A Robot Joint With Variable Stiffness Using

机器人,刚度,柔性

IEEETRANSACTIONSONROBOTICS,VOL.27,NO.2,APRIL2011229

ARobotJointWithVariableStiffnessUsing

LeafSprings

JunhoChoi,Member,IEEE,SeonghunHong,StudentMember,IEEE,WoosubLee,SungchulKang,Member,IEEE,

andMunsangKim,Member,IEEE

Abstract—Interactionwithhumansisinevitableforservicerobots,http://pliantcomponentisananswertothesafetyissueatthecostofperformancedegradation.Inordertoreducetheperformancedegradation,manipulatorsequippedwithvariablestiffnesshavebeenstudiedbymanyresearchers.Thispaperpresentsavariablestiffnessjoint(VSJ)designedforarobotmanipulator,http://plianceisgeneratedbyleafspringsandtwoactuatorsareusedtocontrolthepositionandstiff-nessofthejointusingfour-barlinkages.Twoactuatorsinparallelcon gurationareconnectedtothespring.Changingtheeffectivelengthofthespringresultsinachangeinstiffness.Thepositionofthejointiscontrolledviatwoactuatorsrotatingatthesamespeedinthesamedirection.AnonlinearcontrollerisusedtocontroltheVSJ,andasingularperturbationmodelisadoptedtoprovethestabilityoftheclosed-loopsystem.Experimentsareconductedtoshowthatthepositionandstiffnessarecontrolledindependentofeachother,andhavinglessstiffnessatthejointhelpsinmakinganunexpectedcollisionwithanobjectsafer.

IndexTerms—Actuators,servicerobots,variablestiffness.

I.INTRODUCTION

ERVICErobotsdesignedfordailychoresathomerequiredifferentdesignapproachesthanindustrialrobotstoen-surephysicalsafety.Fortraditionalindustrialrobots,safetyofahumanoperatorisensuredbysegregatingworkspacesofthehumanoperatorandtherobots,whereasitisdif culttosegre-gatetheworkspaceoftheservicerobotsandhumanssincethetaskrequirestherobotstosharetheworkspacewithhumans.Inordertoaddressthesafetyproblemofservicerobots,intro-ducingcompliancetothejointsoftherobotshasbeenstudied.Activecomplianceismimickingmechanicalcomplianceusingactuatorsandsensordata.In[1],arobotwithrigidjointswas

S

ManuscriptreceivedFebruary23,2010;revisedAugust24,2010;acceptedDecember13,2010.DateofpublicationJanuary20,2011;dateofcurrentver-sionApril7,2011.ThispaperwasrecommendedforpublicationbyAssociateEditorE.GuglielmelliandEditorK.Lynchuponevaluationofthereviewers’comments.ThisworkwassupportedbytheIntelligentRoboticsDevelopmentProgram,whichisoneofthe21stCenturyFrontierR&DProgramsfundedbytheMinistryofKnowledgeEconomyofKorea.

J.Choi,W.Lee,S.Kang,andM.KimarewiththeCenterforCognitiveRoboticsResearch,KoreaInstituteofScienceandTechnology,136-791Seoul,Korea(e-mail:junhochoi@kist.re.kr;robot@kist.re.kr;kasch@kist.re.kr;munsang@kist.re.kr).

S.HongiswiththeCenterforCognitiveRoboticsResearch,KoreaInstituteofScienceandTechnology,136-791Seoul,Korea,andalsowithHanyangUni-versity,133-791Seoul,Korea(e-mail:weluxmea@kist.re.kr).

Colorversionsofoneormoreofthe guresinthispaperareavailableonlineathttp://.

DigitalObjectIdenti er10.1109/TRO.2010.2100450

controlledtoexhibitcompliantmotionusingforcefeedback.De ectionsinCartesiancoordinateandorientationoftheend-effectorweredeterminedbytheforceandtorquesensordataandcompliancegain.In[2],distributedmacro–miniactuationwasusedwithdifferentactuatorcharacteristics.Alargeactuatorwasusedforhigh-torqueandlow-frequencymovement,whilelow-torqueandhigh-frequencymovementwascoveredbyasmallactuator.Inordertoreduceinertiaofthemanipulator,thelargemotorwaslocatedatthebaseofthemanipulator,andthesmallmotorwasplacedatthejoint.Formorecompactdesign,apneumaticactuatorwasusedforlowfrequencybandwidthin[3].

Whenthesensorsfailedorsamplingfrequencywaslow,activecompliancebecomesunreliabletoensuresafetyofthehumans,whichwaspointedoutbyWangetal.[4],whereacomparisonstudywasconducted.Moreover,withoutanysen-sorfailureorwithhighsamplingfrequencies,mechanicalorelectricalbandwidthofthesystemmightpreventsecuringthesafetyofhumansfromunexpectedcollisions.Sinceactivecom-plianceislimitedinensuringthemanipulatortoremainsafe,passivecompliancehasbeenpaidmuchattentionduetoitsre-liabilitywhensafetyisaprimaryconcern.Forvariousdesignsofactuatorswithpassivecompliance,see[5]andreferencestherein.

Introducingcompliance,however,posesacontrolproblem,whichhasbeenstudiedbymanyresearchers.Bicchietal.in-vestigatedarobotjointwithnonlinearspringsandthecon-trolproblemassociatedwiththemechanicalcompliancein[6].Feedbacklinearizationwasusedtocontrolajointwithcon-stantcompliancein[7]andjointswithvariablestiffnessin[8]and[9].Tomeiusedaproportional–derivative(PD)controllerandprovedthestabilityofthejointwithacompliancein[10].Spong[11]presentedtwodifferentmethodsincontrollingajointwithelasticity,whichwereusingfeedback-linearizationmethodandformingthedynamicsasasingularlyperturbedsystem.Inordertorealizeanactuatorwithpassivecompliance,ase-rieselasticactuator(SEA)wasintroducedin[12].TheSEAhadadvantagesoflow-pass- lteringshocksfromandtotheactuatorandchangingtheforce-controlproblemtotheposition-controlproblem.However,complianceduetothespringcausesposi-tioninaccuracyandlowerbandwidth.Adjustablecompliancealleviatestheseproblems.Onewaytorealizeadjustablecom-plianceistochangethepretensionofthespringconnectedtothemotor.In[13],anadditionalmomentarmandamotorwereusedtogenerateandcontrolcompliance.In[14],anonlinearspringwasrealizedwithspiralpulleysandlinearsprings.Theactuatorwasdesignedforajointofarobottohelptherobotto

1552-3098/$26.00©2011IEEE

机器人,刚度,柔性

230walk.In[15],acamdiskandrollerspressedbylinearspringswereused.Bycontrollingthepressingforcefromthespring,thestiffnesswasvaried.Inthesedesigns,onecompliantcomponentandtwomotorswererequired.Thestiffnessandpositionofthejointwerecontrolledindependentlybyeachmotor.However,itwasnotpossibleforthejointtobecomecompletelystiff.

Anotherwayistochangetheeffectivelengthofthespring.Hollanderetal.[16]usedahelicalspringandcontrolledthenumberofeffectivecoiltochangestiffness.Sincechangingthenumberofeffectivecoilchangedtheeffectivelengthofthespringaswellasthestiffness,itwasnotpossibletocontrolthestiffnessandpositionofthejointinde …… 此处隐藏：33260字，全部文档内容请下载后查看。喜欢就下载吧 ……