運(yùn)動的綜合凸輪和齒輪Kinematic Synthesis Cams and Gears外文翻譯

外文翻譯：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：運(yùn)動的綜合，凸輪和齒輪機(jī)構(gòu)是形成許多機(jī)械裝置的基本幾何結(jié)構(gòu)單元，這些機(jī)械裝置包括自動包裝機(jī)、打印機(jī)、機(jī)械玩具、紡織機(jī)械和其他機(jī)械等。典型的機(jī)構(gòu)要設(shè)計成使剛性構(gòu)件相對基準(zhǔn)構(gòu)件產(chǎn)生所希望的運(yùn)動。機(jī)構(gòu)的運(yùn)動設(shè)計或者運(yùn)動學(xué)綜合，第一步常常是先設(shè)計整部機(jī)器。當(dāng)考慮受力時，要提出動力學(xué)方面的問題，軸承的何載、應(yīng)力、潤滑等類似的問題，而較大的問題是機(jī)器結(jié)構(gòu)問題。運(yùn)動學(xué)家把運(yùn)動學(xué)定義為“研究機(jī)構(gòu)的運(yùn)動和創(chuàng)建機(jī)構(gòu)的方法”。這個定義的第一部分就涉及運(yùn)動學(xué)分析。已知一個機(jī)構(gòu)，其構(gòu)成的運(yùn)動特性將由運(yùn)動學(xué)分析來確定。敘述運(yùn)動分析的任務(wù)包含機(jī)構(gòu)的主要尺寸、構(gòu)件間的相互連結(jié)和輸入運(yùn)動的技術(shù)特性或驅(qū)動方法。目的是要找出位移、速度、加速度、沖擊或跳動（二階加速度），和可能發(fā)生的各勾結(jié)的高階加速度以及所描述徑跡和由某些構(gòu)件來實(shí)現(xiàn)的運(yùn)動。定義的第二部分可用以下兩方面來解釋：研究借助機(jī)構(gòu)來產(chǎn)生給定運(yùn)動的方法研究建造能產(chǎn)生給定運(yùn)動機(jī)構(gòu)的方法，在兩個方案中，運(yùn)動是給定的而機(jī)構(gòu)是創(chuàng)建的。這就是運(yùn)動綜合的本質(zhì)。這樣運(yùn)動綜合涉及到為給定性能的機(jī)構(gòu)的系統(tǒng)設(shè)計。運(yùn)動綜合方面又可以歸結(jié)為以下兩類：1.類型綜合。規(guī)定所要求的性能，怎樣一種類型的機(jī)構(gòu)才是合適的？（齒輪系，連桿機(jī)構(gòu)？還是凸輪機(jī)構(gòu)？）而機(jī)構(gòu)應(yīng)具有多少構(gòu)件？需要多少個自由度？怎樣的輪廓結(jié)構(gòu)才是所希望的？等等。關(guān)于桿件數(shù)目和自由度的考慮通常被認(rèn)為是類型綜合中被稱作為數(shù)量綜合的一個分支領(lǐng)域。2.尺寸綜合。運(yùn)動綜合的第二個主要類型是通過目標(biāo)法來確定的最佳方法。尺寸綜合試圖確定機(jī)構(gòu)的重要尺寸和起動位置，該機(jī)構(gòu)是為著實(shí)現(xiàn)規(guī)定的任務(wù)和預(yù)期的性能而事先設(shè)想的。所謂重要的尺寸意思是指關(guān)于兩桿、三桿等的長度或桿間距離，構(gòu)件數(shù)和軸線間的角度，凸輪輪廓尺寸，凸輪隨動件的直徑，偏心距，齒輪配額等等。