大連交通大學(xué)2008屆本科生畢業(yè)設(shè)計(jì)（論文）外文翻譯Developmentofthecompositeflexsplineforacycloid-typeharmonicdriveusingnetshapemanufacturingmethodTheflexsplineforaharmonicdrivemustbeflexibleintheradialdirectionfortheelasticdeformation,butmustbestiffinthetorsionaldirectionforaccuratetransmissionofrotationalmotion.Sincetheserequirementscannotbesatisfiedsimultaneouslywithconventionalmetalssuchassteeloraluminium,inthisworkthecarbonfiberepoxycompositematerialwasemployedfortheflexsplinematerialinordertoincreasethetorsionalstiffnessbytailoringthestackingsequenceandtoimprovethemanufacturingproductivitybymouldingratherthanmachining.Thetoothedcompositeflexsplinewasmanufacturedwiththeelastomericcascadetoolingthatiscomposedofthesteeltoothdie,thesiliconrubbermandrelandthecone-shapedsteelcore.Also,thesteelflexsplinewiththesamedimensionsofthecompositeflexsplinewasmanufacturedbyCNCwirecuttingmethod.Thestaticanddynamicperformancesofthecompositeflexsplineandthesteelflexsplinewereexperimentallytested.Fromthetestresults,itwasfoundthatthedevelopedcompositeflexsplinehadbetterflexibilityintheradialdirectionandhighdampingcapacityatthefundamentalnaturalfrequency.INTRODUCTIONTheharmonicdriveisaspecialgear-drivespeedreductionsystemwhoseoperationprincipleisbasedontheelasticdeformationratherthantherigidbodymotionofgeneralgearingsystem.Ithasmanyadvantages,suchashighspeedreductionratio,highrotationalaccuracy,hightorquetransferperweight,highefficiency,littlebacklashandverycompactsize.Therefore,theharmonicdriveiswidelyacceptedinindustrialrobotsandprecisionmechanisms.Thethreebasiccomponentsoftheharmonicdrivearethecircularspline,flexsplineandellipticalwavegeneratorasshowninFig.1.Thecircularsplinewhichhasusuallytwoorfourmoreteeththantheflexsplineoperatesinrigidbodymotion.Theflexsplineisusuallydesignedasathinwalledcup-typeshape.Theflexsplineiscomposedoftooth,tubeandbosssectionsasshowninFig.2.Figure3showstheprincipleofmotionoftheharmonicdrive.Astheball-bearingmountedontheellipticalwavegeneratordeformstheflexspline大連交通大學(xué)2008屆本科生畢業(yè)設(shè)計(jì)（論文）外文翻譯asshowninFig.3,theteethoftheflexsplineonthemajoraxisoftheellipticalwavegeneratorengagetheteethofthecircularsplineandtheteethoftheflexsplineontheminoraxisdisengagetheteethofthecircularspline.Iftherigidcircularsplineisfixed,theclockwiserotatingofthewavegeneratorproducesthecounterclockwiserotationoftheflexspline.Ifthecircularsplinehas102teethandtheflexsplinehas100teeth,asingleclockwiserevolutionofthewavegeneratormakestheflexsplinerotatecounterclockwisethroughananglecomparabletotwoteeth.Inthiscase,therotationalvelocityratiois50:1.Theflexsplineoftheharmonicdrivethatisthekeyelementforthetorquetransmissionhasthecontradictorydualrolethatmustbeflexibleintheradialdirectionbutmustbestiffinthetorsionaldirectiontoaccuratelytransmitrotationalmotion.Theconventionalflexsplinethatismadeofisotropicmaterialssuchassteeloraluminiumcannotsatisfyperfectlythecontradictorydualrole.Also,themotionoftheharmonicdriveisnotperfectlysmoothbuthasaripplewhichhasthesamefrequencyasthewavegenerator.4Theripplecanproducenoiseandvibrationduringoperation.However,iftheflexsplineismanufacturedusingthecarbonfiberepoxycompositematerial,manydrawbacksoftheharmonicdrivecanbeeliminated,becausethecarbonfiberepoxycompositematerialhashighspecificstiffness,highspecificstrengthandhighmaterialdampingcapacity.Therefore,inthiswork,theflexsplinewasdesignedandmanufacturedwiththehighstrengthcarbonfiberepoxymaterial.Thetorsionalstiffnesswasincreasedwithoutincreasingtheradialstiffnessbytailoringthestackingsequenceandselectionofthefiberorientation.TheinitialstudyonthedevelopmentofthecompositeflexsplinewithcarbonfiberepoxycompositematerialsfortheharmonicdrivewascarriedoutbyOh6andJeong.7Theymanufacturedthecompositeflexsplinebyadhesivelyjoiningtheseparatelymanufacturedpartssuchastheboss,tubeandtoothsections.Sincethepreviousmanufacturingmethodsrequiredseverallaborintensiveoperations,inthiswork,anewnetshapemanufacturingmethodforthecompositeflexsplinewasdevelopedtoincreasemanufacturingproductivity.Inthismethod,allthesectionsoftheflexsplineweremadewithcarbonfiberepoxycompositematerialexceptthebosssection.Sincetheinvolutetoothprofilethatisusedintheconventionalsteelflexsplinehasasmallcurvatureatthededendum,thestressconcentrationattherootoftheteethislargewhentheflexsplineisellipticallydeformed,whichshortensthelifeofthe大連交通大學(xué)2008屆本科生畢業(yè)設(shè)計(jì)（論文）外文翻譯flexspline.。