1、Chap.2Kinematicsfundamental,2.1BasicConcept2.2DeterminingDegreeofFreedom2.3Howdoesakinematicchainstransformintoamechanism?2.4KinematicDiagramofMechanism2.5PrincipleofMechanismConstitution,2.1BasicConceptsofMechanisms,Degreeoffreedom(自由度)Link（構(gòu)件）KinematicPairs(Joints)（運(yùn)動(dòng)副）MachineElement（機(jī)械零件）Fixedlin

2、k(frame)（機(jī)架）Crank,couple,rocker（曲柄、連桿、搖桿）KinematicChain（運(yùn)動(dòng)鏈）Mechanism（機(jī)構(gòu)）Machine（機(jī)器）,DegreeofFreedom（自由度）,ThesystemsDOFisequaltothenumberofindependentparameterswhichareneededtouniquelydefineitspositioninspaceatanyinstantoftime.,Link（構(gòu)件）:isarigidbodywhichpossessesatleasetwonodeswhicharepointsforattac

3、hmenttootherlinks.,Joint:isaconnectionbetweentwoormorelinks(attheirnodes),whichallowssomemotion,orpotentialmotion,betweentheconnectedlinks.Joints(alsocalledkinematicpairs)canbeclassifiedinseveralways:Bythetypeofcontactbetweentheelements,line,point,orsurface.Bythenumberofdegreeoffreedomallowedatthejo

4、int.Others,Joint(鉸鏈或運(yùn)動(dòng)副),Lowerpairs（低副）:jointswithsurfacecontact,Higherpairs（高副）:jointswithpointorlinecontact,Examplesofhigherpairs,Forceclosedneedexternalforce,DiagramofKinematicpairs（運(yùn)動(dòng)副簡(jiǎn)圖）,MachineElement（機(jī)械零件）:minimumunitduringmanufacturing,Binarylink,Thislinkhasseveralmachineelements,*KinematicC

5、hain（運(yùn)動(dòng)鏈）:anassemblageoflinksandjoints.Iftheselinksareconnectedinsuchawaythatnomotionispossible,alockedchain(structure)result.Mechanism（機(jī)構(gòu)）:akinematicchaininwhichatleaseonelinkhasbeen“grounded”,orattached,totheframeofreference(whichitselfmaybeinmotion);thelinksinthekinematicchainmoveuponeachotherwit

6、hdefiniterelativemotion.Machine（機(jī)器）:acombinationofresistantbodiesarrangedtocompelthemechanicalforcesofnaturetodoworkaccompaniedbydeterminatemotion.,Characteristicsofamachine:1.Composedofman-madeelements2.Theelementsarearrangedtotransmitmotion3.Cantransmitenergy,andfulfillcertainworkforhumanbeing.Con

7、stitution:Partsofamachine:normallytherearefourparts,namely,MotorsandDrivers,Controller,Workingpart,Transmission.,Crank(曲柄):alinkwhichmakesacompleterevolutionandispivotedtoground.Rocker（搖桿）:alinkwhichhasoscillatory(backandforth)rotationandispivotedtoground.Coupler(connectingrod，連桿):alinkwhichhascompl

8、exmotionandisnotpivotedtoground.Ground（機(jī)架）:anylinkorlinksthatarefixed(nonmoving)withrespecttothereferenceframe.(Notethatreferenceframemayinfactitselfbeinmotion.),Fullyrotatingrevolute;Partiallyrotatingrevolute;,Planarmechanism:alllinksofamechanismmoveinplanesthatremainsparalleltoeachother.Otherwise,

9、itisaSpatialmechanism.,2.2DeterminingDegreeofFreedom,1.DegreeofFreedomofaMechanism2.KinematicDiagramofMechanism,1.DOFofaMechanism,1.1ReviewthedefinitionofDOF1.2Degreeoffreedomofalink1.3DOFformulaofaplanarmechanism1.4PointsofAttentiontoCalculatingDOF,1.DOFofaMechanism,1.1DefinitionDOF:Thenumberofinde

10、pendentcoordinatesrequiredtodefineitsposition.1.2Degreeoffreedomofalink,DiagramofLinksandJointsDiagramofMechanisms,1.DOFofaMechanism,1.3DOFformulaofaplanarmechanismM:degreeoffreedomormobilityL:numberoflinksJ1:numberof1DOFjointsJ2:numberof2DOFjoints,1.DOFofaMechanism,Example:,1.DOFofaMechanism,1.4Poi

11、ntsofAttentiontoCalculatingDOFA:Multiplejoints(compoundhinges)B:PassiveDOFC:RedundantConstraints,A:Multiplejoints(compoundhinges),B:PassiveDOF,Howmanymovablelinks,fulljointsandhalfjointsdoesithave?DOFofcammechanism=?,C:RedundantConstraints,2.3Howdoesakinematicchainstransformintoamechanism?,Conclusio

12、n:Atleastonelinkhasbeengrounded2)DOFequalstothenumberofthedrivers,2.4KinematicDiagramofMechanism,1.DefinitionandPurposeThekinematicdiagramservesapurposesimilartothatoftheelectricalschematicorcircuitdiagraminthatitdisplaysonlytheessentialskeletonofthemechanism.Itembodiesthekeydimensionsthataffectitsm

13、otionandexpressestheirconnectionbetweeneachothers.Therearetwoforms:asketch(proportionalbutnotexactlytoscale),andthescaledkinematicdiagram(usuallyusedforfurtheranalysis:position,displacement,velocity,acceleration,forceandtorquetransmission,etc)2.Howtodraw?,2Procedurefordrawingthekinematicdiagramofame

14、chanism1.Analysetheconstruction,motionofthemechanism;Selectavisualangletoobservethetransmissionroutefromthedrivinglinkstooutputlinks.2.Determinethetypeandnumberofkinematicpairs；3.Chooseadrawingplanetoexpressthemechanism；4.Chooseaproperscale(=actuallength(m)/lengthindiagram(mm)todraw.Becarefulaboutth

15、erelativepositionsbetweenthepairs.Forconvenientreference,thelinksarenumbered,whilethejointsarelettered.Theinputandoutputarealsolabeled.5.Calculateandcheckthedegreeoffreedomofthemechanism.,DOF:37-29-2=1,2.5CompositionPrincipleofMechanism,Weknow:1.Amechanismcanbedividedintotwoparts:thebasicmechanism(o

16、neistheframe+drivers+kinematicpairs(whichconnecttheframeanddrivers),theothersaretheleft(drivensystem).2.DOFofamechanism=numberofthedriversThen:DOFoftheleft=0,Assurgroups,Outerpairs,Innerpairs,GradeAssurgroups,Assurgroups,GradeAssurgroups,TheDOFoftheleftgroupiszero,andnogroupcanbedividedfurtherintotwoormorezero-DOFgroups,then