預(yù)想機(jī)構(gòu)類型可能是曲柄滑塊機(jī)構(gòu)、四桿機(jī)構(gòu)，帶盤型從動件的凸輪機(jī)構(gòu)，或者是以拓?fù)鋵W(xué)方法而非因次分析法所確定的具有某種結(jié)構(gòu)形狀更為復(fù)雜的連桿機(jī)構(gòu)。對于運(yùn)動綜合，慣例上有三個任務(wù)：函數(shù)生成，軌跡生成和運(yùn)動生成。在函數(shù)生成機(jī)構(gòu)中輸入和輸出構(gòu)件的轉(zhuǎn)動和移動必須是相互關(guān)聯(lián)的。對于一個任意函數(shù)，一個運(yùn)動綜合的任務(wù)可能是設(shè)計一個連桿機(jī)構(gòu)使輸入和輸出建立起關(guān)系以便使得在的范圍內(nèi)輸入按運(yùn)動，而輸出按運(yùn)動。在輸入和輸出件回轉(zhuǎn)運(yùn)動情況下，轉(zhuǎn)角和分別是和的線性模擬。當(dāng)輸入件回轉(zhuǎn)到一個獨(dú)立值時，在一個“黑箱”的機(jī)構(gòu)中，使輸出構(gòu)件轉(zhuǎn)到相對應(yīng)的由函數(shù)決定的數(shù)值上。這可被認(rèn)為是機(jī)械模擬計算機(jī)的最簡單的情形。各種不同的機(jī)構(gòu)都可以包含在這個“黑箱”內(nèi)，然而對于任意函數(shù)的無誤差生成，四桿機(jī)構(gòu)是無能為力的，僅僅可能在有限精確度內(nèi)與之相匹配。它廣泛用于工業(yè)上，因?yàn)樗臈U機(jī)構(gòu)在構(gòu)建和維修上都是簡單的。在軌跡生成機(jī)構(gòu)中，在“浮動桿”上一個點(diǎn)要描畫一條相對于一個固定坐標(biāo)系確定的軌跡。如果該軌跡點(diǎn)是既要與時間相關(guān)又要與位置相關(guān)，該任務(wù)被稱之為預(yù)定周期的軌跡生成。軌跡生成機(jī)構(gòu)的一個例子就是設(shè)計來投擲棒球或網(wǎng)球的四桿機(jī)構(gòu)。在這種情況下，點(diǎn)P的軌跡將是這樣：在預(yù)定的位置撿起一個球，并在預(yù)定的時間周期內(nèi)沿著預(yù)定的徑跡把球傳送出去，能達(dá)到合適的速度和方向。機(jī)械裝置設(shè)計中有著許多情形，在這些情形中既要導(dǎo)引剛體通過一系列規(guī)定的、受限制的獨(dú)立位置，又要在減少受限制而且獨(dú)立的位置的數(shù)目時，對運(yùn)動體的速度和（或）加速度加以約束，那是必要的。運(yùn)動生成或剛體導(dǎo)引機(jī)構(gòu)要求：一個完整的物體要被導(dǎo)引通過一預(yù)定的運(yùn)動序列。作為被導(dǎo)引的物體通常是“浮動件”的一部分，那不僅是預(yù)定點(diǎn)P的軌跡，也是通過該點(diǎn)并嵌入該物體內(nèi)的線的轉(zhuǎn)動。例如，該線可能代表自動化機(jī)械中一個載體件，那是在載體件上的一個點(diǎn)具有一個預(yù)定的軌跡的而該載體件又具有一個預(yù)定的角度方位。預(yù)定方式裝料機(jī)的吊斗的運(yùn)動是運(yùn)動生成機(jī)構(gòu)的另一個例子。吊斗端的軌跡是有極限的。因?yàn)槠涠丝诒仨殞?shí)現(xiàn)挖掘的運(yùn)動軌跡，緊跟著要實(shí)現(xiàn)提升和傾瀉的軌跡。吊斗的角度方位對保證斗中物料從正確的位置傾瀉（倒）同樣是重要的。凸輪裝置是把一種運(yùn)動改變成另一種運(yùn)動的方便裝置。這種機(jī)器零件具有曲面或槽面，該曲面或槽面與從動件相配合并將