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Wheeled foot quadruped robot HITAN-I

By Diane Gonzalez,2014-08-06 13:47
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Wheeled foot quadruped robot HITAN-I

    Wheeled foot quadruped robot HITAN-I HIGHTECHNOIDGYI'ERSlVn1.12No.4IDec.2O06

    WheeledfootquadrupedrobotHITAN-I?

    WangPengfei(王鹏飞)?,SunLining

    (RoboticsInstitute,HarbinInstituteofTechnology,Harbin150001,P.R.China) Inviewoftherobotrunningenvironment,thestructureofwheeledfootandquadrupedareadopted

    inthisrobotsystem,whichcombinestheprioritiesofbothwheeledrobotandleggedrobot.BasedonCAN

    bus.thetwo.classrobotcontmlsystemusingmultiplecontrollersanddriversisconstructed.Atthesame

    time,serialinversekinematicsofswayinglegandparallelinversekinematicsofsupportinglegsalearia-

    lyzedindependently.Theforwardgaitandturninggaitgleeplannedandexperimentimageisgivenatlast.

    Keywords:wheeledfoot,robot,contro1system,gaitplanning

    Inthepast.muchworkhasbeendonetoinvestigate

    four-leggedwalking.TwooftheearliestworksaretheG.

    E.QuadrupedandPhoneyL11.Withtheintroductionof

    molepowerfulcomputers,moreandmorebionicrobots

    havebeeninventedinrecentyears.WARPlin2002,

    TITAN[3-5]from1989.

    BISAM[6]in1998andSCOUT

    IIL71in1999al'eexamplesforthesedevelopments.As

    groundvehicle,theadvantagesofmobilerobothavebeen

    recognizedbypeopleinengineeringfields.Groundmobile

    robotsareusuallyclassifiedintotwotypes.wheeledrobot

    andleggedrobot.Leggedrobotisprovidedwithmore flexibilityoverwheeledrobotinbumpyenvironmentsas dene.marish,massifandsoon.However,wheeledrobot possesseshigherspeedthanleggedrobotonceintheenvi

    ronmentofevenness.Inviewoftherobotrunningenvi. ronment,thestructureofmulti.motionmode,fourlegs andwheeledfootsareadoptedinthisvehiclesystem.This robotCallwellcombinetl1eprioritiesofwheeledrobotand leggedrobot,changemotionmodetostablewalkingor fastwheeleddrivingaccordingtodifferentenvironments, sobothflexibilityandhigherspeedarerealized.Such robotstructurecanbecomeagoodplatfore1forapplication ofmedicalservices,environmentalmonitoring,terrorism prevention,andotherrelatedareas.

    Fig.1showsthemechanicalstructureofthemulti

    motionmodequadrupedbionicrobot.Therobot,weighed 2Okg,consistsoffiveindependentparts:fourlegsand onebody.Accordingtodifferentroadsurfaces,themo- bilespeedcanreachupto0.1m/sonlegdrivingand0.8 m/sonwheeldriving.Atthesanletime,therobotisable toidentitynavigationmarkandaccordinglyadoptsmoving strategy.Thereale4DOFsineachlegofrobot.thatisa joint(synchronousstrapdrive)andjoint(worn]gear

    drive)incoaxposition,7ioint(wormgeardrive)inknee positionanddrivingwheelatthefootofleg.Whenrobot movesinlegdrivingstatejuttingoutitslegtoeachside (seeFig.1),thedrivingwheelislockedwitheleetromag- neticrelay,thenthewheelsal'edeemedasfeet.Theno

    torsinajoint,jointand7jointaledrivenincertaindi- rection.Whenrobotmovesinwheeldrivingstate,thea

joint,jointand7jointalelockedwithmotorautolock

    functionandelectromagneticrelayreleases.Wheelsdrive therobotmovinginhighspeedlikewheeledrobot. Fig.1Mechanicalstructure

    Asonekindofleggedvehicle,thequadrupedrobot notonlyismultijointmechanical,but.alsohasever

    changingkinematicstopology.SoitisimpossibletoanD_

    lyzeitskinematicsasawhole.Whenrobotmovesin ?SupportedbytheHT}ml0

    ResearchandDevelopmentPro~amnleofChina(2004AA420110)andthe~ientificResearc

    hFoundationofHei.

    1on~iangProvince(CBO4A502).

    ?Towhomcorrespondenceshouldbeaddressed.E.mail:wpflaust@sohu.con

    ReceivedonJuly29,2005

HIGHTECHNOIJ.lGYI.RSIVo1.12No.4IDec.2006347

    walkingstatewithdutyfactor=0.75,itsthreelegs supportitsbodytomoveforwardandthefourthlegsways inthesanledirection.Soineveryquarterofacycle,the swayinglegcanberegardedasserialarm-and-handsys

    temfixedonmovingfoundationandthesupportinglegs, bodyandgroundcanberegardedas3-RRRSparallelme

    chanicalofsixDOF.Ofcourse,theconditionisthatthe contactpointsbetweenwheelsandgroundareregardedas spherejoints.Soserialinversekinematicsofswayingleg andparallelinversekinematicsofsupportinglegscanbe analyzedindependently.

