外文翻译--仿生物脊柱的人形机器人Robota的设计 英文版.pdf

IEEE/RAS-EMBSInternationalConferenceonBiomedicalRoboticsandBiomechatronicsPisa,Italy,February20-22,2006DesignofaBiomimeticSpinefortheHumanoidRobotRobotaLorenzoRoos,FlorentGuenter,AndreGuignardandAudeG.BillardAutonomousSystemsLaboratory3SchoolofEngineeringEPFL-EcolePolyt´echniqueF´ed´eraledeLausanneStation9CH-1015Lausannefflorent.guenter,aude.billardgepfl.chAbstractThispaperpresentsaprototypeof3degrees-of-freedomarticulatedspineforthedoll-shapedhumanoidrobotRobota.Thisworkfollowsanapproachthatemphasizestheneedforahighhuman-likelinessinboththeexternalfeaturesoftherobotandinthekinematicsofitsmotionstoenhancehuman-robotinteractions.Thedesignofaspinalcordforourhumanoidrobotsatisfiesbothcriteriainprovidingofferingasmoothhuman-likeparallelmeansofbendingforwardandsideways.IndexTermsBio-mimeticSpine,HumanoidTorsoI.INTRODUCTIONTheRobotaprojectdesignsaseriesofbiomimetichu-manoidrobots12.Since1998,Robotahasbeingusedaspartofstudieswithautisticchildren3,4.Thesestudiescomparetheeffectthathuman-likefeaturesmayhaveontheinterestthatchildrenwithautismshowininteractingwithanotheragent.Thus,expressinghuman-likecharacteristics,bothintherobotsbodyfeaturesandintherobotsbehaviors,hasbeenforlongakeyconstraintinthedesignofRobota.ThecurrentprototypeofRobota,whichwedescribehere(seeFigure1),willfindanapplicationinavarietyofworkonhuman-robotinteractions,conductedatourlaboratory,see,e.g.5,6.Inthese,westudythemeansbywhichonemayendowtherobotwithhuman-likemotionsthroughimitationlearning.Ahighresemblancebetweenthehumanbodyandthatofrobotsimplifieslargelythesocalled“correspondenceproblem”7,inwhichthemotionofthehumanmustbelettocorrespondtothatoftherobot.Sofar,ourworkhasconcentratedonteachingtherobotsimplemanipulatorymotionsinvolvingthetwoarms.ThedesignofaflexiblespinefortheRobotarobotwillallowustoextendthisworktoteachingmotionsinvolvingthewholetorso.Byrequiringthatthespineflexesthesamewayasthatofthehumanbodyalongthepanandtiltdirectionsofmotion,weensureagoodcorrespondencebetweenthehumanmotionsandthatoftherobotduringkinestheticThisworkissupportedinpartbytheSwissNationalScienceFoun-dation,throughgrantno620-066127oftheSNFProfessorshipsprogramandbytheEuropeanCommissionDivisionISTFutureandEmergingTechnologies,IntegratedProjectROBOT-CUB.teaching(suchasthatdoneonourFujitsuHOAP-2robot,seeFigure2).In8,wepresentedaprototypeofa7degreesoffreedomarm(DOF)andofa3DOFspairofeyesforanextendedversionofRobota.Inthispaper,wepresenttherecentdevelopmentofanarticulatedspinetoendowtherobotwithhuman-likemotionsofitstorso.Wereportonthevariousstagesofdesign,takingthetimetode-scribesolutionsthat,althoughfeasibleintheory,appearedunpracticalwhenimplemented.Althoughthisisunusual,theliteraturetendingtoreportusuallyonfinalworkingprototypesonly,webelievethat,insomecases,itisalsoinstructivetoreportonunfeasiblesolutions,especiallywhenthosecanbeprovedwrongonlywhencreated.II.STATEOFTHEARTThedesignofhumanoidrobotsformagrowingbodyofroboticsresearch.However,thevastmajorityofthoseworksfollowarelativelyclassicalapproachinthedesignoftheactuatorsoftherobotstorso,bylocatingthoseseriallyatthelevelofthewaist.ExamplesofsuchrobotsincludeHondaASIMO9,SonyQ-RIO10,FujitsuHOAP-1&-2andHRP-2P11developedbytheKawadaIndustries.AllofthesehaveeitheroneortwoDOFs,