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1、Chapter3ManipulatoryDevicesSpacerobotsareoftenprovidedwithmanipulatorydevices,whichareessentialtoperformtaskslikegraspingspacecraftorspecimens,operatingtoolsorcamerasforinspectionandmanyotherduties.Inmostcasesthesemanipulatorydevicesareopenkinematiccha
2、ins,whichmaybearsomesimilaritywithhumanarmsoratleastanimallimbs.Thegenerictermarmisusedformanipulatorsthatfollowtheschemeofanopenkinematicchain,eveniftheirstructureisnotanthropomorphic.Thearmsofspacerobotsaresimilar,atleastconceptually,tothoseofindustr
3、ialrobots.Themaintaskofarmsiscarryinganendeffectorofsomesort,abletoperformtherequiredtask,movingittoaprescribedpointinspace,withagivenorientationandoftenfollowingawelldeterminedtrajectory.Thesameanthropomorphicnomenclatureusedinindustrialrobotsappliesa
4、lsotospacerobots:anarmstartsattheshoulder,themiddlejointisanelbowandthejointattheendeffectorisawrist.Ifthelatterisamanipulator,itisdefinedasahand,andusuallyhasfingers.Insomespecializedapplications,thewristcarriesaspecifictooltoperformade-terminedjobinstea
5、dofagenerichand,andtherearecaseswheredifferenteffectorsmaybemountedinanautomaticway.3.1DegreesofFreedomandWorkspaceAnarmisusuallyassumedtobeanopenkinematicchain,madeofrigidbodies(links)connectedtoeachotherbyhinges(joints).Thefirstlinkishingedtothebase,t
6、helastcarriesanendeffectorofsomesort.ThepositionoftheendeffectorisdefinedbyapointP,characterizedbycoordi-natesX=[XYZ]T(3.1)inareferenceframefixedtothebase.Ifthearmmustreachagenericpointinthethree-dimensionalspace,itmusthaveaminimumofthreedegreesoffreedom
7、.Thecorrespondinggeneralizedcoordinates,G.Genta,IntroductiontotheMechanicsofSpaceRobots,SpaceTechnologyLibrary26,73DOI10.1007/978-94-007-1796-1_3,©SpringerScience+BusinessMediaB.V.2012743ManipulatoryDevicesFig.3.1Somepossiblearrangementsofroboticarmsto
8、letthemtoreachapointinthree-dimen-sionalspace.Thethreegeneralizedcoordinatesarealsoshowneitherrotationalortranslationalcoordinates,definingthepositionsofthejoints,canbewritteninavectorθ=[θT1θ2θ3].(3.2)Theyarereferredtoasthejointcoordinat