    2.1Serialinversekinematicsanalysisofswayingleg Fig.2showsthesimplifiedstructure,coordinates andgeometricparametersforanalysisconvenience.Oxyz

istheglobalcoordinate.ocisthebodycoordinate

    andOcislocatedinthecenterofrobotbody.Reference coordinateOoxoYoZocoincideswithO1x1Y11. D11y1Zl,02x2Y2Z2,03x3YaZ3arejointcoordinates whicharesetupaccordingtoD-Hmethod.DHparame-

    tersforserialkinematicsanalysisareshowedintable1. /.--380.Omm

    Fig.2Coordinatesystemofrobot

    natevaluesare,Y,Zinreferencecoordinateand(0, d2,0)incoordinate03x3y33respectively.Thenweget equation

    o

    3*

    0

    d2

    0

    l,

    Z

    l

    Sotheserialinversekinematicsforswayinglegcan beresolvedfromEq.(1)asfollows

    01=arctgY(2)

    d2(d2mn+a2.)

    01=arcsin2a2d2

    +arctg()

    ~/m2+n2

    (3)

    arcsin(4)

    where=COS01+YsinO1al'n=Z+d1

    2.2Parallelinversekinematicsofsupportinglegs

    Asstatedabove,whenrobotbodymovesforward withthreesupportinglegs,thesupportinglegs,bodyand groundcallberegardedas3RRRSparallelmechanicalof

    sixDOFs.Parallelinversekinematicsanalysisisrelative- lysimple.SupposethatRi.(i=14)iscoordinates

    vectorofot1ointinbodycoordinatesocz..Qlointsale expressedasA(n=14)inFig.2.Coordinatesvector

    RofApointinglobalcoordinateOxyzcanbederivedby followingequation

    R=TR+P(5)

    whereTistransformmatrixoforelativetoOxyz. PiscoordinatevectorofOcrelativetoOxyz.Ifthere- quiredpostureandmotionofrobotbodyaleknown,trans

    formmatrixTofD.comparetoOxyzisalsoknown.

    S0ApointcoordinatesvectorRinglobalcoordinates OxyzcanbederivedfromEq.(5).Sotherelativeposi

    tionrelationsbetweenpointAnandpointBnisknown. T——

    a

    

    ble

    ——

    1D-HparametersofonelegSubsequentlywecanapplyaboveserialinversekinematics

    analysisresultandgetninejoints'turningdegreefor reachingtherequiredpostureandmotion.Detailedcalcu

    lationisomittedinthispaper.

    BysubstitutingparametersinTable1intoD--Hma-- trix,wegetthreetransformingmatrixes.T1,,2T3Theoreticallythetotalnumberofpossiblega

    itevent

    betweentwoadjacentjoints.Sothewholetransforming

    matrix0T3betweenO00Y0z0andO33Y33canbede. rivedby.T3=0T1IT22T3.

    SupposethatthewheelpointB(n=1(4)coordi

    sequencesforaquadrupedis5040,butonlyaverysmall portionofthemaresuitableflsgaitsandusedbyanimals (McGheeandFrank,1968).Mostpeoplearefamiliar withthenamesofsomeofthesegaits,forinstance,a horsewillswitchbetweendifferentgaitswhenincreasing

348HIGHTECHNOLOGYIERSIVo1.12No.4IDec.2O06

    speed,firstwalk,thentrot,thencanter,andfinally 1op.Aquadrupedgaithasexactlyeighteventsinone stride,aseachofthefourlegsisliftedandplacedonce. Inaddition,gaitsareclassified,dependingonmethods f0rmaintainbalance.intostaticallyanddynamicallysta

    blegaits.Themaindifferenceisthatdynamicallystable gaitsremainbalancedbymovingwhereasstaticallystable gaitsremainbalancedbyrelyingonthesupportarea formedbythelegsingroundcontact.Thegaitsdiscussed inthispaperwi11focusoffstaticallystablegaits. 3.1Forwardgait

    Staticstabilityisthefirstquestionposedtore- searcherforgaitplanning.Themainideaofstaticstabili

    tyistokeepCOG(centerofgravity)inthesupporting areaofrobotleg.Soingaitplanning,weadjustrobot bodytonextsupportingareaofthreelegsineveryending phaseofswayingleg.Inthisway,whennextswayingleg sways,theotherthreelegscansupportrobotstably.The speedofstaticwalkisslowandupto0.1m/swith0.75

    <<1,butitismoreintuifionistic.Itsmathematicde. seriptionissimpleandsoeasiertocontm1.

