毕业设计机械手外文翻译.docx

外文翻译译文题目一种与移动机械臂的局部零件所受载荷相协调的运动结构(2)原稿题目AkinematicallyCOmPatibleframeworkforCOoPeratiVePaylOadtransportbySonholonomicmobilemanipulators(2)原稿出处AUtOnRobot(2006)21:227-242Akinematicallycompatibleframeworkforcooperativepayloadtransportbynonholonomicmobilemanipulators(2)M.Abou-Samah1,C.P.Tang2,R.M.Bhatt2andV.Krovi2(1) MSCSoftwareCorporation,AnnArbor,Ml48105,USA(2) MechanicalandAerospaceEngineering,StateUniversityofNewYorkatBuffalo,Buffalo,NY14260,USAReceived:5August2005Revised:25May2006Accepted:30May2006Publishedonline:5September2006AbstractInthispaper,weexaminethedevelopmentofakinematicallycompatiblecontrolframeworkforamodularsystemofwheeledmobilemanipulatorsthatcanteamuptocooperativelytransportacommonpayload.Eachindividuallyautonomousmobilemanipulatorconsistsofadifferentially-drivenWheeledMobileRobot(WMR)withamountedtwodegree-of-freedom(d.o.f)revolute-jointed,planarandpassivemanipulatorarm.Thecompositewheeledvehicle,formedbyplacingapayloadattheend-effectorsoftwo(ormore)suchmobilemanipulators,hasthecapabilitytoaccommodate,detectandcorrectbothinstantaneousandfiniterelativeconfigurationerrors.Thekinematica11y-compatib1emotion-planning/controlframeworkdevelopedhereisintendedtofacilitatemaintenanceofallkinematic(holonomicandnonholonomic)constraintswithinsuchsystems.Givenanarbitraryend-effectortrajectory,eachindividualmobi1e-manipu1ator,sbi-levelhierarchicalcontrollerfirstgeneratesakinematically-feasibledesiredtrajectoryfortheWMRbase,whichisthentrackedbyasuitablelower-levelposturestabilizingcontroller.Twovariantsofsystem-levelcooperativecontrolschemesleader-followeranddecentralizedcontrolarethencreatedbasedontheindividualmobi1e-manipuIatorcontrolscheme.Bothmethodsareevaluatedwithinanimplementationframeworkthatemphasizesbothvirtualprototyping(VP)andhardware-in-the-loop(HIL)experimentation.Simulationandexperimentalresultsofanexampleofatwo-modulesystemareusedtohighlightthecapabilitiesofareal-timelocalsensor-basedcontrollerforaccommodation,detectionandcorectionofrelativeformationerrors.KeywordsCompositesystem-Hardware-in-the-loop-MobilemanipuIator-Physicalcooperation-Redundancyresolution-VirtualprototypingKinematiccollaborationoftwomobilemanipulatorsWenowexaminetwovariantsofsystem-levelcooperativecontrolschemes-leader-followeranddecentralizedcontrol-thatcanbecreatedbasedontheindividualmobi1e-manipu1atorcontrolscheme.1.eader-followerapproachThefirstmethodofmodelingsuchasystemconsidersthemidpointofthemobilebase(MPB)ofthemobi1e-manipuIatorBtoberigidlyattachedtotheend-effectorofmobilemanipulatorA,asdepictedinFig.4.Figure4(b)depictshowtheend-effectorframe用ofMPAisrigidlyattachedtotheframeatMPB(separatedbyaconstantrotationangle).co0anj3Xg0Yt(15)Fig.4Schematicdiagramsoftheleader-followerscheme:(a)the3-linkmobilemanipulatorunderanalysis,and(b)thetwo-modulecompositesystem(*),玦),g(2),MPBnowtakesontheroleoftheleaderandcanbecontrolledtofollowanytrajectorythatisfeasibleforaWMR.Hence,givenatrajectoryoftheleaderMPBand the preferred manipulator configuration of(" M(e)(5) can be rewritten as:X，_co8XYi=sin/5cob0Y；三inco-rfcc4-in,rfLj+Lcos÷Ljco空1.ISm%+"三nC0Sinyc07-smqi323-Lsin11.11三)÷Ljc03Ljcott0|彳(16)andcorrespondinglyEqs.(6)-(8)as:(17)(部三(2)'+M)'xi-jx(%7rco也Thus,thetrajectoryofthevirtual(reference)robotforthefollowerMPA(Xf,'F",C"Iv<f).u4C),andthederivedvelocitiescannowbedetermined.Thisformstheleader-followerschemeusedforthecontrolofthecollaborativesystemcarryingacommonpayload.DecentralizedapproachThesecondapproachconsiderstheframeattachedtoapointofinterestonthecommonpayloadastheend-effectorframeofboththeflankingmobilemanipulatorsystems,asdepictedinFig.5.Thus,adesiredtrajectoryspecifiedforthispayloadframecanthenprovidethedesiredreferencetrajectoriesforthetwomobileplatformsusingthesimilarframeworkdevelopedintheprevioussectionbytaking人工3=°and0*')°,wherek=A,B.ThispermitsEq.