whereasthehumanoidrobotWABIAN12fromWasedauniversity,COG13atMITandARMAR14,ahumanoidrobotdevelopedattheKarlsruheuniversityhavethreeDOFs.Thereexists,however,afewsolutionsthatfollowmoreofabiomimeticdesign.Forinstance,theCLAandKENTA15,16robots,developedatTokyoUniversity,offertwosolutionsofarticulatedspine,thatmimicsthehumanspine.Forrecall,thehumanspineconsistsof24vertebraethatarestackedontopofeachother.Betweeneachvertebraisasoft,gel-likecushioncalledadiskwhichplaytheroleofshock-absorberandkeepsthebonesfromrubbingagainsteachother.Eachvertebraisheldtotheothersbygroupsofligaments.Thespinalcolumnalsohasjointscalledfacetjoints.Thefacetjointslinkthevertebraetogetherandgivethemtheflexibilitytomoveagainsteachother.Theaveragerangeofmotionare§30fortheflexion-extension,§40foradduction-abductionand§30fortherotation.Fig.1.CurrentprototypeofthenewRobota.Itencompassa6DOFsarmwith1DOFgripper,3DOFspairofeyesmountedwith2cameras,3DOFsneckand3DOFsspinalcord.Inalatterstage,theprototypewillbeembeddedinaplasticcoatingsimilartothatofcommercialdoll,seeFigure3,toensurethatallmechanicalpartsarehidden.ThespineoftherobotKENTAisconstitutedof10jointswith3DOFsperjoint,soastomimictheassemblyofvertebraeinthehumanspine.40actuatorsareusedtocontrolthespine(See15).IntherobotCLA,thespineconsistsoffiveflexiblejoints,separatedbyarubberlayer.Therubbersendowthespinewithanaturalflexibilityandarepreconstraintinaway,suchthattheequilibriumpointliesinaverticalstraightposition.8cableswithactuatorsplaytheroleoftendonsbetweentheclavicleandpelvistomovetheentirespine(See15).Whilethesespinesareinmanywaysthebestexampleofsuchdesign,theyrequiretoomanyactuatorsandwouldnotfitthesmallbodyoftheRobotarobot.Thereexistalsootherhyperredundantrobots,albeitnothumanoids,suchastheroboticelephantstrunkoftheClemsonUniversity17orvarioussnakelikerobots(forexample18,19),whichofferinterestingsolutions.TheelephantstrunkoftheClemsonUniversityiscomposedofdiskslinkedtooneanotherby2-DOFjoints.Thesedisksareusedtodrivethecablesystemwhichactuatesthetrunk.Betweentwodisks,therearefourpreconstraintspringstocreateanequilibriumpointwhenthentrunkisinastraightposition.Thesnakelikerobotscitedabovearedrivenbypneumaticpumps.TheSlimeRobot18isconstitutedofdisksactuatedbythreepneumaticactuatorbetweeneachofthem.TheOmniTreadrobot19iscomposedofdifferentsegments,eachofthemactionedbycaterpillars.Betweentwosegments,thereisapneumatic2DOFsjoint.Theserobotsofferinterestingsolution,especiallyintheiractuationsystem.However,theserobotshaveastructurewhichismeanttosupportalowloadhorizontally,and,thus,isnotoptimizedtoworkunderhighcompression,Fig.2.AdemonstratoristeachingamovementwhichrequiresbendingofthetorsotothehumanoidrobotHOAP-2asitisthecaseforthespineofatwolegsstanding-uphumanoidrobot.III.MECHANICALDESIGNTheRobotaprojectisconcernedwiththedesignandconstructionofaseriesofmultipledegreesoffreedom(DOF)doll-shapedhumanoidrobots,whosephysicalfea-turesresemblethoseofahumanbaby.TheRobotaprojectispartofacurrenttrendofroboticsresearchthatempha-sizestheneedfortherobottobearsomehumanlikenessbothinitsbodyfeaturesandinthekinematicsofitsmotionstoenhancehuman-robotinteractions,see,e.g.20,21,22,23.Asmentionedintheintroduction,theuseoftherobotRobotaaspartofstudieswithchildrenwithautism3setsanumberofconstraintsonitsdesign,includingthatitssizeremainsmall,itsweightlight,itscostlowandthatitsfeaturesremainaestheticandfamiliar(similartothatofothertoysthechildrenwouldencounterintheirdailylife).InordertoensuretheoverallaestheticoftherobotRobota,wetookasreferencetheaveragesizeofa60cmtallcommercialdoll,seeFigure3andamaximalweightof4kg.TheseconstraintswereusedforallprecedentprototypesdesignedforRobota:The7DOFsarm,the3DOFseyesandthe3DOFsneck8,24.Giventheexistingprototypes,thefollowingconstraintsweregivenforthedesignofthespine:1)Thespinemustbestrongenoughtosupportaloadof2Kglocatedat80mmupthelastvertebrae(seeFig.12).2)Thespinemustsmallenoughtofitinacylinderof210mmhighanddiameterof120mm.3)Theweightmustnotexceed1.2kg.4)Theactuationmustbedonebyamaximumofthreemotors,toremaincheapandeasilycontrollablebyanon-boardcontroller(aPocketPC).5)Thespinemustbeabletobendwithanangleof40ineachdirection.Whilethereexistsafewprototypesofspinesforhu-manoidrobots,see15,16andtheintroductionforareview,noneofthesesuitedtheconstraintslistedabove.ThespineoftheKENTArobotistoobigandhastoomanyactuators.ThesolutionusedforCLAismorerelevantFig.3.DollusedasreferenceforsettingthesizeofthenewrobotRobota.toourproblem.However,itstillhastoomanyactuatorsforourpurposeanditwouldnotbesuitabletocarrytheload(2Kg)oftherobotsheadandwouldleadtobucklingproblems.Ensuringthatallcomponentsremainsmall(tofitwithinthedollsbody)whilesupportinganimportantload(inproportiontotheoverallsizeofeachlimb)isandhasalwaysbeenatremendouschallengeinalltherealizationswehavedeveloped.A.ThefirstdesignTokeepthecontroloftherobotsimple,wedecidedtodecouplethethreeDOFsofthespine.TwoDOFsareusedtobendthespinefromfronttobackandfromlefttorightrespectively,seeFigure11.ThethirdDOFofthetorso,supportedbythespine,drivesthehorizontalrotationoftheshoulders.AclassicalsolutionisusedfortherotationofthethirdDOF.ThepointwastofindafeasiblesolutionforthetwofirstDOFs.Differentsolutionshavebeenexploredduringtheprojectusingdifferenttypesoftransmissionmeansforthemovement.1)Cablesystem:Thefirstdesignofthespineconsistedinastackofvertebraeseparatedbyrigidpolymerrings.Theringsintroducedaspacebetweenthevertebraeandlimitedthelateraldisplacements(seeFig4).Thevertebraewerefixedonetoanotherbyaspringpassingthroughtherings.Theshapeoftheringsallowedbendingbymaximum30betweentwovertebrae.Therewasaflatpartbetweentheringsandthevertebraetoallowabetterstabilityintherestposition(straightvertical).Holeweredrilledateachextremityofthecrossformedbythevertebraetofitthevariouscablesneededfortheelectronic.Thefirstproblemweencounteredwiththisdesignwasthatthelengthofthespinewouldchangewhenitbended,becausethecablesonbothsideswouldnotchangebythesamelength(whenthetwocablesarefixedalongoneaxis,onewindsupwhentheotherwindsout).Thesecondproblemwasthat,ifwefixedthecablesonlytotheuppervertebrae,thespinewouldbendeachvertebraeseparatelyandoneaftertheotherone,startingwiththefirstone.Thus,Fig.4.ArubberdiskisplacedbetweeneachvertebraeandaspringisusedtofixonevertebraetoanotherFig.5.Thelinkbetweentwovertebraeisacardanjointandcompressionspringsareplacedoneachbranchtoinsurethestabilitythemovementwouldnothavebeensmoothlydistributedalongthespine.2)CardanJoint:Toaddressthefirstproblemmentionedaboveandinspiredbytheelephantstrunksolution17,wereplacedthepolymerringswithacardanjointwithcompressionspringsplacedoneachbranchofthecrossshapevertebraenearthecables(seeFig5).Thecardanjointsolvestheproblemofthedifferenceofdisplacementbetweenantagonistcables.However,thisstillleaveduswithacontrolproblem,whenthecablesarefixedonlytotheuppervertebrae.Here,theproblemisnotthatthevertebraewillmoveoneaftertheother(eachjointactasdirectingaxisandthespringsdistributetheforcesacrossallvertebrae).Whenattachingabigloadtothespine(hereabout2kg),therewillbesomebucklingproblems,ifthespringsarenotstrongenough.3)Screwsinsteadofcables:Tosolvethebucklingproblemoftheprecedentsolution,inathirddesign,thecableswerereplacedbyscrewsandcardanjoints(seeFig6).Ateachlevel,wenowfindfourscrewsinsteadofcables.Thescrewshavedifferentstepdependingonthelevel(smallstepatlowerlevelandincreasingforhigherlevel).Thiscreatesadifferenceofdisplacementbetweentwoconsecutivevertebrae.Thedifferentscrewsarelinkedwithcardanjoints.Withthissystem,thedisplacementofeachvertebraisundercontrol.Thedrawback,still,isthattoachievethedesiredbendingofthespine,thestepofthescrewlocatedatthelastlayerbecomesverybigand,thus,requiresalargerintervalbetweentwovertebrae.Thus,thefinalprototypewouldendupbeinglargerthanoriginallyplanned.4)Hydraulicsystems:Afterthecablesandscrewtrans-mission,wehavedecidedtoexplorehydraulicsolutions.ThefirstdesignispresentedinFig7.Eachvertebraeislinkedtothenextoneusingasphericalbearing.Thistimeagain,eachvertebraeconsistsofacrossshape.EachFig.6.ThelinkbetweentwovertebraeisacardanjointandcompressionspringsareplacedoneachbranchtoinsurethestabilityFig.7.Thelinkbetweentwovertebraeisacardanjointandcompressionspringsareplacedoneachbranchtoinsurethestabilitybranchacrosstwovertebraeislinkedthroughatwistedtube.Betweentwotubes,thevertebraeisdrilledtoleaveawayfortheliquid.Thuseachstackoftubesformaextensiblecolumn.Ahydraulicpumphasbeendesignedspecificallyforourpurpose.Thepumpislocatedatthebaseofthespine.Twomotorstransmitthemovement,viaasetofreductiongears,totwoparallelendlessscrewsthatmovestwopistonsinsidetubes(seeFig8).Thiscreatesapump-in/pump-outtractionsystem,similartousingapairofsyringes,(seeFig.9).Prototypesoftwistedtubehavebeenproducedtotesttheresistanceofsuchasystem.Theprototypesweretestedunderapressureof3bar(theminimalpressurerequiredtomovealoadof2kgSeeIII).Noneofthetubeswehavetestedweresufficientlyresistanttosuchpressure.Thesensitivepointsarethefoldoftheaccordionshapedtubes.Theseproblemshavedrivenustoamoreclassicalsolutionbyusingpistonsinsteadofcompressibletubes.Thepistonsaremuchmoreresistanttohighpressure,buttheproblemisthedifferenceoffrictionbetweentheFig.8.Cutviewofthetractionsystem.Fig.9.Workingprincipleofthehydraulicactuationofthespine.Fig.10.Dimensionsofthetorso.differentpistons.Weareunabletoguaranteethatallpistonswillhavethesamecomportment.ThatcanresultinthespinalcordforminganSshape.Topreventthisproblem,wehaveplacedfourspringsbetweeneachvertebrae.B.Prototypeofa3DOFsspinalcordThecurrentprototypeofspineisabout200mmhighforadiameterof90mm.Itsweightisabout1Kganditcansupportaloadof2Kglocatedat80mmonthespine(seeFig.12).Thehydraulicpumpinlocatedatitsbase(seedescriptioninIII-A.4),and,thus,isnotpartofthesupportingload.Thecompletespineiscomposedoffourvertebrae,linkedthroughsphericalbearing.AteachlevelFig.11.Maximumbendingofthespine