机械专业毕业外文翻译连杆机构.docx
- 文档编号:23875848
- 上传时间:2023-05-21
- 格式:DOCX
- 页数:16
- 大小:78.97KB
机械专业毕业外文翻译连杆机构.docx
《机械专业毕业外文翻译连杆机构.docx》由会员分享,可在线阅读,更多相关《机械专业毕业外文翻译连杆机构.docx(16页珍藏版)》请在冰豆网上搜索。
机械专业毕业外文翻译连杆机构
Linkmechanism
Linkagesincludegaragedoormechanisms,carwipermechanisms,gearshiftmechanisms. Theyareaveryimportantpartofmechanicalengineeringwhichisgivenverylittleattention...
Alinkisdefinedasarigidbodyhavingtwoormorepairingelementswhichconnectittootherbodiesforthepurposeoftransmittingforceormotion. Ineverymachine,atleastonelinkeitheroccupiesafixedpositionrelativetotheearthorcarriesthemachineasawholealongwithitduringmotion. Thislinkistheframeofthemachineandiscalledthefixedlink.
Anarrangementbasedoncomponentsconnectedbyrotaryorslidinginterfacesonlyiscalledalinkage. Thesetypeofconnections,revoluteandprismatic,arecalledlowerpairs.Higherpairsarebasedonpointlineorcurveinterfaces.
Examplesoflowerpairsincludehingesrotarybearings,slideways,universalcouplings.Examplesofhigherpairsincludecamsandgears.
Kinematicanalysis,aparticulargivenmechanismisinvestigatedbasedonthemechanismgeometryplusfactorswhichidentifythemotionsuchasinputangularvelocity,angularacceleration,etc. Kinematicsynthesisistheprocessofdesigningamechanismtoaccomplishadesiredtask. Here,bothchoosingthetypesaswellasthedimensionsofthenewmechanismcanbepartofkinematicsynthesis.
Planar,SpatialandSphericalMechanisms
Aplanarmechanismisoneinwhichallparticlesdescribeplanecurvesisspaceandalloftheplanesareco-planar.. Themajorityoflinkagesandmechanismsaredesignedasplanersystems.Themainreasonforthisisthatplanarsystemsaremoreconvenienttoengineer. Spatialmechanismaarefarmorecomplicatedtoengineerrequiringcomputersynthesis. Planarmechanismsultilisingonlylowerpairsarecalledplanarlinkages.Planarlinkagesonlyinvolvetheuseofrevoluteandprismaticpairs
Aspatialmechanismhasnorestrictionsontherelativemovementoftheparticles.Planarandsphericalmechanismsaresub-setsofspatialmechanisms..Spatialmechanisms/linkagesarenotconsideredonthispage
Sphericalmechanismshasonepointoneachlinkagewhichisstationaryandthestationarypointofallthelinksisatthesamelocation. Themotionsofalloftheparticlesinthemechanismareconcentricandcanberepesentedbytheirshadowonasphericalsurfacewhichiscenteredonthecommonlocation..Sphericalmechanisms/linkagesarenotconsideredonthispage
Mobility
Animportantfactorisconsideringalinkageisthemobilityexpressedasthenumberofdegreesoffreedom. Themobilityofalinkageisthenumberofinputparameterswhichmustbecontrolledindependentlyinordertobringthedevicetoasetposition. Itispossibletodeterminethisfromthenumberoflinksandthenumberandtypesofjointswhichconnectthelinks...
Afreeplanarlinkgenerallyhas3degreesoffreedom(x,y,θ). Onelinkisalwaysfixedsobeforeanyjointsareattachedthenumberofdegreesoffreedomofalinkageassemblywithnlinks=DOF=3(n-1)
Connectingtwolinksusingajointwhichhasonlyondegreeoffreedomaddstwoconstraints.Connectingtwolinkswithajointwhichhastwodegreesoffreedominclude1restrainttothesystems.Thenumberof1DOFjoints=sayj1andthenumberofjointswithtwodegreesoffreedom=sayj2..TheMobilityofasystemisthereforeexpressedasmobility=m=3(n-1)-2j1-j2
Exampleslinkagesshowingthemobilityareshownbelow..
Asystemwithamobilityof0isastructure.Asystemwithamobilityof1canbefixedinpositionmypositioningonlyonelink.Asystemwithamobilityof2requirestwolinkstobepositionedtofixthelinkageposition..
Thisruleisgeneralinnatureandthereareexceptionsbutitcanprovideaveryusefulinitialguideasthethemobilityofanarrangementoflinks...
Grashof'sLaw
Whendesigningalinkagewheretheinputlinkageiscontinuouslyrotatede.g.drivenbyamotoritisimportantthattheinputlinkcanfreelyrotatethroughcompleterevolutions. Thearrangementwouldnotworkifthelinkagelocksatanypoint. ForthefourbarlinkageGrashof'slawprovidesasimpletestforthiscondition
Grashof'slawisasfollows:
Foraplanarfourbarlinkage,thesumoftheshortestandlongestlinkscannotbegreaterthanthesumoftheremaininglinksifthereistobecontinuousrelativerotationbetweentwomembers.
Referringtothe4inversionsofafourbarlinkageshownbelow..Grashof'slawstatesthatoneofthelinks(generallytheshortestlink)willbeabletorotatecontinuouslyifthefollowingconditionismet...
- 配套讲稿:
如PPT文件的首页显示word图标,表示该PPT已包含配套word讲稿。双击word图标可打开word文档。
- 特殊限制:
部分文档作品中含有的国旗、国徽等图片,仅作为作品整体效果示例展示,禁止商用。设计者仅对作品中独创性部分享有著作权。
- 关 键 词:
- 机械 专业 毕业 外文 翻译 连杆机构