外文翻译--研究利用差动齿轮系实现机械混合压力.doc

ScienceinChinaSeriesE:TechnologicalSciences2007ScienceinChinaPressSpringer-VerlagStudyofutilizingdifferentialgeartraintoachievehybridmechanismofmechanicalpressHEYuPeng1,ZHAOShengDun2,ZOUJun2&ZHANGZhiYuan21SchoolofMechanicalEngineering,NanjingUniversityofScience&Technology,Nanjing210094,China；2SchoolofMechanicalEngineering,XianJiaotongUniversity,Xian710049,ChinaTheproblemsofhybridinputofmechanicalpressarestudiedinthispaper,withdifferentialgeartrainastransmissionmechanism.Itisproposedthat“adjustable-speedamplitude”or“differential-speedratio”istheimportantparametersforthehybridinputmechanism.Itnotonlydefinestheamplitudeoftheadjustablespeed,butalsodeterminestheratioofthepoweroftheservomotortothepoweroftheconventionalmotor.Thecalculatingequationsoftheratiooftransmissioninallaxes,thepoweroftwomotors,andtheworkingloaddistributionarededuced.Thetwokindsofdrivingschemesareputforwardthattheservomotorandtheconventionalmotorsimultaneouslydriveandtheservomotorandtheconventionalmotorseparatelydrive.Thecalculatingresultsdemonstratethatthelatterschemecanusemuchlowerpoweroftheservomotor,sothisschememakesmanufactureandusecostmuchlower.Thelatterschemeproposesafeasiblewaytoapplythehybridmechanismofmechanicalpressinpracticeengineering.mechanicalpress,hybridmechanism,differentialgeartrain,adjustable-speed1IntroductionAtpresenttherearemanyresearchpapersaboutthehybridmechanismofmechanicalpress,andithasbecomeahotresearchtopic.Thehybridmechanismisamechanismwith2-degree-offreedom(alsocalleddifferentialspeedmechanism),andwhentwoindependentmotionsareinputatthesametime,theoutputthatcansatisfysomemotionrequirementsisobtainedthroughthemotioncompositionofthemechanism.Thehybridmechanismisalsocalledcontrollablemechanism,orhybridmachine.Thepurposeofresearchonhybridmechanismofmechanicalpressisusingconventionalmotorwithbigpowercarryingflywheeltofinishstampingworkpieces；andusesservomotorwithlowpowertoadjustthesliderspeed.Theadvantagesofthehybridmechanismappliedinthemechanicalpressarethatitnotonlycanreducemuchlowermanufacturingcostthanservopress,butalsohasaflexibleworkingvelocityofslider1.Sothemechanicalpressofhybridmechanismarousesmanyresearchersinterestinworkingonit；andthesestudiesaremainlyfocusedonthemulti-barhybridmechanism.DuandGuo1,2havecomprehensivelydiscussedtheseven-barhybridmechanismofmechanicalpress,includingthefeasibleconditionsofcompositionofthelinkagemechanism,theslidermotionanalysis,andthetorqueandpowerdistributionbetweenthetwomotorsaswellastheoptimaldesign.Tonpolynomialinterpolationisalsoinvestigated,andthecomputersimulationshowsthattheresultisindeedattractive.Inaddition,Meng3hasalsoinvestigatedthekinematicalanalysisoftheseven-barmechanism,andtheoptimaldesignhasbeencompletedbasedontheminimumpoweroftheservomotormotor,andMenghasproposedthatthehybridmechanismisaresearchdirectionofthemechanicalpress.Tokuz4firstputforwardofthehybridmechanismandanalyzedthevelocitysynthesisbyusingthedifferentialgeartrain.Hisexperimentconfirmedthefeasibilityofhisconception.Theconceptsoftheadjustable-speedamplitudeanddifferential-speedratioarenotmentionedintheirworks,andtherelationshipbetweenthevelocityvariationandthepowerofthetwomotorswerenotclearlygiven58.Buttheseconceptsareveryimportantandabsolutelynecessaryforthehybridmechanismtoselectthetwomotorspoweranddeterminetheworkingloaddistributionbetweenconventionalmotorandtheservomotor.Inrefs.13theyusedlinkagemechanismtoimplementthehybridinputofmechanicalpress.Themethodisverycomplexbecausethechangeofthelengthandpositionoftheeachbarinlinkagemechanismwillhaveaneffectonthemotionoftheslideofthemechanicalpress.Sosomeprincipalproblemsareusuallyignoredinresearchhybridmechanismcourse,andtheresearchresultsdonnotalwayscoincidewiththepracticeengineeringconditions911.Thegeardifferentialtrainhastwofreedoms,andtheratiosoftransmissionbetweenarbitrarytwoaxesareaconstant.Inordertosimplifythemechanicalmodelandmaketheproblemsmuchprojected,thedifferentialgeartrainisusedastransmissionmechanismtostudythehybridproblemsofthemechanicalpressinthispaper.Thispaperaddressestherelationshipbetweentheadjustable-speedamplitudeandthepowerofthetwomotors,theworkingloaddistributionbetweenthetwomotors,andputsforwardtwodriveschemesoftheconventionalmotorandtheservomotorsimultaneouslyworking,andtwomotorsseparatelyworking.Withthe200-tonmechanicalpressastheengineeringbackground,adrivesystemofthehybridmechanismofthemechanicalpressisdesigned,andthefeasibilityofthetwodriveschemesinmechanicalpressisanalyzed.2TheprincipleofthehybridmechanismTheworkingprincipleofthehybridmechanismofthemechanicalpresswithdifferentialgeartrainisillustratedinFigure1.Thesystemconsistsofconventionalmotor(alsocalledACmachinewithconstantspeed),servomotor,reducingunitI,reducingunitII,differentialgeartrain,andcrankslidemechanism.Theoutputaxisofthedifferentialgeartrainisconnectedwiththecrankshaftofthecrankslidemechanism.Oneofthetwoinputaxeslinkstheconventionalmotorthroughthereducingunit；theotherinputaxislinkstheservomotorthroughthereducingunitII.Thereforethemotionofthecrankshaftiscompletelycontrolledbythemotionsoftheconventionalmotorandtheservomotor.ThereducingunitandthereducingunitIIarerespectivelyinstalledbetweenthetwomotorsandthedifferentialgearunitinthewayofserialinordertobearapartofreducingvelocitytaskofthealltransmissionsystem,becausetoobigdriveratioofthedifferentialgeartrainwillmakeitsdrivingefficiencydecreased.Theangularvelocityoftheconventionalmotorisconstant,soitspriceischeaper.Theangularvelocityoftheservomotorisadjustable,soitspriceisexpensive.Inthesystemofthehybridmechanismtheconstantspeedoftheoutputaxisisprovidedbyhighpowerconventionalmotor；andtheservomotorprovidesitsadjustablespeed.Therefore,inthisway,itnotonlymakestheoutputmotionofthecrankshaftofthemechanicalpressflexible,butalsoavoidsusinghighpowerservomotor.HFigure1Workingprincipleofhybridmechanismofdifferentialgeartrain.3ThevelocitycharacteristicsofthemechanicalpressslideTheworkofthemechanicalpresspresentstheregularityoftheperiodicchange12.ThedisplacementandvelocitychangesofthemechanicalpressslideinanidealworkcirculationareillustratedintheFigure2.Theslidestartstomovefromtopdeadcentertotheworkingstartpointathighvelocity(calledquickfeedingstage).Whentheslideofmechanicalpressapproachestheworkingpoint,itshighvelocityisshiftedtoslowvelocityandthenitbeginstostampworkpieceatlowvelocity(calledlowworkingstage).Thelowvelocityoftheslideistoavoidgreatimpactonthedie,andbenefittheplasticshapingoftheworkpiece.Aftertheslidefinishesthestampingworkandreachesthebottomdeadcenter,theslidecomesbackathighvelocityandstopsatthetopdeadcenter(calledquickbackstage).Hence,themotionvelocityofthemechanicalpressslidecanbedividedthreekinds:highdownvelocityV1,slowworkingvelocityV2,andhighbackvelocityV3.ThevelocityV1andvelocityV3shouldbeaspossibleashighandthevelocityV2shouldbeslowandflexibleinordertoensurehighworkingtimesofthemechanicalpressperminuteandsatisfytherequirementsofdifferenttechnologies