运动的综合凸轮和齿轮Kinematic Synthesis Cams and Gears外文翻译

外文翻译：KinematicSynthesis，CamsandGearsMechanismsformthebasicgeometricalelementsofmanymechanicaldevicesincludingautomaticpackagingmachinery,typewriters,mechanicaltoys,textilemachinery,andothers.Amechanismtypicallyisdesignedtocreateadesiredmotionofarigidbodyrelativetoareferencemember.Kinematicdesign,orkinematicsyntheses,ofmechanismsoftenisthefirststepinthedesignofacompletemachine.Whenforcesareconsidered,theadditionalproblemsofdynamics,bearingloads,stresses,lubrication,andthelikeareintroduced,andthelargerproblembecomesoneofmachinedesign.Akinematiciandefinedkinematicsas“thestudyofthemotionofmechanismsandmethodsofcreatingthem.”Thefirstpartofthisdefinitiondealswithkinematicanalysis.Givenacertainmechanism,themotioncharacteristicsofitscomponentswillbedeterminedbykinematicanalysis.Thestatementofthetasksofanalysiscontainsallprincipaldimensionsofthemechanism,theinterconnectionsofitslinks,andthespecificationoftheinputmotionormethodofactuation.Theobjectiveistofindthedisplacements,velocities,accelerations,shockorjerk(secondacceleration),andperhapshigheraccelerationsofthevariousmembers,aswellasthepathsdescribedandmotionsperformedbycertainelements.Inshort,inkinematicanalysiswedeterminetheperformanceofagivenmechanism.Thesecondpartofdefinitionmaybeparaphrasedintwoways:1.Thestudyofmethodsofcreatingagivenmotionbymeansofmechanisms.2.Thestudyofmethodsofcreatingmechanismshavingagivenmotion.Ineitherversion,themotionisgivenandthemechanismistobefound.Thisistheessenceofkinematicsynthesis.Thuskinematicsynthesisdealswiththesystematicdesignofmechanismsforagivenperformance.Theareaofsynthesismaybegroupedintotwocategories.1.Typesynthesis.Giventherequiredperformance,whattypeofmechanismwillbesuitable?(Geartrains?Linkages?Cammechanisms?)Also,howmanylinksshouldthemechanismhave?Howmanydegreesoffreedomarerequired?Whatconfigurationiddesirable?Andsoon.Deliberationsinvolvingthenumberoflinksanddegreesoffreedomareoftenreferredtoastheprovinceofasubcategoryoftypesynthesiscallednumbersynthesis.2.Dimensionalsynthesis.Thesecondmajorcategoryofkinematicsynthesisisbestdefinedbywayofitsobjective:Dimensionalsynthesisseekstodeterminethesignificantdimensionsandthestartingpositionofamechanismofpreconceivedtypeforaspecifiedtaskandprescribedperformance.Significantdimensionsmeanlinklengthsordistancesonbinary,ternary,andsoon,links,anglesbetweenaxis,cam-contourdimensionsandcam-followerdiameters,eccentricities,gearrations,andsoforth.Amechanismofpreconceivedtypemaybeaslider-cranklinkage,afour-barlinkage,acamwithflatfollower,oramorecomplexlinkageofacertainconfigurationdefinedtopologicallybutnotdimensionally.Therearethreecustomarytasksforkinematicsynthesis:functiongeneration,pathgenerationandmotiongeneration.Infunctiongenerationmechanismsrotationorslidingmotionsofinputandoutputlinksmustbecorrelated.Foranarbitraryfunction,akinematicsynthesistaskmaybetodesignalinkagetocorrelateinputandoutputsuchthattheinputmovesby,theoutputmovesbyfortherange.Inthecaseofrotaryinputandoutput,theanglesofrotationandarethelinearanalogsofandrespectively.Whentheinputlinkisrotatedtoavalueoftheindependent,themechanismina“blackbox”causestheoutputlinktoturntothecorrespondingvalueofthedependentvariable.Thismayberegardedasasimplecaseofamechanicalanalogcomputer.Avarietyofdifferentmechanismscouldbecontainedwithinthe“blackbox”.However,thefour-barlinkageisnotcapableoferror-freegenerationofanarbitraryfunctionandcanmatchthefunctionatonlyalimitednumberofprecisionpoints.Itiswidelyusedinindustrybecausethefour-barlinkageidsimpletoconstructandmaintain.Inpathgenerationmechanismapointona“floatinglink”istotraceapathdefinedwithrespecttoafixedframeofreference.Ifthepathpointsaretobecorrelatedwitheithertimeorinput-linkpositions,thetaskiscalledpathgenerationwithprescribedtiming.Anexampleofpathgenerationmechanismsidafour-barlinkagedesignedtopitchabaseballortennisball.Inthiscasethetrajectoryofpointpwouldbesuchastopickupaballataprescribedlocationandtodelivertheballalongaprescribedpathwithprescribedtimingforreachingasuitablethrow-velocityanddirection.Therearemanysituationsinthedesignofmechanicaldevisesinwhichitisnecessaryeithertoguidearigidbodythroughaseriesofspecified,finitelyseparatedpositionsortoimposeconstraintsonthevelocityand/oraccelerationofthemovingbodyatareducednumberoffinitelyseparatedpositions.Motion-generationorrigid-bodyguidancemechanismrequiresthatanentirebodybeguidedthroughaprescribedmotionsequence.Thebodytobeguidedusuallyisapartofafloatinglink,ofwhichnotonlyisthepathofapointpprescribed,butalsotherotationofalinepassingthroughthepointandembeddedinthebody,.Forinstance,thelinemightrepresentacarrierlinkinaautomaticmachinerywhereapointlocatedonthecarrierlinkhasaprescribedpathwhilethecarrierhasaprescribedangularorientation.Prescribingthemovementofthebucketforabucketloaderidanotherexampleofmotiongenerationmechanisms,thepathoftipofthebucketiscriticalsincethetipmustperformascoopingtrajectoryfollowedbyaliftingandadumpingtrajectory.Theangularorientationofthebucketareequallyimportanttoensurethatloadisdumpedfromthecorrectposition.Acamisaconvenientdevicefortransformingonemotionintoanother.Thismachineelementhasacurvedorgroovedsurfacewhichmateswithafollowerandimpartsmotiontoit.Themotionofthecam(usuallyrotation)istransformedintofolloweroscillation,translation,orboth.Becauseofthevariouscamgeometriesandthelargenumberofcamandfollowercombinations,thecamisanextremelyversatilemechanicalelement.Althoughacamandfollowermaybedesignedformotion,path,orfunctiongeneration,themajorityofapplicationsutilizethecamandfollowerforfunctiongeneration.Themostcommoncamtypesaccordingtocamshapesare:diskorplatetranslating(two-dimensionalorplanar),andcylindrical(three