外文翻译--一种全方位移动机器人的控制设计 英文版.pdf

AbstractAmobilelaboratorywasdevelopedforstudentsoftheECE5320MechatronicsandECE7750DistributedControlSystemscoursesatUtahStateUniversity.Aserialserverwasconnectedtotheembeddedcontrollerofastand-alone3-axesroboticwheelassembly.Thisenabledcommunicationbetweenthewheelandanyinternet-enabledcomputer.Atelepresencecontrolsystemandaprototypenetworkedcontrolsystem(NCS)weredevelopedandtested.Thissystemwassuitablymodifiedtoaccommodatetheneedsofthecourselaboratories,therebyenablingstudentstodesign,debugandtesttheirlaboratoryprojectsinreal-timeattheirchosentimeandlocations.Afully-functionaldemonstrationofthisremotelaboratoryisavailablefrom:http:/www.csois.usu.edu/people/smartwheel/CompleteInfoPage.htmI.INTRODUCTIONAPIDstridesintheuseoftelepresencesystemsfordistancelearningandremoteexperimentationpurposeshaveresultedthroughproliferationoftheInternet,advancesinmobilecommunicationstechnologyandavailabilityofhigh-speedcomputers.ThesedevelopmentshavealsogreatlybenefitedthefieldofControlSystemseducationandproprietaryplatformslikeNationalInstrumentsLabVIEW1andQuansersWinconhavebeenusedinteachinglaboratories.TheDepartmentofElectrical&ComputerEngineeringatUtahStateUniversityoffersagraduate-levelcourseinDistributedControlSystems2.Thiscoursedealswiththedesign,implementationandstabilityissuesinnetworkedcontrolsystems,wirelesssensornetworks,anddistributedparametersystems.ThedepartmentalsooffersacourseinMechatronics3,whichdealswiththeprinciples,interfacing,andsignal-conditioningofmotionsensorsandactuators,themodeling,analysis,andidentificationofdiscrete-timesystems,andManuscriptreceivedSeptember14,2005.YangQuanChenisActingDirector,CenterforSelf-OrganizingandIntelligentSystems,andAssistantProfessor,DepartmentofElectricalandComputerEngineering,UtahStateUniversity,Logan,UT84322USA(phone:435-797-0148；fax:435-797-3054；e-mail:yqchenece.usu.edu).BharathRamaswamywasGraduateResearchAssistantatCenterforSelf-OrganizingandIntelligentSystems,DepartmentofElectricalandComputerEngineering,UtahStateUniversity,Logan,UT84322USA.HeisnowEngineeratQualcommIncorporated,SanDiego,CA92121USA(e-mail:bharath.ramaswamyqualcomm.com).KevinMoorewasDirector,CenterforSelf-OrganizingandIntelligentSystems,UtahStateUniversity,Logan,UT84322USA.HeisnowtheG.A.DobelmanDistinguishedChairandProfessorofEngineering,DivisionofEngineering,ColoradoSchoolofMines,GoldenCO80401USA(e-mail:kmooremines.edu).digitalcontrollerdesignmethods.Thispaperdescribesalow-costremotelaboratorysolutiondevelopedatUtahStateUniversityfortheMechatronicsandDistributedControlSystemscourses.Thepaperisorganizedintoeightsections.Section-IIaddressestheneedforaremotelaboratoryfromapedagogicalperspective.Section-IIIgivesbackgroundinformationonthe“SmartWheel”systemwhichistheplanttobecontrolledduringthelaboratorysessions.Section-IVprovidestheobjectivesandoverallstructureofthecourselaboratory.Section-Vdescribesthehardwareandsoftwarearchitectureofthesystem.Section-VIprovidesdetailsonhowastudentofthecoursecanperformthelaboratory“on-the-go”.Finally,Section-VIIandSection-VIIIsummarizetheresultsandoutlinesfutureprojectgoals.II.PEDAGOGICALMOTIVATIONItisimperativethatengineeringcoursesespeciallythoseintheareaofcontrolsystemsincludeahands-onlaboratorycomponenttoextendtheclassroomexperience.However,thesetup,operationandmaintenanceoflaboratoryequipmentbecomeresource-intensive,time-consumingandexpensive.Virtuallaboratoriesofferacost-effectivealternative；howevertheyoftenfailtomodelthepracticaleffects,andcannotsubstituteforexperiencewiththerealsystem.Remotelaboratoriesofferdistinctadvantagesoverconventionalandvirtuallaboratories.Apartfromcost-reduction,moreefficientusageoflaboratoryequipment,reducedmaintenance,flexibleandself-pacedlearning,thereistheabilitytogivestudentsthesamekindofexperiencetheywouldordinarilyobtaininatraditionallaboratorysettingwithuseofversatile,real-worldequipment.Aremotelearningapplicationcalled“SecondBesttoBeingThere"(SBBT)wasdevelopedatOregonStateUniversity4.Thissolutionincorporatesseveralfeaturessuchasdata-collectionfacility,livevideoandaudiostreaming,safetyandstabilitymeasures,regulationofaccess,andcollaborationsupportallofwhichmaketheremotelaboratoryapleasantandimmersiveexperienceforthestudent.III.PLANTBACKGROUNDINFORMATIONTheCenterforSelf-OrganizingandIntelligentSystemsOmni-directionalRoboticWheel-AMobileReal-TimeControlSystemsLaboratoryBharathRamaswamy,YangQuanChenandKevinMooreRProceedingsofthe2006AmericanControlConferenceMinneapolis,Minnesota,USA,June14-16,2006WeI21.51-4244-0210-7/06/$20.00©2006IEEE719(CSOIS)atUtahStateUniversityhasdesignedanddevelopedseveralprototyperoboticvehiclesbasedonakeyenablingconceptcalledthe“SmartWheel.”Itisaself-containedroboticwheelmodulewith3independentaxesnamelythesteeringaxis,thedriveaxis,andthez-axis.Whenmultiplesmartwheelsareattachedtoachassis,theresultingvehicleiscalledanomni-directionalvehicle5.CSOIShasastand-alonesmartwheelassembly(showninfig.1)equippedwithsteeringanddrivemotors,alinearactuatorforz-axismovement,drivecircuitryforthemotorsandactuator,encodersfordriveandsteeringfeedback,amicrocontroller,andapowerdistributionunit.Thesmartwheelassemblywasmodifiedandaugmentedforuseinthetwocoursesmentioned.Theintendedoutcomesweretoenablestudentstodesignandtesttheirowncontrollersforthesteeringanddriveaxesofthewheel.Theassemblyalsodoublesupasademonstrationsystem6toshowcasethecapabilitiesofthesmartwheeltovisitors,insituandvisitorstotheCSOISwebsite.IV.SYSTEMOVERVIEWA.IntroductiontotheLaboratorySincebothcoursesmentionedearlierincludeastudyofnetworkedcontrolsystems(atvaryinglevels),itwasnecessarytodevelopalaboratorycomponentinordertoaugmenttheclassroomtheory.Anetworkedcontrolsystemisafeedbackcontrolsysteminwhichthecontrolloopisclosedthroughacommunicationnetwork7.Itisimperativethatremoteexperimentationbeusedforthislaboratory.Inthiscase,theplantandfeedback-sensorissituatedinsidetheuniversitysresearchcenter,thecontrollerislocatedontheremotestudentscomputer,andthecommunicationnetworkistheIPnetworkbetweentheplant/sensorandthecontroller.However,dedicatedequipmentforsuchaspecializedlaboratoryisexpensiveandplanningandinstallationistime-consuming.Alow-costsolution,inwhichaserialserverwasusedtomakethesmart-wheelassemblyteleoperable,wasconceivedandimplemented.B.DistributedControlSystemsDesignLaboratoryInthiscourse,thestudentisexpectedtodesignandtestanetworkedcontrolsystemforthesteeringaxisofthesmartwheel.Theserialport(RS232)onthesmartwheelsembeddedcontrollerwasconnectedtoanEthernetHubviaaSerialServer,whichtranslatesmessagesbetweenEthernetandRS232formats.Themicrocontrolleronthewheelwasprogrammedtopollthepositionencoderandtransmitthesevaluesthroughitsserialport.Italsoacceptsvelocityvaluesviatheserialportandconvertsitintopulsewidthmodulated(PWM)signalstodrivethemotor.ThestudentwiththeInternet-enabledcomputeratanyremotelocationwillinstallavirtualCOMdriver,inordertocommunicatewiththesmartwheelsserialserver.Hecandevelophiscontrollerprogramonthecomputer,whichwilltransmitvelocityvaluestothesmartwheel,calculatedbasedontheencoderreadingsreceivedfromthesmartwheel.TheInternetintroducesrandomtimedelaysandperturbations.Thesenetwork-inducedeffectsneedtobetakenintoconsiderationwhiledesigningthecontroller,throughtheuseofsuitabletechniquessuchasnetworkpredictionanddelay-compensation.Theperformanceofthecontrolsystemcanbeexamined,byparsingandplottingtheencoderdataontheremotecomputer.Anywindows-basedenvironmentmaybeusedfordevelopment.Fig.2showstheuser-interfaceforaprototypenetworkedcontrolsystemimplementedforthesteeringaxisofthesmartwheeldevelopedinVisualBasic.Theset-point(steeringangle)andcontrollergains(PIDcontroller)areuser-selectableandtheusercanviewthesystemperformancebyobservingtheangularpositionplotthatappearsinreal-timeonthegraphicaldisplay.AnInternetcamerastreaminglivevideoandaudioenablesthestudenttoviewandhearthewheelmotioninreal-timeonthecontrolpanel.C.MechatronicsDesignProjectLaboratorySincethisisacourseattheundergraduate-level,thestudentscandesignandtestsimplePIDnetworkedcontrollersforthesteeringanddriveaxesontheirinternet-enabledcomputers,butwithoutconsideringnetwork-inducedeffectsintotheirdesign.ItisproposedtoextendtheuseofthesmartwheelassemblyfortheMechatronicscourseintheyear2006.Fig.1.SmartWheelAssemblyonaMobileRig.720D.DemonstrationSystemThemicrocontrolleronthesmartwheelalsohasitsownsetofcontrolalgorithmsforthesteering,driveandz-axes.Inthiscase,themicrocontrolleracceptsset-pointsfromapairofjoysticksortheremotecomputerforeachofthethreeaxesandcontrolsthewheelaccordingtoitson-boardcontrolprogram.ThisfeatureenablesthecapabilitiesofthewheeltobeshowcasedtovisitorsinsituandvisitorstotheCSOISwebsitewhenthewheelisnotbeingusedforthecourselaboratories.Fig.3showstheuser-interfaceforthesmartwheelstelepresencecontrolsystem.Suitablehandshaking,controlandarbitrationprotocolscoordinatebetweenjoystick,telepresenceandnetworkedcontrolmodes,andalsoensurepredictablebehaviorwhenmultipleusersattempttoaccessthesystem.V.SYSTEMDESCRIPTIONA.ArchitectureThearchitectureofthestand-alonesmart-wheeldemonstrationsystem6isshowninfig.4.Thesteeringmotor,drivemotor,andlinearactuatorcontrolthesteeringaxis,driveaxis,andz-axisofthesmartwheel,respectively.ThesteeringanddrivemotorsarecontrolledbyPWManddirectionsignalsfromtheirrespectivemotordrivers.Thesteeringmotoriscoupledtoanabsoluteencoder,whichmeasurestheabsoluteangularpositionofthewheel.Thedrivemotorisattachedtoaquadratureencoderthatmeasurestherelativemotionofthewheel.Thelinearactuatormovestheentiresteeringcolumnupordownalongthelinearslide.Thelinearpotentiometerprovidesfeedbackaboutthez-positionofthesteeringcolumn.Thez-axiscontrolboxcommandsthelinearactuatorbasedonthevoltagevaluefromthedigital-to-analogconverter(DAC)andthefeedbackfromthelinearpotentiometer.ThewheelnodedigitalinterfaceboardconsistsoftheTattletaleModel8(TT8),amicrocontrollerbyOnsetComputerCorporation8basedonMotorolasMC68332microprocessor.Italsoprovidesinterfacesforserialcommunication,motordrivers,DAC,absoluteandquadratureencoders,circuitsforpowersupplyandregulation,level-shifting,andopticalisolation,andthehardwarewatchdogunit.Thesteeringanddrivemotorsareeachdrivenbya50A8DDSeriesPWMservoamplifier(ormotordriver)fromAdvancedMotionControls.Thedutycycleofthepulsewidthmodulated(PWM)signalsdeterminesthespeedofthemotorandlogiclevelofthedirectionsignaldeterminesthedirectionofrotation.Fig.2.Screen