.Actuallythemechanicalpressonlyworksinaveryshortcoursebeforethebottomdeadcenter,andintheothercoursesitdoesnotdoworktotheworkpiece.4Thenomenclaturesandequationsofthehybridmechanism4.1TherelationshipoftheangularvelocityinallaxesTherearethreeexternalaxesinthedifferentialgeartrainasillustratedinFigure1.Inordertoconvenientlyexpresstherelationshipofthethreeaxes,theaxisconnectedwiththeconventionalmotoriscalledaxis1,theaxisconnectedwithservomotoriscalledaxis2,andtheaxisconnectedwithcrankshaftiscalledaxis0.Theangularvelocitiesofthethreeaxesarerespectivelyexpressedasn1,n2andn0.ThetorquesofthethreeaxesarerespectivelyexpressedasM1,M2andM0.Becausetherearetwofreedomsinthedifferentialgeartrain,onlythethirdaxisisfixed,suchthatthedriveratiooftheothertwoaxescanbedetermined.SFigure2Idealdisplacementcureoftheslide.4.1.1Theconventionalmotorsinfluenceontheoutputmotion.Whentheservomotorstops,n2=0,onlytheangularvelocityoftheconventionalmotoraffectstheoutputangularvelocitynTheservomotorsinfluenceontheoutputmotion.Whentheconventionalmotorstops,n1=0,onlytheangularvelocityoftheservomotoraffectstheoutputangularvelocityn0,where1n0representsaxis0angularvelocity,and1i20representstotaldriveratiofromaxis2toaxis0includingdifferentialgeartrainandreducingunitIIwhenaxis1(servomotoraxis)isfixed.4.1.3Theconventionalmotorsandservomotorsinfluenceontheoutputmotion.Whentheconventionalmotorandtheservomotorrunatthesametimethroughthecompositionofthedifferentialgeartrain,theoutputvelocitycanbeexpressedas.Becausetheservomotorcanrunatarbitraryangularvelocitybetweenthezeroandspecificvelocityinbothpositiveandnegativedirections,n2canbeexpressedas.whereKistheratiooftheactualangularvelocitytothespecificangularvelocityoftheservomotor；thevalueisarbitrarybetween1and+1,includingzero.n2eisthespecificangularvelocityoftheservomotor.4.2Adjustable-speedamplitudeanddifferential-speedratio4.2.1Adjustable-speedamplitude.Inordertocorrectlydenotethevariablevelocityofthedifferentialgeartrainofthehybridmechanism,theconceptofadjustable-speedamplitudeisintroduced.AsshowninFigure1,adjustable-speedamplitudeistheratio(orpercentage)ofabsolutevalueofupanddownadjustableamounttothebasespeed.Inthedifferentialgeartrainofthehybridmechanism,theadjustable-speedamplitudeequalstheratiovalueofaxis0outputspeedofoperatingasingleservomotoratthespecificspeedtoaxis0outputspeedofoperatingasingleconventionalmotor13.Inthedifferentialgeartrainofthehybridmechanism,theadjustable-speedamplitudeisthemostbasicandthemostimportanttechnologyparameter.Itnotonlydeterminesthematchingrelationshipofthespeedofthetwoinputaxes,4.2.2Differential-speedratio.Thedifferential-speedratioisusuallyusedtoexpressadjustablespeedtechnologyperformanceinthedifferentialgeartrain.Itisanimportanttechnologyparameterofthedifferentialeffectinthedifferentialsystem.Thedifferential-speedratioequalsthereciprocalvalueoftheadjustable-speedamplitude.ItcanbeexpressedasAccordingtothefactthattheangularvelocityisininverseproportiontoitstorqueandthatthesameloadisdrivenbyconventionalmotorandservomotor,anequationexpressedwiththepowersofthetwomotorscanbededuced,whereP1isthepoweroftheconventionalmotor,P1=M1n1.P2isthepoweroftheservomotor,P2=M2n2e.4.3TheworkingloadpowerdistributionSupposingthattheworkingloadpowerofthemechanicalpressisP0,thepowerrelationshipbetweentheconventionalmotor,theservomotorandworkingloadcanbeexpressedasbelow:Figure3Physicalsenseoftheadjustable-speedamplitude.Fromeqs.