-dimensionalorspatial)cams.Followerscanbeclassifiedinseveralways:accordingtofollowermotion,suchastranslationoroscillation;accordingtowhetherthetranslational(straight-line)followermotionisradialofoffsetfromthecenterofthecamshaft;andaccordingtotheshapeofthefollowercontactsurface(e.g.,flat-face,roller,point(knife-edge),spherical,planarcurved,orspatial-curvedsurface).Inthecaseofadiskcamwitharadial(in-line)translatingrollerfollowerthesmallestcirclethatcanbedrawntangenttothecamsurfaceandconcentricwiththecamshaftisthebasecircle.Thetracerpointisapointatthecenteroftherollercenterandthenormaltothepitchcurve.Thepressureangleistheanglebetweenthedirectionofthepathoftherollercenterandthenormaltothepitchcurvethroughthecenteroftherollerandisthecomplementofthetransmissionangle.Neglectingfriction,thisnormaliscollinearwiththecontactforcebetweenthecamandfollower.Asinalinkage,thepressureanglevariesduringthecycleandisameasureoftheabilityofthecamtotransfermotiveefforttothefollower.Alargepressureanglewillproduceanappreciablelateralforceexertedonthestemofthefollower,which,inthepresenceoffriction,wouldtendtobindthefollowerintheguide.Numerousapplicationsinautomaticmachineryrequireintermittentmotion.Atypicalexamplewillcallforarise-dwell-returnandperhapsanotherdwellperiodofaspecifiednumberofdegreeseach,togetherwitharequiredfollowerdisplacementmeasuredincentimetersordegrees.Thedesigner’sjobistolayoutthecamaccordingly.Thefirstdecisiontobemadeistochoosethecamfollowertype.Thespecifiedapplicationmaydictatethecombinationofthecamandfollower.Somefactorsthatshouldenterintothedecisionare:geometricconsiderations,dynamicconsiderations,environmentalconsiderationsandeconomicmatters.Onceatypeofcamandfollowerpairhasbeenselected,thefollowermotionmustbechosen.Therefore,thevelocity,acceleration,andinsomecasesfurtherderivativesofthedisplacementofthefollowerareofgreatimportance.Gearsaremachineelementsthattransmitmotionbymeansofsuccessivelyengagingteeth.Gearstransmitmotionfromonerotatingshafttoanother,ortoarackthattranslates.Numerousapplicationsexistinwhichaconstantangularvelocityratio(orconstanttorqueratio)mustbetransmittedbetweenshafts.Basedonthevarietyofgeartypesavailable,thereisnorestrictionthattheinputandtheoutputshaftsneedbeeitherin-lineorparallel.Nonlinearangularvelocityratiosarealsoavailablebyusingnoncirculargears.Inordertomaintainaconstantangularvelocity,theindividualtoothprofilemustobeythefundamentallawofgearing:forapairofgearstotransmitaconstantangularvelocityratio,theshapeoftheircontactingprofilesmustbesuchthatthecommonnormalpassesthroughafixedpointonthelineofthecenters.Anytwomatingtoothprofilesthatsatisfythefundamentallawofgearingarecalledconjugateprofiles.Althoughtherearemanytoothshapespossibleinwhichamatingtoothcouldbedesignedtosatisfythefundamentallaw,onlytwoareingeneraluse:thecycloidalandinvoluteprofiles.Theinvolutehasimportantadvantages:itiseasytomanufactureandthecenterdistancebetweenapairofinvolutegearscanbevariedwithoutchangingthevelocityratio.Thuschosetolerancesbetweenshaftsarenotrequiredwhenutilizingtheinvoluteprofile.Thereareseveralstandardgeartypes.Forapplicationswithparallelshafts,straightspurgear,parallelhelical,orherringbonegearsareusuallyused.Inthecaseofintersectingshafts,straightbevelofspiralbevelgearsareemployed.Fornonintersectingandnonparallelshafts,crossedhelical,worm,face,skewbevelorhypoidgearswouldbeacceptablechoices.Forspurgears,thepitchcirclesofmatinggearsaretangenttoeachother.Theyrollononeanotherwithoutsliding.Theaddendumistheheightbywhichatoothprojectsbeyondthepitchcircle(alsotheradialdistancebetweenthepitchcircleandtheaddendumcircle).Theclearanceistheamountbywhichtheaddendum(toothheightbelowthepitchcircle)inagivengearsexceedstheaddendumofitsmatinggear.Thetooththicknessisthedistanceacrossthetoothalongthearcofthepitchcirclewhilethetoothspaceisthedistancebetweenadjacentteethalongthearcofthepitchcircle.Thebacklashistheamountbywhichthewidthofthetoothspaceexceedsthethicknessoftheengagingtoothatthepitchcircle.中文：运动的综合，凸轮和齿轮机构是形成许多机械装置的基本几何结构单元，这些机械装置包括自动包装机、打印机、机械玩具、纺织机械和其他机械等。典型的机构要设计成使刚性构件相对基准构件产生所希望的运动。机构的运动设计或者运动学综合，第一步常常是先设计整部机器。当考虑受力时，要提出动力学方面的问题，轴承的何载、应力、润滑等类似的问题，而较大的问题是机器结构问题。运动学家把运动学定义为“研究机构的运动和创建机构的方法”。这个定义的第一部分就涉及运动学分析。已知一个机构，其构成的运动特性将由运动学分析来确定。叙述运动分析的任务包含机构的主要尺寸、构件间的相互连结和输入运动的技术特性或驱动方法。目的是要找出位移、速度、加速度、冲击或跳动（二阶加速度），和可能发生的各勾结的高阶加速度以及所描述径迹和由某些构件来实现的运动。定义的第二部分可用以下两方面来解释：研究借助机构来产生给定运动的方法研究建造能产生给定运动机构的方法，在两个方案中，运动是给定的而机构是创建的。这就是运动综合的本质。这样运动综合涉及到为给定性能的机构的系统设计。运动综合方面又可以归结为以下两类：1.类型综合。规定所要求的性能，怎样一种类型的机构才是合适的？（齿轮系，连杆机构？还是凸轮机构？）而机构应具有多少构件？需要多少个自由度？怎样的轮廓结构才是所希望的？等等。关于杆件数目和自由度的考虑通常被认为是类型综合中被称作为数量综合的一个分支领域。2.尺寸综合。运动综合的第二个主要类型是通过目标法来确定的最佳方法。尺寸综合试图确定机构的重要尺寸和起动位置，该机构是为着实现规定的任务和预期的性能而事先设想的。所谓重要的尺寸意思是指关于两杆、三杆等的长度或杆间距离，构件数和轴线间的角度，凸轮轮廓尺寸，凸轮随动件的直径，偏心距，齿轮配额等等。预想机构类型可能是曲柄滑块机构、四杆机构，带盘型从动件的凸轮机构，或者是以拓扑学方法而非因次分析法所确定的具有某种结构形状更为复杂的连杆机构。对于运动综合，惯例上有三个任务：函数生成，轨迹生成和运动生成。在函数生成机构中输入和输出构件的转动和移动必须是相互关联的。对于一个任意函数，一个运动综合的任务可能是设计一个连杆机构使输入和输出建立起关系以便使得在的范围内输入按运动，而输出按运动。在输入和输出件回转运动情况下，转角和分别是和的线性模拟。当输入件回转到一个独立值时，在一个“黑箱”的机构中，使输出构件转到相对应的由函数决定的数值上。这可被认为是机械模拟计算机的最简单的情形。各种不同的机构都可以包含在这个“黑箱”内，然而对于任意函数的无误差生成，四杆机构是无能为力的，仅仅可能在有限精确度内与之相匹配。它广泛用于工业上，因为四杆机构在构建和维修上都是简单的。在轨迹生成机构中，在“浮动杆”上一个点要描画一条相对于一个固定坐标系确定的轨迹。如果该轨迹点是既要与时间相关又要与位置相关，该任务被称之为预定周期的轨迹生成。轨迹生成机构的一个例子就是设计来投掷棒球或网球的四杆机构。在这种情况下，点P的轨迹将是这样：在预定的位置捡起一个球，并在预定的时间周期内沿着预定的径迹把球传送出去，能达到合适的速度和方向。机械装置设计中有着许多情形，在这些情形中既要导引刚体通过一系列规定的、受限制的独立位置，又要在减少受限制而且独立的位置的数目时，对运动体的速度和（或）加速度加以约束，那是必要的。运动生成或刚体导引机构要求：一个完整的物体要被导引通过一预定的运动序列。作为被导引的物体通常是“浮动件”的一部分，那不仅是预定点P的轨迹，也是通过该点并嵌入该物体内的线的转动。例如，该线可能代表自动化机械中一个载体件，那是在载体件上的一个点具有一个预定的轨迹的而该载体件又具有一个预定的角度方位。预定方式装料机的吊斗的运动是运动生成机构的另一个例子。吊斗端的轨迹是有极限的。因为其端口必须实现挖掘的运动轨迹，紧跟着要实现提升和倾泻的轨迹。吊斗的角度方位对保证斗中物料从正确的位置倾泻（倒）同样是重要的。凸轮装置是把一种运动改变成另一种运动的方便装置。这种机器零件具有曲面或槽面，该曲面或槽面与从动件相配合并将