-shotofthePrototypeNetworkedControlSystemApplication.Fig.4.SmartWheelSystemOverview.Fig.3.Screen-shotoftheTelepresenceControlSystemApplication.721Twojoystickshavebeenprovidedinordertoenablevisitorstocontrolthe3-axesofthewheelinsitu.Duringthistime,thesystemissaidtobeinJoystickmode.Oneofthem(Joystick-1)isa3-axisjoystickwhereinthex-axisisusedtosetthedrivespeedandthetwistaxisisusedtosetthesteeringspeed.Anothersingle-axisjoystick(Joystick-2)isusedtosetthez-axisposition.Theremoteoperatorcommunicateswiththesmartwheelthroughadeviceknownastheserialserver,whichconvertsmessagesfromRS232formatintoEthernetformatandvice-versa.TheDE-311serialserverfromMoxaTechnologieswasselectedforuseinthesystem9onaccountofitslow-cost,easy-to-installsoftwaredrivers,andthroughput(50bpsto230.4Kbps).ADLinkDCS5300Internetcamera10locatednearthesmart-wheelassemblydirectlysendsstreamingvideo(upto30fpsat640*480resolution)andaudioofthesmartwheelmotiontotheremoteoperator.Itallowsupto20userstoviewthelabactivitywhileonlyoneofthemisinteractingwiththeplant.TheremoteoperatorcancommunicatewiththesystemeitherinTelepresencemode,duringwhichtheon-boardcontrolalgorithmonthewheelcontrolsthe3-axesofthewheelbasedonset-pointsreceivedfromtheremotecomputer；orinNetworkedControlSystemLaboratorymode,duringwhichthecontrolalgorithmontheremotecomputercommandsthewheelsaxesbasedonsampledencode-feedbackreadingsreceivedfromthemicrocontrolleronthewheel.B.MechanicalHardwareDescriptionAcross-sectionalviewofthesmart-wheelassembly(withoutz-axisactuatorfeatures)isshowninfig.5.Thesteeringsuspensionsupportstheentiresteeringmechanismandwheelelectronicsystems.Thesteeringspindleisdirectlycoupledtothesteeringmotor.Theyokefastensthedriveassemblytothesteeringspindle.Theyokealsohousesthepowerandcommunicationscables,whichgodowntothewheel.Acustomslipringallowsinfiniterotationofthewheelaboutthesteeringaxis.Theentiredriveassemblyincludingthedrivespindle,motor,failsafebrake,andencoderisenclosedinsidethewheelshell.ThedrivemotorisaKollmorgenmodelQT-6407framelesstorquermotorandthesteeringmotorisaMicroMoseriesGNM5440PMDCmotor.ACP-560quadratureencoderfromComputerOpticalProductsisusedtomeasurerelativewheelposition.Theabsoluteencoderusedtomeasureabsoluteangularpositionofthesteeringmotorinbody-fixedcoordinatesisaModel40HfromSequentialElectronicSystems.Z-axisactuationcapabilitywasaddedbymountingtheassemblyshowninfig.5onanElectraklinearactuatorfromWarnerElectric.Alinearpotentiometerismountedadjacenttothelinearactuatornearthetop.Thepowerdistributionunitsareenclosedbehindthedamper.Acontrolboxforthez-axismovementismountedononesideofthepowerdistributionunithousing.Thewheelelectronicsandmotordriversaremountedoneithersideofthesteeringcolumn.Theentireassemblyismountedonawheeledstand.Refertofig.1againtoseeacompletepictureofthesystem.C.SoftwareDescriptionSoftwareforthestand-alonesmart-wheeldemonstrationsystemcomprisesthefollowing:-EmbeddedsoftwareontheTT8microcontrollerboard.-VideoandaudiobufferingandstreamingsoftwareontheInternetcameraswebserver.-EmbeddedsoftwareontheserialservertoperformconversionofmessagesbetweenEthernetandRS232formats.-VirtualCOMdriverthatallowscommunicationbetweenthestudentsremotecomputerandtheserialserver.-ApplicationsoftwareforNetworkedControlofthesmartwheelsaxesonthestudentscomputer.Thesoftwarearchitectureofthesystemisdepictedinfig.6.Ofthese,theVirtualCOMdriver(Moxatech.),theserialFig.6.SmartWheelSoftwareArchitecture.Fig.5.SmartWheelMechanicalAssembly.722