毕业设计机械手外文翻译.doc

毕业设计机械手外文翻译.doc

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外文翻译

译文题目一种与移动机械臂的部分零件所受载荷相协调的运动结构

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原稿题目Akinematicallycompatibleframeworkforcooperativepayloadtransportbynonholonomicmobilemanipulators

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原稿出处AutonRobot（2006）21:

227–242

Akinematicallycompatibleframeworkforcooperativepayloadtransportbynonholonomicmobilemanipulators

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M. Abou-Samah1 ,C. P. Tang2 ,R. M. Bhatt2 andV. Krovi2 

（1） MSCSoftwareCorporation,AnnArbor,MI 48105,USA

（2） MechanicalandAerospaceEngineering,StateUniversityofNewYorkatBuffalo,Buffalo,NY 14260,USA

Received:

5 August 2005  Revised:

25 May 2006  Accepted:

30 May 2006  Publishedonline:

5 September 2006

Abstract  Inthispaper,weexaminethedevelopmentofakinematicallycompatiblecontrolframeworkforamodularsystemofwheeledmobilemanipulatorsthatcanteamuptocooperativelytransportacommonpayload.Eachindividuallyautonomousmobilemanipulatorconsistsofadifferentially-drivenWheeledMobileRobot（WMR）withamountedtwodegree-of-freedom（d.o.f）revolute-jointed,planarandpassivemanipulatorarm.Thecompositewheeledvehicle,formedbyplacingapayloadattheend-effectorsoftwo（ormore）suchmobilemanipulators,hasthecapabilitytoaccommodate,detectandcorrectbothinstantaneousandfiniterelativeconfigurationerrors.

Thekinematically-compatiblemotion-planning/controlframeworkdevelopedhereisintendedtofacilitatemaintenanceofallkinematic（holonomicandnonholonomic）constraintswithinsuchsystems.Givenanarbitraryend-effectortrajectory,eachindividualmobile-manipulator'sbi-levelhierarchicalcontrollerfirstgeneratesakinematically-feasibledesiredtrajectoryfortheWMRbase,whichisthentrackedbyasuitablelower-levelposturestabilizingcontroller.Twovariantsofsystem-levelcooperativecontrolschemes—leader-followeranddecentralizedcontrol—arethencreatedbasedontheindividualmobile-manipulatorcontrolscheme.Bothmethodsareevaluatedwithinanimplementationframeworkthatemphasizesbothvirtualprototyping（VP）andhardware-in-the-loop（HIL）experimentation.Simulationandexperimentalresultsofanexampleofatwo-modulesystemareusedtohighlightthecapabilitiesofareal-timelocalsensor-basedcontrollerforaccommodation,detectionandcorectionofrelativeformationerrors.

Keywords  Compositesystem-Hardware-in-the-loop-Mobilemanipulator-Physicalcooperation-Redundancyresolution-Virtualprototyping

Kinematiccollaborationoftwomobilemanipulators

Wenowexaminetwovariantsofsystem-levelcooperativecontrolschemes—leader-followeranddecentralizedcontrol—thatcanbecreatedbasedontheindividualmobile-manipulatorcontrolscheme.

Leader-followerapproach

Thefirstmethodofmodelingsuchasystemconsidersthemidpointofthemobilebase（MPB）ofthemobile-manipulatorBtoberigidlyattachedtotheend-effectorofmobilemanipulatorA,asdepictedinFig.4.Figure4（b）depictshowtheend-effectorframe{E}ofMPAisrigidlyattachedtotheframeatMPB（separatedbyaconstantrotationangleβ）.

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Fig.4 Schematicdiagramsoftheleader-followerscheme:

（a）the3-linkmobilemanipulatorunderanalysis,and（b）thetwo-modulecompositesystem

MPBnowtakesontheroleoftheleaderandcanbecontrolledtofollowanytrajectorythatisfeasibleforaWMR.Hence,givenatrajectoryoftheleaderMPB,andthepreferredmanipulatorconfigurationof,Eq.（5）canberewrittenas:

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andcorrespondinglyEqs.（6）–（8）as:

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Thus,thetrajectoryofthevirtual（reference）robotforthefollowerMPA,andthederivedvelocitiescannowbedetermined.Thisformstheleader-followerschemeusedforthecontrolofthecollaborativesystemcarryingacommonpayload.

