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外文翻译--一个非恒定角速度的弹簧致动的高速凸轮机构的设计 英文版.pdf

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外文翻译--一个非恒定角速度的弹簧致动的高速凸轮机构的设计 英文版.pdf

PergamonMechanicsResearchCommumcations,Vol.27,No.5,pp.529538,2000Copyright©2000ElsevierScienceLtdPrintedintheUSA.Allrightsreserved00936413/00ISseefrontmatterPlhS0093641300001269DESIGNOFASPRINGACTUATEDHIGHSPEEDCAMMECHANISMWITHNONCONSTANTANGULARVELOCITYK.Y.Ahn,J.H.KimandS.H.KimDepartmentofMechanicalEngineering,KAIST,373I,Kusongdong,Yusonggu,Taejon305701,KoreaReceived11January2000acceptedforprint24July2000IntroductionAspringactuatedcammechanismisasimpleandreliabledeviceformovementofheavyloadsatahighaccelerationandforthecontrolofdynamiccharacteristicsoffollowers.SuchamechanismisusedtoavacuumcircuitbreakerVCBwhichcompletesswitchingactionwithinseveraltensmilliseconds\1\.Inthismechanism,theangularvelocityofacamisnotconstantbecausepreloadedspringsrotatethecam.Forthisreason,conventionaldesigntechniquesassumingthatthecamoperatesataconstantvelocityarenotapplicable.Thedesignofaspringactuatedoravariablespeedcamhasseldombeenstudiedintheliterature.RothbartdesignedavariablespeedcamactuatedbyaWhitworthquickreturnmechanismusingagraphicalcamprofilesynthesis\2\.Barkanproposedacamdesignmethodusingtheenergyequationsofasimplifiedspringactuatedcamsystemforonlysimplelonghandcalculation\3\.Thelatterauthorsimplyconsideredenergylossasempiricallosscoefficientsintheenergyequations.Thispaperpresentsthedesignmethodforacamwithnonconstantangularvelocitybasedonthedynamicmodelofacompletespringactuatedcamsystem.Inthederiveddynamicmodel,theexternalforcesandfrictionareincorporated.Thefollowermotion,whichisdependentontherequirementsduringtheclosingperiodofaVCB,isdesignedusingapolynomialfunction.Thecammotionandthecamshapeareobtainedaccordingtotheproposeddesignmethod.Analyzingtheeffectsofthecamshapewithdifferentcaminertia,theinitialcamismodifiedtosatisfythespecificrequirementsofthecamrotationangle.Thesimulationresultsofthedesignedcamarecomparedwiththoseoftheoriginalcam.SpringactuatedcammechanismFigure1showsaVCBwithaspringactuatedhighspeedcammechanism.Theratedvoltageandtheinterruptingcurrentofthebreakerare12kVand40kArespectively.Theessentialpartsofthemechanismconsistofclosing529530K.Y.AHN,J.H.KIMandS.H.KIMspringsthatdrivethecam,afollowerwithopeningsprings,wipespringsthatpushelectriccontacts,andmechanicalpartsincludinglinkagesandlatches.TheclosingprocedureofVCBisasfollowsthecam0inFig.Iisinitiallyconstrainedbytheclosinglatch®inFig.1.Afterreleasingtheclosinglatch,preloadedclosingsprings®inFig.1rotatethecamandthecampushesthefollower®inFig.1toaclosedpositionoftheelectriccontacts®inFig.1.Duringtheclosingoperation,theopeningspringsareextendedandthewipespringscompressedaftertheclosingoftheelectriccontacts.Figure2showsthecamvelocityduringtherapidclosingoperationwithin30msec.Itisobtainedbydifferentiatingthecammotionobtainedaccordingtotheproposeddesignmethod.Itcanbeseenthatthecamvelocitybeginsat0rad/sandreachesover200rad/s.mcamOsupporterelectriccontacts\\fixedandmovablecontactI/,.