    Fig.3showsthesimulationgaitofrobotstaticfor. wardlocomotioninhalfcycle.Forimprovingloeomotion speed,robotbodyalsomovesatthesametimeofswaying leg.Suchstrategydecreasesthetimeforadjustingrobot bodytonextsupportingareaofthreelegssincepartof robotbodyadjustingdistancehasbeendoneinthecourse ofswayingleg.

    fb)Swayingleg3and

    bodyillOVeS

    (c)Swayingleg1andfd)BodyITIOV~Swifl~

    bodym0vtourIcsupporting

    F.3Simulationgaitofrobotstaticforwardlocomotion 3.2Turninggait

    Accordingtothedifferenceofturningradius,the turninggaitisdividedintozeroradiusturninggaitand non-zeroradiusturninggait.Becausezeroradiusturning gaitneedssmallermotionspace,itisadoptedbymostof researchers.Usuallyturninggaitplanningalsobelongsto staticstablequestion.Fig.4showsthesimulationgaitof robotzeroradiusturning.BysimulationwithAdamssoft. wal'eweknowthattheturningrangewiththreelegssup- portingislargerthantheturningrangewithfourlegssup- po~ing,sotherobotbodyturninghappenswhenoneleg liftsandadjustsitsposition.Everytimeonelegadjusts, robotturnsby30degree.

    (b)Leg3adjUStSandbody

    turnsby30de~*e

    .

.

    (c)Leg4adjusts(d)Leg2ttStS(e)Leg1a'{}ustsandbody

    tunisby30degree

    g.4Simulationgaitofrobotzeroradiusturning

    4Controlsystem

    4.1Controlhierarchy

    Two-classcontrolhierarchybasedCANbusisput

    forwardinconstructingrobotcontrolsystemandits

    structureisshowninFig.5.Localmuteplanning,motion

    ,

    lligh-lew1eomp11er

    ,..'._,

    j

    手强蜃

    i'善詹

    0

    afD0.

    CAN-HII…一.

    CAN-LILeg4

    }

    ,rrJa1nT1n',',

    rJointf,

    r-J,,.M0t0r

    Decoder

    Hall$~lsor

    ISindeleI.y1

    ?^__

    1Foot

    'j

1,Touch9ls0r

    FoweB~lsor

    L

    J

    Fig.5Controlhierarchydiagram

HIGHTECHNOL0GYI_RSIVo1.12No,4IDec.2OO6349

    modechoice,fourlegscontrollingandbodyposeadjust

    ingareaccomplishedbythehighlevelcomputer.ADSP

    TMS320LF2407basedembeddedcontrollerisdesignedto finishsinglelegcontrolincludingfourDCmotorsservo controlling.Atthesametime,thepressuresensor,dis

    tancesensorandinclinometersensorsendsignalstoone DSPfirstandthenthisDSPtransmitsthesesignalsto highlevelcomputerforprocessing.

    4.2Singlelegcontrol

    Thereareintotalsixteenpairsofservomotorand

    driversof90wattneededinquadrupedrobotiointscon

    tro1.However.atpresentmostofcontrollersarepro

    grammedinspecialcontro1algorithm.Theclosesoftware structuremakesthem1imitedinsophisticatedcontrolsys

    ten.Soweputmoreimportanceinopennessofcontroller inourresearchandalsohopetoBlakethecontrollerand driverlighterandsmaller.Sotheembeddedrobotioint servo.controlleranddriverintegrationunitisdesignedby useofDSPvIS320Ichip.Suchservomlithasfol

    lowingfeatures:

    1)FourindependentPWMsignalsoutputof16bits with20KHzfrequency.1-4motorscontrolandCANbus communication

    2)Speedtrapezoidtrackcontrolandspeedswitch smoothly.

    3)Controlalgorithmcanbecustomizedtoovercome badloadfeatures,

    Asastheencodersignalsdisposalisconcerned, DSPisprovidedwithhardwarestructurethatcaninterfacc twopairsofquadratureencoderpulsesoftwomotorsand acquirespeedandpositioninformationofmotors.111een

    coderpulsesoftheothertwomotorshavetobedisposed bysoftwareandhardwarecombination.thatis,DSPsets uptwosoftwarecountersandthenstartstwocaptureinter

    rupts(cap3andcap6)whichaleusedtocapturepulseA oftwomotorencoders.IOPC2andIOPC3areusedtoin

    terfaceBpulsesoftwomotorencoders.eneverarising edgeofchannelAisdetected.thecaptureinterruptis triggered.Intheintermptserviceroutine,thelogicallev

    elofchannelBisjudged.WhenchannelBisinlogical lowleve1.itmeansthatmotorisrunninginpositivedirec

    tion.thenthesoftwarecounteraddedup.enchannel Bislogicalhigh,itindicatesthatthemotorisrotatingin contrarydirection.Alsothesoftwarecounterminusone. Insuchaway.thesoftwarecounterupdateseve1Ttime theencoderpulsetriggers.Whenwequerythesoftware counteratf.xedintervals.thevariablevaluecanhelpus totrackthepositionofmotor,andthedifferenceofvari

    a1)leValuesattwodifferentmomentsindicatesthespeedof runningmotor.

    5Motionperformanceexperiment

    eeedfootquadrupedrobotfinishedbasicforward

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