机械手相关的外文文献Word格式文档下载.docx

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Author:

ChristiaanJ.J.Paredis,H.BenjaminBrown,PradeepK.Khosla

Abstract:

Arapidlydeployablemanipulatorsystemcombinestheflexibilityofreconfigurablemodularhardwarewithmodularprogrammingtools,allowingtheusertorapidlycreateamanipulatorwhichiscustom-tailoredforagiventask.Thisarticledescribestwomainaspectsofsuchasystem,namely,theReconfigurableModularManipulatorSystem（RMMS）hardwareandthecorrespondingcontrolsoftware.

1Introduction

Robotmanipulatorscanbeeasilyreprogrammedtoperformdifferenttasks,yettherangeoftasksthatcanbeperformedbyamanipulatorislimitedbymechanicalstructure.Forexample,amanipulatorwell-suitedforprecisemovementacrossthetopofatablewouldprobablynobecapableofliftingheavyobjectsintheverticaldirection.Therefore,toperformagiventask,oneneedstochooseamanipulatorwithanappropriatemechanicalstructure.

Weproposetheconceptofarapidlydeployablemanipulatorsystemtoaddresstheabovementionedshortcomingsoffixedconfigurationmanipulators.AsisillustratedinFigure1,arapidlydeployablemanipulatorsystemconsistsofsoftwareandhardwarethatallowtheusertorapidlybuildandprogramamanipulatorwhichiscustomtailoredforagiventask.

ThecentralbuildingblockofarapidlydeployablesystemisaReconfigurableModularManipulatorSystem（RMMS）.TheRMMSutilizesastockofinterchangeablelinkandjointmodulesofvarioussizesandperformancespecifications.OnesuchmoduleisshowninFigure2.Bycombiningthesegeneralpurposemodules,awiderangeofspecialpurposemanipulatorscanbeassembled.Recently,therehasbeenconsiderableinterestintheideaofmodularmanipulators,forresearchapplicationsaswellasforindustrialapplications.However,mostofthesesystemslackthepropertyofreconfigurability,whichiskeytotheconceptofrapidlydeployablesystems.TheRMMSisparticularlyeasytoreconfigurethankstoitsintegratedquick-couplingconnectorsdescribedinSection3.

EffectiveuseoftheRMMSrequires,TaskBasedDesignsoftware.Thissoftwaretakesasinputdescriptionsofthetaskandoftheavailablemanipulatormodules;

itgeneratesasoutputamodularassemblyconfigurationoptimallysuitedtoperformthegiventask.Severaldifferentapproacheshavebeenusedsuccessfullytosolvesimpli-fiedinstancesofthis

Athirdimportantbuildingblockofarapidlydeployablemanipulatorsystemisaframeworkforthegenerationofcontrolsoftware.Toreducethecomplexityofsoftwaregenerationforreal-timesensor-basedcontrolsystems,asoftwareparadigmcalledsoftwareassemblyhasbeenproposedintheAdvancedManipulatorsLaboratoryatCMU.Thisparadigmcombinestheconceptofreusableandreconfigurablesoftwarecomponents,asissupportedbytheChimerareal-timeoperatingsystem,withagraphicaluserinterfaceandavisualprogramminglanguage,inplementedinOnika.

Althoughthesoftwareassemblyparadigmprovidesthesoftwareinfrastructureforrapidlyprogrammingmanipulatorsystems,itdoesnotsolvetheprogrammingproblemitself.Explicitprogrammingofsensor-basedmanipulatorsystemsiscumbersomeduetotheextensiveamountofdetailwhichmustbespecifiedfortherobottoperformthetask.Thesoftwaresynthesisproblemforsensor-basedrobotscanbesimplifieddramatically,byprovidingrobustroboticskills,thatis,encapsulatedstrategiesforaccomplishingcommontasksintherobotstaskdomain.Suchroboticskillscanthenbeusedatthetasklevelplanningstagewithouthavingtoconsideranyofthelow-leveldetails

Asanexampleoftheuseofarapidlydeployablesystem,consideramanipulatorinanuclearenvironmentwhereitmustinspectmaterialandspaceforradioactivecontamination,orassembleandrepairequipment.Insuchanenvironment,widelyvariedkinematic（e.g.,workspace）anddynamic（e.g.,speed,payload）performanceisrequired,andtheserequirementsmaynotbeknownapriori.Insteadofpreparingalargesetofdifferentmanipulatorstoaccomplishthesetasks—anexpensivesolution—onecanusearapidlydeployablemanipulatorsystem.Considerthefollowingscenario:

assoonasaspecifictaskisidentified,thetaskbaseddesignsoftwaredeterminesthetask.ThisoptimalconfigurationisthenassembledfromtheRMMSmodulesbyahumanor,inmanipulator.Theresultingmanipulatorisrapidlyprogrammedbyusingthesoftwareassemblyparadigmandourlibraryofroboticskills.Finally,themanipulatorisdeployedtoperformitstask.

Althoughsuchascenarioisstillfuturistic,thedevelopmentofthereconfigurablemodularmanipulatorsystem,describedinthispaper,isamajorstepforwardtowardsourgoalofarapidlydeployablemanipulatorsystem.