(5)toberewrittenas:气4AilkYieo4-4coV一mVsin/cosFig. 5 Decentralizedcontrolschemeimplementationpermitsthe(a)compositesystem;tobetreatedas(b)twoindependent2-linkmobilemanipulatorsS=慧)，½=(¾),÷ (tvi),kd v 上 W * Yd(k×iVandcorrespondinglyEq.(6)-(8)as:(19)Eachtwo-linkmobilemanipulatornowcontrolsitsconfigurationwithreferencetothiscommonend-effectorframemountedonthepayload.However,thelocationsoftheattachmentsofthephysicalmanipulatorswithrespecttothepayloadreferenceframemustbeknownapriori.ImplementationframeworkWeexaminethedesignanddevelopmentofatwo-stageimplementationframework,showninFig.6,thatemphasizesbothvirtualprototyping(VP)basedrefinementandhardware-in-1he-1oop(HIL)experimentation.Fig. 6 ParadigmforrapiddevelopmentandtestingofthecontrolschemeonvirtualandphysicalprototypesVirtualprototypingbasedrefinementInthefirststage,weemployvirtualprototyping(VP)toolstorapidlycreate,evaluateandrefineparametricmodelsoftheoverallsystemandtestvariousalgorithmsinsimulationwithinavirtualenvironment.3DsolidmodelsofthemobileplatformsandthemanipulatorsofinterestarecreatedinaCADpackage,andexportedwiththeircorrespondinggeometricandmaterialpropertiesintoadynamicsimulationenvironment.Figure7(a)showsanexampleoftheapplicationofsuchframeworkforsimulatingthemotionofamobileplatformcontrolledbyanalgorithmimplementedinSimulink.However,itisimportanttonotethattheutilityofsuchvirtualtestingislimitedby:(a)theabilitytocorrectlymodelandsimulatethevariousphenomenawithinthevirtualenvironment;(b)thefidelityoftheavailablesimulationtools;and(c)ultimately,theabilityofthedesignertocorrectlymodelthedesiredsystemandsuitablyinterprettheresults.Fig. 7 AsingleWMRbaseundergoingtestingwithinthe(a)virtualprototypingframework;and(b)hardware-in-the-loop(HIL)testingframeworkHardware-in-the-loopexperimentationWeemployahardware-in-the-loop(HIL)methodologyforrapidexperimentalverificationofthereal-timecontrollersontheelectromechanicalmobilemanipulatorprototypes.EachindividualWMRisconstructedusingtwopoweredwheelsandtwounactuatedcasters.Conventionaldisc-typerearwheels,poweredbygear-motors,arechosenbecauseofrobustphysicalconstructionandeaseofoperationinthepresenceofterrainirregularities.Passiveballcastersarepreferredoverwheelcasterstosimplifytheconstraintsonmaneuverabilityintroducedbythecasters.Themountedmanipulatorarmhastwopassiverevolutejointswithaxesofrotationparalleltoeachotherandperpendiculartothebaseofthemobileplatform.Thefirstjointisplacedappropriatelyatthegeometriccenterontopframeoftheplatform.Thelocationofthesecondjointcanbeadjustedtoanypositionalongtheslottedfirstlink.Thesecondlinkitselfisreducedtoaflatplatesupportedbythesecondjoint.Eachjointisinstrumentedwithopticalencoderthatcanmeasurethejointrotations.Thecompletelyassembledtwo-linkmobilemanipulatorisshowninFig.1.(c).Thesecondmobilemanipulator(seeleftmoduleofFig.1(b)and(d)employsthesameoveralldesignbutpossessesamotoratthebasejointofthemountedtwo-linkarm.Themotormaybeusedtocontrolthejointmotionalongapredeterminedtrajectory(whichcanincludebraking/holdingthejointatapredeterminedposition).Whenthemotorisswitchedoffthejointnowrevertstoapassivejoint(withmuchgreaterdamping).Themotorisincludedforpermittingfutureforce-redistributionstudies.Inthispaper,however,themotorisusedsolelytolockthejointpreventself-motionsofthearticulatedlinkageforcertainpathologicalcases(Bhattetal.,2005;TangandKrovi,2004).PWrM-OUtputmotordrivercardsareusedtodrivethegearmotors;andencodercardsmonitortheencodersinstrumentingthevariousarticulatedarms.ThisembeddedcontrollercommunicateswithadesignatedhostcomputerusingTCP/IPforprogramdownloadanddatalogging.ThehostcomputerwithMATLAB/Simulink/RealTimeWorkshop"providesaconvenientgraphicaluserinterfaceenvironmentforsystem-levelsoftwaredevelopmentusingablock-diagrammaticlanguage.Thecompiledexecutableisdownloadedoverthenetworkandexecutesinreal-timeontheembeddedcontrollerwhileaccessinglocallyinstalledhardwarecomponents.Inparticular,theabilitytoselectivelytestcomponents/systemsatvariouslevels(e.g.individualmotors,individualWMRsorentiresystems)withoutwearingoutcomponentsduringdesigniterationswasveryuseful.Figure7(b)illustratestheimplementationofsuchasystemononeoftheWMRs.Numerouscalibration,simulationandexperimentalstudiescarriedoutwiththisframework,attheindividual-levelandsystem-level,arereportedinAbou-Scimah(2001).ExperimentalresultsForthesubsequentexperiments,2weprescribetheinitialconfigurationofthetwo-modulecompositesystem,asshowninFig.8.Specifically,wepositionthetwoWMRSsuchthatMPAislocatedatarelativepositionof工一O.OOjdjOin.)y=0.61m124in.,ancjwt1arelativeorientationdifferenceof=0.00owithrespecttoMPB.Forfixedlink-lengthsthisinherentlyspecifiesthevaluesofthevariousconfigurationanglesasshowninTable1.Table1Parametersfortheinitialconfigurationofthetwo-modulecompositewheeledsystem(seeFig.8fordetails)LinklengthsofthearticulationL10.28m(11in)L20.28m(11in)RelativeanglesoftheconfigurationofthearticulationL30.28m(11in)1333.98°2280.07o3337.36oOffsetbetweenthewheeledmobilebases1128.59o0.00oObOax0.00m(0in)0.61m(24in)Fig.8Initialconfigurationofthetwo-modulecompositewheeledsystem1.eader-followerapproachAstraightlinetrajectoryatavelocityof0.0254m/sisprescribedfortheleader,MPB.Givenadesiredconfigurationofthemanipulatorarm,thealgorithmdescribedinSection4.1isusedtoobtainadesiredtrajectoryforMPA.AlargedisruptionisintentionallyintroducedbycausingoneofthewheelsofMPAtorunoverabump,toevaluatetheeffectivenessofthedisturbanceaccommodation,detectionandcompensation.Theresultsareexaminedintwocasescenarios-CaseA:MPAemploysodometricestimationforlocalizationasseeninFig.9,andCaseB:MPAemployssensedarticulationsforIocalizationasseeninFig.10.Ineachofthesefigures,(a)presentstheoveral1(Xu,u)-trajectoryofMofMPAwithrespecttotheend-effectorframe£(thatisrigidlyattachedtothe.ofMPB)while(b),(c)and(d)presenttherelativeorientationdifference,differenceanddifferenceasfunctionsoftime.Furtherinbothsetsoffigures,the'Desired'(-line)isthedesiredtrajectorytypicallycomputedoffline;and*Actual,(-o-line)thesystem,asdeterminedbypost-processingthearticulations.is the actual trajectory followed by measurements of the instrumentedHowever,inFig.9,the(-x-line)representstheodometricestimatewhileinFig.10itFig.9 Ca se A: Odom etric Estim ation ofFrame M, used in the controI of MP A followi(which therefore coincides with the 'Actual'stands for the articulation based estimate后恐Iused for control of MPA J with respect to MP B in a leader-follower approach is able to detect and correct non-systematic errors suchFig. 10ArticulationEstimation ofCase B: based Frame M,g MPBin a leader -follow(d)erapproach,isunabletodetectnon-systematicerrorssuchaswheel-slip,(a)XYtrajectoryofFrameM;(b)OrientationversusTime;(c)XpositionofFrameMversusTime;and(d)YpositionofFrameMversusTimeaswheel-slip,(a)XYtrajectoryofFrameM;(b)OrientationversusTime;(c)XpositionofFrameMversustime;and(d)YpositionofFrameMversustimeInCaseA,theintroductionofthedisruptioncausesadriftintherelativeconfigurationofthesystemwhichremainsundetectedbytheodometricestimation.Further,asseeninFig.9,thisdrifthasatendencytogrowifleftuncorrected.However,asseeninFig.i0,thesystemcanusethearticulation-basedestimation(CaseB)tonotonlydetectdisturbancestotherelativeconfigurationbutalsotosuccessfullyrestoretheoriginalsystemconfiguration.DecentralizedcontrolapproachInthisdecentralizedcontrolscenario,astraightlinetrajectorywithavelocityof0.0254m/sispresentedforthepayloadframe.Asintheleader-followerscenario,alargedisruptionisintroducedbycausingoneofthewheelsofMPAtorunoverabump.ThealgorithmistestedusingtwofurthercasescenariosCaseC:BothmobiIeplatformsemployodometricestimationforlocalizationasshowninFig.1_1,andCaseD:BothmobileplatformsemploysensedarticulationsforlocalizationasshowninFig.2.化、小Fig.11CaseC:OdometricestimationofframesMofMPAandMPB,usedinthecontrolofMPAwithrespecttoMPBinthedecentralizedapproach,isagainunabletodetectnon-systematicerrorssuchaswheel-slip.(a)XYtrajectoryofframeMofMPA;(b)XYtrajectoryofframeMofMPB;(c)Relativeorientation,betweenMPAandMPB,versustime;(d)Xdistance,betweenMPAandMPB,versustime;and(e)Ydistance,betweenMPAandMPB,versustime.(f)Sequentialphotographsofthecorrespondingcompositesystemmotion(astimeprogressesfromlefttorightalongeachrow)Fig.of MP A and MP B with respect to a payload-fixed frame is able to detect and correct non-systematic errors such as wheel-slip, (a) XY trajectory of frame M of MP A; (b) XY trajectory of frame M of MP B; (c) Relative orientation, between MP A and MP B, versus time; (d) X distance, between MP A and MP B, versus time; and (e) Y distance, between MP A and MP B, versus time. (f) Sequential photographs of the corresponding composite system motion (as time progresses from left to right along each row)12CaseD:ArticulationbasedestimaIneachofthesefigures,subplots(a)and(b)presentstheoverall(viVtrajectoriesofframesMofMPAandMPBrespectivelywithrespecttotheirinitialposes.Subplots(c),(d)and(e)presenttherelativeorientationdifference,differenceanddifferenceofframes册ofMPAandMPBrespectivelyasfunctionsoftime.Furtherinbothsetsoffigures,the'Desired'(-line)isthedesiredtrajectorytypicallycomputedoffline;and4Actual,(-o-line)istheactualtrajectoryfollowedbythesystem,asdeterminedbypost-processingthemeasurementsoftheinstrumentedarticulations.However,inFig.LI,the(-x-line)representstheodometricestimatewhileinFig.12itstandsforthearticulationbasedestimate.InCaseC,bothmobileplatformsusetheodometricestimationforlocalization-henceasexpected,Fig.reflectsthefactthatthesystemisunabletodetectorcorrectforchangesintherelativesystemconfiguration.HoweverthedataobtainedfromthearticulationsaccuratelycapturestheexistenceoferrorsbetweentheframesofreferenceofMPBandMPA.Thus,usingthearticulation-basedestimationofrelativeconfigurationforcontrolasinCaseDallowsthedetectionofdisturbancesandsuccessfulrestorationoftheoriginalsystemconfigurationasshowninFig.12.Note,however,whiletherelativesystemconfigurationismaintained,errorsrelativetoaglobalreferenceframecannotbedetectedifbothWMRSundergoidenticalsimultaneousdisturbances.Detectionofsuchabsoluteerrorswouldrequireanexternalreferenceandisbeyondthescopeoftheexistingframework.ConclusionInthispaper,weexaminedthedesign,developmentandvalidationofakinematicallycompatibleframeworkforcooperativetransportofacommonpayloadbyateamofnonholonomicmobilemanipulators.EachindividualmobilemanipulatormoduleconsistsofadifferentiallydrivenwheeledWMRretrofittedwithapassivetworevolutejointedplanarmanipulatorarm.Acompositemultidegree-Of-freedomvehiclesystemcouldthenbemodularIycreatedbyattachingacommonpayloadontheend-effectoroftwoormoresuchmodules.Thecompositesystemallowedpayloadtrajectorytrackingerrors,arisingfromsubsystemcontrollererrorsorenvironmentaldisturbances,tobereadilyaccommodatedwithinthecomplianceofferedbythearticulatedlinkage.TheindividualmobilemanipulatorscompensatedbymodifyingtheirWMRbases,