However,thecycloidtoothprofilehaslessstressconcentrationattherootsectionofthetoothbecausethecurvatureislargerthantheinvolutecurve.Thedisadvantageofthecycloidtoothisthedifficultyofmachining.However,iftheteetharemolded,themanufacturingdifficultyofthecycloidandinvoluteteethwillbethesame.Therefore,inthiswork,anepitrochoidtypecycloidcm-ve,8whichwasusuallyemployedforthetoothprofileoftheconventionalcycloiddrive,wasmodifiedandadaptedforthecycloidtypeharmonicdrivetoimprovethestrengthoftheharmonicdrive.Also,thenewcircularsplinethatwasmatedwiththeepitrochoidtypecycloidteethoftheflexsplinewasmanufacturedwiththecarbonfibercompositematerialandsteelpins.Forthemanufacturingmethodofthetoothedflexspline,anelastomericcascadetoolingthatiscomposedofthesteeltoothdie,thesiliconrubberdieandthecone-shapedsteelcorewasused.ThetoothprofileofthesteeldiewasmanufacturedbyaCNCwirecuttingmachine.Also,thesteelflexsplinewiththesamedimensionsofthecompositeflexsplinewasmadebyCNCwirecuttingmachinetocomparetheperformances.Finallythestaticanddynamictestswereperformedtocomparethemechanicalpropertiesofthedevelopedcompositeflexsplines.DESIGNOFTHECYCLOID-TYPEHARMONICDRIVEThecycloiddrivewhoseoperationalprincipleissimilartothatoftheharmonicdriveoperatesintherigidbodymotion.Thecycloiddriveiscomposedoftherigidinternalgearwhichhasmanypins,therigidplanetarygearwhichhastheepitrochoidtoothprofileandtheballbearingmountedontherigidringasshowninFig.4.Therigidringisusuallyassembledintheeccentricinputshaft.Whentheinternalgearisfixed,theeccentricrotationoftherigidringaroundtheinputshaftproducesamotionoftheplanetarygear.Sincethepin-typetoothprofileisusedintheinternalgearandtheepitrochoidtoothprofilewhichismadefromsinusoidalfunctionsisusedintheplanetarygearoftheconventionalcycloiddrive,inthiswork,thepin-typetoothprofilewasusedinthetoothprofileofthecircularsplineandtheepitrochoidtoothprofilewasusedinthetoothprofileoftheflexspline.Thebehaviorofthedesignedtoothprofilewascheckedthroughthecomputersimulationtoavoidthetoothinterferenceduringmotion.Figure5showstheconfigurationofthedevelopedcircularsplineandtheflexsplineofthecycloid-typeharmonicdrive.Table1showsthedimensionsofthedevelopedcycloid-typeharmonicdrive.大連交通大學(xué)2008屆本科生畢業(yè)設(shè)計(jì)（論文）外文翻譯Figure6showstheassembledcrosssectionsoftheconventionalinvolutetypeharmonicdriveandthedevelopedharmonicdrive.Figure7showsacomputergraphicsimulationoftheengagementoftheinvoluteanddevelopedflexsplines.FromFig.7,itwasfoundthattheinterferenceofthetoothofthedevelopedcycloid-typeflexsplinedidnotoccurduringtheflexsplinetranslation.NETSHAPEMANUFACTURINGOFTHEFLEXSPLINEInordertomanufacturethecompositeflexsplinewithnetshapemanufacturingmethod,theelastomericcascadetoolingwhichiscomposedofthetoothdie,thetubedie,thesiliconrubbermandrel,thesteelcoreandthevises,wasusedinthethiswork.Figure8showsthedieassemblyforthemanufacturingofthecompositeflexspline.Inthismethod,theteethofthecompositeflexsplineweremoldedusingthetoothdiewhichhastheshapeoftheinternalgear.TheteethofthetoothdieweremachinedbyaCNCwirecuttingmachine.ThetoothmachiningwascarriedoutintwostagessuchasroughcuttingwithO-3mmdiameterwireandprecisecuttingwith0.1mmdiameterwire.ThetoothdieasshowninFig.9wascomposedoffourpartstomakedemoldingofthecompositeflexsplineeasy.Beforewire-cuttingthetoothprofile,therawdiematerialwasdividedintofourpieces.Aftergrindingthedividedsurfaces,thefourpartswereassembledandthetoothprofilewascutbyaCNCwirecuttingmachine.Figure9(a)showsthetoothdiebeforeassemblyandFig.9