Decentralizedapproach

Thesecondapproachconsiderstheframeattachedtoapointofinterestonthecommonpayloadastheend-effectorframeofboththeflankingmobilemanipulatorsystems,asdepictedinFig.5.Thus,adesiredtrajectoryspecifiedforthispayloadframecanthenprovidethedesiredreferencetrajectoriesforthetwomobileplatformsusingthesimilarframeworkdevelopedintheprevioussectionbytakingand,where.ThispermitsEq.（5）toberewrittenas:

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Fig.5 Decentralizedcontrolschemeimplementationpermitsthe（a）compositesystem;tobetreatedas（b）twoindependent2-linkmobilemanipulators

andcorrespondinglyEq.（6）–（8）as:

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Eachtwo-linkmobilemanipulatornowcontrolsitsconfigurationwithreferencetothiscommonend-effectorframemountedonthepayload.However,thelocationsoftheattachmentsofthephysicalmanipulatorswithrespecttothepayloadreferenceframemustbeknownapriori.

Implementationframework

Weexaminethedesignanddevelopmentofatwo-stageimplementationframework,showninFig.6,thatemphasizesbothvirtualprototyping（VP）basedrefinementandhardware-in-the-loop（HIL）experimentation.

Fig.6 Paradigmforrapiddevelopmentandtestingofthecontrolschemeonvirtualandphysicalprototypes

Virtualprototypingbasedrefinement

Inthefirststage,weemployvirtualprototyping（VP）toolstorapidlycreate,evaluateandrefineparametricmodelsoftheoverallsystemandtestvariousalgorithmsinsimulationwithinavirtualenvironment.3DsolidmodelsofthemobileplatformsandthemanipulatorsofinterestarecreatedinaCADpackage,4andexportedwiththeircorrespondinggeometricandmaterialpropertiesintoadynamicsimulationenvironment.5Figure7（a）showsanexampleoftheapplicationofsuchframeworkforsimulatingthemotionofamobileplatformcontrolledbyanalgorithmimplementedinSimulink.6However,itisimportanttonotethattheutilityofsuchvirtualtestingislimitedby:

（a）theabilitytocorrectlymodelandsimulatethevariousphenomenawithinthevirtualenvironment;（b）thefidelityoftheavailablesimulationtools;and（c）ultimately,theabilityofthedesignertocorrectlymodelthedesiredsystemandsuitablyinterprettheresults.

Fig.7 AsingleWMRbaseundergoingtestingwithinthe（a）virtualprototypingframework;and（b）hardware-in-the-loop（HIL）testingframework

Hardware-in-the-loopexperimentation

Weemployahardware-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（Bhattet al.,2005;TangandKrovi,2004）.

PWM-outputmotordrivercardsareusedtodrivethegearmotors;andencodercardsmonitortheencodersinstrumentingthevariousarticulatedarms.ThisembeddedcontrollercommunicateswithadesignatedhostcomputerusingTCP/IPforprogramdownloadanddatalogging.ThehostcomputerwithMATLAB/Simulink/RealTimeWorkshop8providesaconvenientgraphicaluserinterfaceenvironmentforsystem-levelsoftwaredevelopmentusingablock-diagrammaticlanguage.Thecompiledexecutableisdownloadedoverthenetworkandexecutesinreal-timeontheembeddedcontrollerwhileaccessinglocallyinstalledhardwarecomponents.

Inparticular,theabilitytoselectivelytestcomponents/systemsatvariouslevels（e.g.individualmotors,individualWMRsorentiresystems）withoutwearingoutcomponentsduringdesigniterationswasveryuseful.Figure7（b）illustratestheimplementationofsuchasystemononeoftheWMRs.Numerouscalibration,simulationandexperimentalstudiescarriedoutwiththisframework,attheindividual-levelandsystem-level,arereportedinAbou-Samah（2001）.

Experimentalresults

Forthesubsequentexperiments,9weprescribetheinitialconfigurationofthetwo-modulecompositesystem,asshowninFig.8.Specifically,wepositionthetwoWMRssuchthatMPAislocatedatarelativepositionof,andwitharelativeorientationdifferenceofwithrespecttoMPB.

Forfixedlink-lengthsthisinherentlyspecifiesthevaluesofthevariousconfigurationanglesasshowninTable1.

Table1