(9)(11),theoutputpowersoftheconventionalmotorandtheservomotoraredeterminedbythevalueoffactorK,whichisactuallyequaltothechangeratioofangularvelocityoftheservomotor.Hencewhentheoutputangularvelocityrunsindifferentworkingregion,theratioofbearingloadofthetwomotorsisdifferent,too.4.3.1Theoutputaxisrunningatthebasicspeed.Whentheoutputangularvelocityoftheservomotorequalszero,thatis,K=0,P2=0,fromeq.(9),wehave.Heretheconventionalmotorbearsalltheloadingpower.4.3.2Theoutputaxisrunningintheincreasingspeedregion.Theservomotorrunsinthepositivedirection,0K1,andbothP1andP2arepositivevalues,soboththeconventionalmotorandtheservomotorbearapartoftheworkingload.Thustheconventionalmotorbears90.9%100%workingloadandtheservomotorbearsonly09.1%workingload.Thevalueoftheadjustable-speedandthedifferential-speedratiodeter-minetheloaddistributionbetweenthetwomotors.4.3.3Theoutputaxisrunninginthedecreasingspeedregion.Inthedecreasingspeedregion,theservomotorrunsinnegativedirection,andtherangevalueofKis1K0.Byeqs.(9)and(10),theP1ispositive,andtheP2isnegative.Thenegativevalueoftheservomotorpowershowsthattheservomotorpowerisalreadytheworkingresistance.Htheconventionalmotorisnotonlydoingworktotheworkingload,butalsodoingworktotheservomotorpower,Whentheangularspeedisintheregion0n2e,theloadoftheconventionalmotorisThuswhentheoutputangularspeedisinthedecreasingregion,theconventionalmotorconsumesmoreenergythanintheotherregions.Thedecreaseoftheoutputspeedisatthepriceofconsumingtheservomotorinputpower.Inordertosaveenergy,theoutputangularspeedshouldavoidorreducerunninginthedecreasingregion.4.4ThetwodriveschemesofthehybridmechanismofthemechanicalpressAccordingtoeq.(3),theoutputangularvelocityofthehybridmechanismisequaltothereducedvalueoftheirsumoftheangularvelocitiesofboththeconventionalmotorandtheservomotor.AsshowninFigure1,theoutputangularvelocityofthedifferentialgeartrainisconnectedwiththecrankaxisofthemechanicalpress,sothetwoaxeshavethesameangularvelocity.Wheneitheroftheconventionalmotorortheservomotorisdriven,orwhenbothofthemaredriven,thedifferentangularvelocityofthecrankshaftofthemechanicalpresscanbeobtained.Therefore,twokindsoftheschemesofthehybridmechanismofthemechanicalpressareproposed:(i)theconventionalmotorandtheservomotoraresimultaneouslydriven；and(ii)theconventionalmotorandtheservomotorareseparatelydriven.4.4.1Theconventionalmotorandtheservomotorbeingsimultaneouslydriven.Thisschemeshowsthattheangularvelocityofthecrankshaftofthemechanicalpressiscomposedoftheangularvelocityoftheconventionalmotorasthebasicspeedandtheangularvelocityoftheservomotorastheadjustablespeed(Figure3).Theangularvelocityandthepowerscanbecalculatedbyusingeqs.(1)(18).4.4.2Theconventionalmotorandtheservomotorbeingseparatelydriven.Thisschemeshowsthatonlyonemotorisdriveninthehybridinputcourseandatthesametimeanothermotorisbraked,i.e.whenthecrankshaftisindifferentialrunningstage,theconventionalmotorandtheservomotorareseparatelyoperated；thusthedifferentangularvelocityofthecrankshaftcanbeobtained.Theflexiblelowspeedoperation.Whentheconventionalmotorisbrakedandtheservomotorisoperated,n1=0，thebelowequationcanbeobtainedfromeq.(5)Because1K+1,theoutputangularvelocityofthecrankshaftisadjustableandthecrankshafthastworotatingdirections；thereforeitisflexible.Abigvalueofthedriveratio1i20canbedesigned,soaverysmalloutputangularvelocity1n0canbeachieved.Henceinthiscoursetheoutputangularvelocityisflexibleandlow.Whentheservomotorisbrakedandtheconventionalmotorisoperated,n2=0,fromeq.(5),wehave.Crankshafthastworotatingdirections；Figure