速時，容許后輪在相反方向轉向。這使得車輛轉彎半徑較小，有時應用于大型卡車車輛及掛車。ThemotorturningsystemAlongwithautomobileelectronictechnologyswiftandviolentdevelopment,thepeoplealsodaybydayenhancetothemotorturninghandlingqualityrequest.Themotorturningsystemchanged,thehydraulicpressureboostfromthetraditionalmachinerychanges(HydraulicPowerSteering,iscalledHPS),theelectricallycontrolledhydraulicpressureboostchanges(ElectricHydraulicPowerSteering,iscalledEHPS),developstheelectricallyoperatedbooststeeringsystem(ElectricPowerSteering,iscalledEPS),finallyalsowilltransittothelinecontrolsthesteeringsystem(SteerByWire,willbecalledSBW).Themachinerysteeringsystemisrefersbypilot'sphysicalstrengthachievementchangestheenergy,inwhichallpowertransmissionallismechanical,theautomobilechangesthemovementisoperatesthesteeringwheelbythepilot,transmitsthroughthediverterandaseriesofmemberschangesthewheeltorealize.Themechanicalsteeringsystembychangesthecontrolmechanism,thediverterandmajorpartchangesthegearing3tobecomposed.Usuallymaydivideintoaccordingtothemechanicaldiverterform:Thegearracktype,followsroundtheworld-like,thewormbearingadjusterhooptype,thewormbearingadjusterreferssellsthetype.Isthegearracktypeandfollowsusingthebroadesttwokindsroundtheworld-like(usesinneedingtimebigsteeringforce).Infollowsroundtheworld-likeinthediverter,theinputchangesthecircleandtheoutputsteeringarmpivotangleisproportional;Inthegearracktypediverter,theinputchangestheturnandtheoutputrackdisplacementisproportional.Followsroundtheworld-likethediverterbecauseistherollingfrictionform,thusthetransmissionefficiencyisveryhigh,theeaseofoperationalsotheservicelifearelong,moreoverbearingcapacity,thereforewidelyappliesonthetruck.Thegearracktypediverterwithfollowsroundtheworld-likecompares,themostmajorcharacteristicistherigidityisbig,thestructurecompactweightislight,alsothecostislow.Becausethiswaypassesoneasilybythewheelthereactingforcetothesteeringwheel,thereforehastothepavementbehaviorresponsekeenmerit,butsimultaneouslyalsoeasytohavephenomenaandsoongoonandoscillation,alsoitsloadbearingefficiencyrelativeweak,thereforemainlyappliesonthecompactcarandthepickuptruck,atpresentthemajorityoflowendpassengervehicleusesisthegearracktypemachinerysteeringsystem.Alongwiththevehiclescarryingcapacityincreaseaswellasthepeopletothevehicleshandlingqualityrequestenhancement,thesimplemechanicaltypesteeringsystemwerealreadyunabletomeettheneeds,thepowersteeringsystemariseatthehistoricmoment,itcouldrotatethesteeringwheelwhilethepilottoprovidetheboost,thepowersteeringsystemdividesintothehydraulicpressuresteeringsystemandtheelectricallyoperatedsteeringsystem2kinds.Hydraulicpressuresteeringsystemisatpresentusesthemostwidespreadsteeringsystem.Thehydraulicpressuresteeringsystemincreasedthehydraulicsysteminthemechanicalsystemfoundation,includinghydraulicpump,Vshapebandpulley,drilltubing,feedinstallment,boostinstallmentandcontrolvalve.Itwiththeaidofinthemotorcarenginepoweractuationhydraulicpump,theaircompressorandthegeneratorandsoon,bythefluidstrength,thephysicalstrengthortheelectricpowerincreasesthepilottooperatethestrengthwhichthefrontwheelchanges,enablesthepilottobepossiblenimblytooperatemotorturningfacilely,reducedthelaborintensity,enhancedthetravelsecurity.Thehydraulicpressurebooststeeringsystemfrominventedalreadyhadabouthalfcenturyhistorytothepresent,mightsaywasonekindofmoreperfectsystem,becauseitsworkreliable,thetechnologymaturestillwidelyisapplieduntilnow.Ittakesthepowersupplybythehydraulicpump,afteroilpipe-linecontrolvalvestopowerhydrauliccylinderfeed,throughtheconnectingrodimpetusrotationgearmovement,maychangestheboostthroughthechangecylinderboreandtheflowingtubingheadpressuresizethesize,fromthisachievedchangestheboostthefunction.Thetraditionalhydraulicpressuretypepowersteeringsystemmaydivideintogenerallyaccordingtotheliquidflowform:Ordinaryflowtypeandatmosphericpressuretype2kindoftypes,alsomaydivideintoaccordingtothecontrolvalveformtransfersthevalvetypeandtheslide-valvetype.Alongwithhydraulicpressurepowersteeringsystemonautomobiledailypopularization,thepeopletooperateswhentheportabilityandtheroadfeelingrequestalsodaybydayenhance,howeverthehydraulicpressurepowersteeringsystemhasmanyshortcomingsactually:①Becauseitsitselfstructurehaddecideditisunabletoguaranteevehiclesrotatesthesteeringwheelwhenanyoperatingmode,allhastheidealoperationstability,namelyisunablesimultaneouslytoguaranteetimethelowspeedchangestheportabilityandthehighspeedtimeoperationstability;②Theautomobilechangesthecharacteristictodrivethepilottechnicaltheinfluencetobeserious;③Thesteeringratioisfixed,causesthemotorturningresponsecharacteristicalongwithchangesandsoonvehiclespeed,transverseaccelerationtochange,thepilotmustaimatthemotorturningcharacteristicpeak-to-peakvalueandthephasechangeaheadoftimecarriesoncertainoperationcompensation,thuscontrolstheautomobileaccordingtoitswishtravel.Likethisincreasedpilot'soperationburden,alsocausesinthemotorturningtravelnottohavethesecurityhiddendanger;Buthereafterappearedtheelectricallycontrolledhydraulicboostersystem,itincreasesthevelocitygeneratorinthetraditionalhydraulicpressurepowersteeringsystemfoundation,enablestheautomobilealongwiththevehiclespeedchangeautomaticcontrolforcesize,hastoacertainextentrelaxedthetraditionalhydraulicpressuresteeringsystemexistencequestion.Atpresentourcountryproducesonthecommercialvehicleandthepassengervehicleusesmostlyistheelectricallycontrolledhydraulicpressurebooststeeringsystem,itisquitematureandtheapplicationwidespreadsteeringsystem.Althoughtheelectricallycontrolledhydraulicservoalleviatedthetraditionalhydraulicpressurefromcertaindegreetochangebetweentheportabilityandtheroadfeelingcontradiction,howeveritdidnothavefundamentallytosolvetheHPSsystemexistenceinsufficiency,alongwithautomobilemicroelectronictechnologydevelopment,automobilefueloilenergyconservationrequestaswellasglobalinitiativeenvironmentalprotection,itinaspectandsoonarrangement,installment,leak-proofquality,controlsensitivity,energyconsumption,attritionandnoiseinsufficiencyalreadymoreandmoreobvious,thesteeringsystemturnedtowardstheelectricallyoperatedbooststeeringsystemdevelopment.Theelectricallyoperatedbooststeeringsystemisthepresentmotorturningsystemdevelopmentdirection,itsprincipleofworkis:EPSsystemECUaftercomesfromthesteeringwheeltorquesensorandthevehiclespeedsensorsignalcarriesonanalysisprocessing,controlstheelectricalmachinerytohavethesuitableboosttorque,assiststhepilottocompletechangestheoperation.Inthelastfewyears,alongwiththeelectronictechnologydevelopment,reducesEPSthecosttobecomelargescalepossibly,Japansendsthecarcompany,MitsubishiCarcompany,thisfieldcarcompany,US'sDelphiautomobilesystemcompany,TRWCorporationandGermany'sZFCorporationgreatlyalloneafteranotherdevelopsEPS.Mercedes2BenzandSiemensAutomotiveTwobigcompaniesinvested65,000,000poundstouseindevelopingEPS,thegoalaretogetherloadacarto,yearlyproduce300tenthousandsets,becametheglobalEPSmanufacturer.Sofar,theEPSsystemintheslightpassengervehicle,onthetheaterboxtypevehicleobtainsthewidespreadapplication,andeveryyearby300tenthousandspeeddevelopment.Steeringisthetermappliedtothecollectionofcomponents,linkages,etc.whichallowforavessel(ship,boat)orvehicle(car)tofollowthedesiredcourse.Anexceptionisthecaseofrailtransportbywhichrailtrackscombinedtogetherwithrailroadswitchesprovidethesteeringfunction.Themostconventionalsteeringarrangementistoturnthefrontwheelsusingahand–operatedsteeringwheelwhichispositionedinfrontofthedriver,viathesteeringcolumn,whichmaycontainuniversaljointstoallowittodeviatesomewhatfromastraightline.Otherarrangementsaresometimesfoundondifferenttypesofvehicles,forexample,atillerorrear–wheelsteering.Trackedvehiclessuchastanksusuallyemploydifferentialsteering-thatis,thetracksaremadetomoveatdifferentspeedsoreveninoppositedirectionstobringaboutachangeofcourse.Manymoderncarsuserackandpinionsteeringmechanisms,wherethesteeringwheelturnsthepiniongear;thepinionmovestherack,whichisasortoflineargearwhichmesheswiththepinion,fromsidetoside.Thismotionappliessteeringtorquetothekingpinsofthesteeredwheelsviatierodsandashortleverarmcalledthesteeringarm.Olderdesignsoftenusetherecirculatingballmechanism,whichisstillfoundontrucksandutilityvehicles.Thisisavariationontheolderwormandsectordesign;thesteeringcolumnturnsalargescrew(the"wormgear")whichmesheswithasectorofagear,causingittorotateaboutitsaxisasthewormgearisturned;anarmattachedtotheaxisofthesectormovesthepit-manarm,whichisconnectedtothesteeringlinkageandthussteersthewheels.Therecirculatingballversionofthisapparatusreducestheconsiderablefrictionbyplacinglargeballbearingsbetweentheteethofthewormandthoseofthescrew;ateitherendoftheapparatustheballsexitfrombetweenthetwopiecesintoachannelinternaltotheboxwhichconnectsthemwiththeotherendoftheapparatus,thustheyare"recirculated".Therackandpiniondesignhastheadvantagesofalargedegreeoffeedbackanddirectsteering"feel";italsodoesnotnormallyhaveanybacklash,orslack.Adisadvantageisthatitisnotadjustable,sothatwhenitdoeswearanddeveloplash,theonlycureisreplacement.Therecirculatingballmechanismhastheadvantageofamuchgreatermechanicaladvantage,sothatitwasfoundonlarger,heaviervehicleswhiletherackandpinionwasoriginallylimitedtosmallerandlighterones;duetothealmostuniversaladoptionofpowersteering,however,thisisnolongeranimportantadvantage,leadingtotheincreasinguseofrackandpiniononnewercars.Therecirculatingballdesignalsohasaperceptiblelash,or"deadspot"oncenter,whereaminuteturnofthesteeringwheelineitherdirectiondoesnotmovethesteeringapparatus;thisiseasilyadjustableviaascrewontheendofthesteeringboxtoaccountforwear,butitcannotbeentirelyeliminatedorthemechanismbeginstowearveryrapidly.Thisdesignisstillinuseintrucksandotherlargevehicles,whererapidityofsteeringanddirectfeelarelessimportantthanrobustness,maintainability,andmechanicaladvantage.Themuchsmallerdegreeoffeedbackwiththisdesigncanalsosometimesbeanadvantage;driversofvehicleswithrackandpinionsteeringcanhavetheirthumbsbrokenwhenafrontwheelhitsabump,causingthesteeringwheeltokicktoonesidesuddenly(leadingtodrivinginstructorstellingstudentstokeeptheirthumbsonthefrontofthesteeringwheel,ratherthanwrappingaroundtheinsideoftherim).Thiseffectisevenstrongerwithaheavyvehiclelikeatruck;recirculatingballsteeringpreventsthisdegreeoffeedback,justasitpreventsdesirablefeedbackundernormalcircumstances.ThesteeringlinkageconnectingthesteeringboxandthewheelsusuallyconformstoavariationofAckermansteeringgeometry,toaccountforthefactthatinaturn,theinnerwheelisactuallytravelingapathofsmallerradiusthantheouterwheel,sothatthedegreeoftoesuitablefordrivinginastraightpathisnotsuitableforturns.Asvehicleshavebecomeheavierandswitchedtofrontwheeldrive,theefforttoturnthesteeringwheelmanuallyhasincreased-oftentothepointwheremajorphysicalexertionisrequired.Toalleviatethis,automakershavedevelopedpowersteeringsystems.Therearetwotypesofpowersteeringsystems—hydraulicandelectric/electronic.Thereisalsoahydraulic-electrichybridsystempossible.Ahydraulicpowersteering(HPS)useshydraulicpressuresuppliedbyanengine-drivenpumptoassistthemotionofturningthesteeringwheel.Electricpowersteering(EPS)ismoreefficientthanthehydraulicpowersteering,since