Ourapproachcouldformthebasisforthenextgenerationofautonomousmanipulators,inwhichthetraditionalnotionofsensor-basedautonomyisextendedtoconfiguration-basedautonomy.Indeed,althoughadeployedsystemcanhaveallthesensoryandplanninginformationitneeds,itmaystillnotbeabletoaccomplishitstaskbecausethetaskisbeyondthesystem’sphysicalcapabilities.Arapidlydeployablesystem,ontheotherhand,couldadaptitsphysicalcapabilitiesbasedontaskspecificationsand,withadvancedsensing,control,andplanningstrategies,accomplishthetaskautonomously.

2Designofself-containedhardwaremodules

Inmostindustrialmanipulators,thecontrollerisaseparateunithousingthesensorinterfaces,poweramplifiers,andcontrolprocessorsforallthejointsofthemanipulator.Alargenumberofwiresisnecessarytoconnectthiscontrolunitwiththesensors,actuatorsandbrakeslocatedineachofthejointsofthemanipulator.Thelargenumberofelectricalconnectionsandthenon-extensiblenatureofsuchasystemlayoutmakeitinfeasibleformodularmanipulators.Thesolutionweproposeistodistributethecontrolhardwaretoeachindividualmoduleofthemanipulator.Thesemodulesthenbecomeself-containedunitswhichincludesensors,anactuator,abrake,atransmission,asensorinterface,amotoramplifier,andacommunicationinterface,asisillustratedinFigure3.Asaresult,onlysixwiresarerequiredforpowerdistributionanddatacommunication.

2.1Mechanicaldesign

ThegoaloftheRMMSprojectistohaveawidevarietyofhardwaremodulesavailable.Sofar,wehavebuiltfourkindsofmodules:

themanipulatorbase,alinkmodule,threepivotjointmodules（oneofwhichisshowninFigure2）,andonerotatejointmodule.Thebasemoduleandthelinkmodulehavenodegrees-of-freedom;

thejointmoduleshavedegree-of-freedomeach.ThemechanicaldesignofthejointmodulescompactlyfitsaDC-motor,afail-safebrake,atachometer,aharmonicdriveandaresolver

Thepivotandrotatejointmodulesusedifferentoutsidehousingstoprovidetheright-angleorin-lineconfigurationrespectively,butareidenticalinternally.Figure4showsincross-sectiontheinternalstructureofapivotjoint.EachjointmoduleincludesaDCtorquemotorand100:

1harmonic-drivespeedreducer,andisratedatamaximumspeedof1.5rad/sandmaximumtorqueof270Nm.Eachmodulehasamassofapproximately10.7kg.Asingle,compact,X-typebearingconnectsthetwojointhalvesandprovidestheneededoverturningrigidity.Ahollowmotorshaftpassesthroughalltherotarycomponents,andprovidesachannelforpassageofcablingwithminimalflexing.

2.2Electronicdesign

Thecustom-designedon-boardelectronicsarealsodesignedaccordingtotheprincipleofmodularity.EachRMMSmodulecontainsamotherboardwhichprovidesthebasicfunctionalityandontowhichdaughtercardscanbestackedtoaddmodulespecificfunctionality.

ThemotherboardconsistsofaSiemens80C166microcontroller,64KofROM,64KofRAM,anSMCCOM20020universallocalareanetworkcontrollerwithanRS-485driver,andanRS-232driver.ThefunctionofthemotherboardistoestablishcommunicationwiththehostinterfaceviaanRS-485busandtoperformthelowlevelcontrolofthemodule,asisexplainedinmoredetailinSection4.TheRS-232serialbusdriverallowsforsimplediagnosticsandsoftwareprototyping.

Astackingconnectorpermitstheadditionofanindefinitenumberofdaughtercardswithvariousfunctions,suchassensorinterfaces,motorcontrollers,RAMexpansionetc.Inourcurrentimplementation,onlymoduleswithactuatorsincludeadaughtercard.Thiscardcontainsa16bitresolvertodigitalconverter,a12bitA/Dconvertertointerfacewiththetachometer,anda12bitD/Aconvertertocontrolthemotoramplifier;

wehaveusedanofthe-shelfmotoramplifier（GalilMotionControlmodelSSA-8/80）todrivetheDC-motor.Formoduleswithmorethanonedegree-of-freedom,forinstanceawristmodule,morethanonesuchdaughtercardcanbestackedonto由es创nemotherboard.

3Integratedquick-couplingconnectors

Tomakeamodularmanipulatorbereconfigurable,itisnecessarythatthemodulescanbeeasilyconnectedwitheachother.Wehavedevelopedaquick-couplingmechanismwithwhichasecuremechanicalconnectionbetweenmodulescanbeachievedbysimplyturningaringhandtight;

notoolsarerequired.AsshowninFigure5,keyedflangesprovidepreciseregistrationofthetwomodules.Turningofthelockingcollaronthemaleendproducestwodistinctmotions:

firstthefingersofthelockingringrotate（withthecollar）about22.5degreesandcapturethefingersontheflanges;

second,thecollarrotatesrelativetothelockingring,whileacammechanismforcesthefingersinwardtosecurelygripthematingflanges.Aball-transfermechanismbetweenthecollarandlockingringautomaticallyproducesthissequenceofmotions.

Atthesametimethemechanicalconnectionismade,pneumaticandelectronicconnectionsarealsoestablished.Insidethelockingringisamodularconnectorthathas30male