\\cmsmgclosinglatch\...,camwfixedopeningspr,ng\contact,.vh,4I,Xooenlngot..ivacuum®latchL.rollermovableJIcontact®ff._/follower®wipespringastructurebrepresentationFig.1Vacuumcircuitbreaker°/tI2ool.3oo1oo12o23o354oTime\msec\Fig.2CamvelocityduringrapidclosingoperationPerformancecriteriaofclosingoperationPerformancecriteriamaybeimposedondesigningacam.Inthispaper,thesecriteriaareestablishedbyconsideringtherequirementsduringtheclosingoperationofaVCBandacamfollowersystem.TheHIGHSPEEDCAMMECHANISMDESIGN531performancecriteriaduringtheclosingoperationareasfollows1.Theaverageclosingvelocityofthelast20ofthefullstroke10mmbetweenthefixedandmovablecontactsmustbe1m/s.Thisvelocityisthemostimportantcriterionbecauseitsviolationreducesthelifetimeofelectriccontacts.2.Thecamrotationfroma0toa,mustcompletethefollowerrotationfrom00to0.Thecamrotationangle,aoas,mustbelessthan150°.Subscriptsoandsdenotetheinitialandthefinalpositionrespectively.Thecamradiusoutsidethisrangeisthesameasthecamradiusofas.3.Whenwipespringsarefullycompressedaftertheclosingofelectriccontacts,thevelocityandaccelerationofthefollowershouldbezero.4.TheoveralloperatingtimeofaVCBmustnotexceed35msec.5.Thecamandthefollowershouldbeincontinuouscontactduringtherapidclosingoperationexceptainitialimpact,whichiscausedbytheinitialclearancebetweencamandfollower.Inthesecondcondition,thecamrotationanglecanbecontrolledbycaminertia.Theinitialcaminertiaisassumedastheoriginalcaminertia.Thecaminertiaofthefinaldesignisdeterminedbysatisfyingthespecificrequirementsofthecamrotationangle.Thelastconditionischeckedfromthesimulationofthefinaldesign.Thefollowermotionbasedonthesecriteriaislaterdesigned.DynamicsofspringactuatedcammechanismInthispaper,becausethecamprofileisnotknown,thecamandthefollowerareconsideredasrigidbodiesthatareindependentofeachother.Thecontactforcesbetweencamandfollowerareregardedasexternalforces.Therefore,thecammechanismhastwodegreesoffreedom.TheequationsofmotionofthecamandthefollowerarederivedusingLagrangianequationsrespectively.Consideringthatthecontactforcesareactionandreactionforces,thenonlineardifferentialequationbetweentherotationofcamandfollowerisderived.Forthepurposeofillustration,letusconsiderthesystemmodelshowninFig.3.Here,theconstituentmainlinkssuchascam,followerandmovablecontactsareassumedasrigidbodies.ThecamsupporterisfixedtothegroundframethroughapointO.Theequationsofmotionarederivedasfollows.Generalizedcoordinateqacamangleq20followerangledLoZLagrangesEq.cltoq,777Q....rl,2whereLTVLagrangianQrocnonconservativegeneralizedforceInFig.3,thekineticandpotentialenergiesare1532K.Y.AHN,J.H.KIMandS.H.KIMwhere7Kw,Xw,F,LBe88McghcM/gheM,gLsr88,I,1zmomentofinertiaofcamandfollowerMc,My,M,massofcam,follower,andmovablecontactinthevacuuminterruptLBrdistancebetweenapivotpointoffollowerBandapointFFv,externalforceactingonmovablecontactbythepressuredifferencebetweenatmosphereandvacuum,25kgfhACcsinctct,,,06,/CAChIBCisin8,.,0,,ZCIBEK,Ko,Kwspringstiffnessofclosingspring,openingspring,andwipespringXcs,xos,x,sdisplacementalongaxialdirectionofclosingspring,openingspring,andwipespringOcfolloweranglewhentheelectriccontactsareclosedfixedcamsupportercontactvacuum0InterrupterclosingCcmovableclosingcontactSP9latchCecamicircuitopsnj...._cmasseenterCcam,C/follower¥0Coord.C,,movablecontact,Co,camsupporterFig.3Systemmodelofvacuumcircuitbreaker23NonconservativegeneralizedforcesQ,,careforthecamQi,cT,Tic4forthefollowerQ2,cT2sT2f5whereTcandTzlarethetorquesactingonthecamandthefollowershaftsbycontactforcesbetweencamandfollower,T,andT2sarethefrictiontorquesatthecamshaftandthefollowershaft.Becausewearenotconcernedwiththemeasurementofthefrictiontorquesbutthedirectincorporationoffrictionintothederiveddynamicmodel,TksandT2,areassumedCoulombfrictionshaving4.0and1.0N.mrespectively.TorquesTcandTzibycontactforcesFcandFfbetweencamandfollowerarederivedasfollows.Figure4

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