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Proceedingsofthe2007IEEE10thInternationalConferenceonRehabilitationRobotics,June12-15,Noordwijk,TheNetherlands InitialpatienttestingofiPAM-aroboticsystemforStroke rehabilitation A.Jackson,P.Culmer,S.Makower,M.Levesley,R.Richardson,A.Cozens,M.MonWilliams,B.Bhakta Abstract-iPAMisa dualroboticsystemcurrentlybeing developedintheUKunderaNHSNewandEmerging ApplicationsofTechnologies(NEAT)grant.Theaimofthe systemistoprovideassistiveupper-limbtherapeuticexcercise forpost-strokerehabilitation.iPAMfeaturestwoco-ordinated, pneumatically-actuatedroboticarmswhichattachtothepa- tientsforearmandupper-armtoprovideassistance,mimicking theinterventionofaphysiotherapist.Thesystemdesignand manufacturehasbeencompletedandtherobotinstalledata localhospital(StMarys,LeedsPCT,UK)insideacommunity rehabilitationunit.Thecontrolleriscurrentlydevelopedand tunedtoprovidegravitycompensationforrobots,removing anypotentiallydamagingloadsonthepatientarm.Thecontrol schemehasbeentestedinsimulationandusingamechanical armmodeltoensuresafeoperation. Twosmallscaletrialshavebeenconductedtoassesstwo facetsoftherobotdesign;firstlythemechanicaldesignofthe systemtounimpedenormalarmmovementandsecondly,its abilitytoprovidevaryinglevelsoflifttothepatientsarm toincreaserangeofmovement.Theformerofthesetrials comparesfreearmmovementinhealthyvolunteersandStroke patientswiththatwhenattachedtoiPAM.Therobotwas configuredtocompensateforitsownweight,sothehuman upper-limbwasunloaded.Itwasfoundthattherobothad nosignificantaffectonmovementpatterns.Thesecondgroup ofpatienttrialsevaluatedtheoperationofvariouslevelsof assistanceagainstgravity.Patientswereaskedtopointtoa targetwithvaryingdegreesofliftappliedtotheirupper andlowerarm.Inthosepatientswithsignificantupper-limb impairmentitwasfoundthathighervaluesofliftimproved theextentofreachbutalteredthemovementpattern.Results fromthetrialsdemonstratedthesuitabilityofcertainmodes ofoperationdependingontheseverityofpatientdisability. I.INTRODUCTION Thechallengesofhowtoprovidefrequentandeffective therapeuticrehabilitationtothoseaffectedbystrokeisa universalissueandonewhichwillonlyamplifyastheeffects ofanagingpopulationarefelt.Atpresentaround300,000 peoplesuffertheaffectsofstrokeintheUKalone,with 85%ofthoseexperiencingadegreeofarmparesisfromthe onset1.After5years,oneinfourstillreportdifficulty usingtheirpareticarm2.Rehabilitationprogrammesaim ThisworkwassupportedbyNEATGrantE027 A.Jackson,P.Culmer,M.LevesleyiswithDepartmentofMechanicalEn- gineering,UniversityofLeeds,UKA.E.Jacksonleeds.ac.uk S.MakoweriswithLeedsPrimaryCareNHSTrust,UK R.RichardsoniswithDepartmentofComputerScience,Universityof Manchester,UK A.CozensiswithDepartmentofRehabilitationMedicine,Grampian NHS,UK MMonWilliamsiswithDepartmentofPsychology,Universityof Aberdeen,UK B.BhaktaiswithFacultyofMedicineandHealth,Univer- sityofLeeds,UKandLeedsTeachingHospitalsNHSTrust,UK B.Bhaktaleeds.ac.uk toincreasepatientsindependencebyfocusingoneveryday tasksofselfcare,domesticdutiesandrecreation.Through thepracticeoftheseactivities,there-learningofmotorskills canleadtoagreatlyincreasedcapability.Thisplacesa significantburdenontheNationalHealthService(NHS), withseverelylimitedphysiotherapyresources,patientsdo notspendenoughtimeengagedinrehabilitationactivities. Augmentingtraditionalphyicaltherapywithrobotassisted therapyisonepotentialsolutionthatisbeinginvestigatedat severalinstitutionsworldwide. Oneparticularapproachutilisedisthesinglepointof attachmentsystemasseenontheMIT-Manus3,Gentle/s 4andUECM5robots.Thesesystemsrelyonasingle attachmentpointatthewrist,sometimesinconjunctionwith apassiveslingmechanismattheupperarmtosupportthe shoulderandoffsetsomeofthearmmass.Arecentstudy 6withtheInMotion2system(acommercialmodelofthe MIT-Manus)demonstratedsmallbutpositiveimprovements inmotorimpairmentscoresfor27moderateandchronic strokepatients.TheGentle/srobotsystem,whichisbased aroundamodifiedHapticMaster,hasbeenutilisedina singlecasestudy,comparingimprovementafteraperiod ofrobotinterventioncomparedtonointerventionandsling suspensionintervention.Theinvestigationdemonstratedthe superiorityofrobotinterventioninbothcases7.TheUpper ExtremityCompoundMovements(UECM)rehabilitation robotdevelopedatTsinghuaUniversityinChinahasa2 DoFplanarconfiguration.Itcanoperateinbothassistiveand resistivemodesdependingonpatientability.Aclinicaltrial hasbeenundertakenwith23chronicstrokepatients.Results showthemajorityofpatientsexperiencedanimprovement inmotorfunction8.Theresultsfromallthesetrials demonstratetheefficacyof robotassistedphysiotherapy. Intheabovesystems,thearmiscontrolledintermsof theendhandtrajectory,asopposedtohumanlimbco- ordination.Alimitationofsuchsystemsistheinabilityto fullyconstraintheupper-limb.Asingleendeffectorposition doesnotdefinespecificelboworshoulderrotations,hence jointco-ordinationisnotviable.Inaddition,assistiveforces atthewristinpatientswithelbowspasticityandlowtoneor subluxationattheshoulder,mayleadtoinappropriatelevels oftorqueattheshoulderjointcausingpainordiscomfort. ConventionalphysiotherapyinvolvesthePTactingattwo contactpointsonthearm;oneonthelowerarm,close tothewristandthesecondaroundthemid-pointbetween elbowandshoulder.ThisallowsthePTtofullyconstrain theorientationandpositionofthelimbandco-ordinatethe armsegmentsinatherapeuticallymeaningfulmanner. 1-4244-1320-6/07/$25.00(c)2007IEEE250 Proceedingsofthe2007IEEE10thInternationalConferenceonRehabilitationRobotics,June12-15,Noordwijk,TheNetherlands Fig.1.TheiPAMsystem Onesolutiontotheseproblemshasbeenaddressedby thedevelopmentofexo-skeletontyperobotsystemsthatare fittedalongoraroundthelimbtoallowagreaterdegree ofco-ordination.ThePneu-WREX9,RUPERT10and ARMin11robotsystemsalladoptthisapproach.Pneu- WREXisa5DoFrobotsystemmadeupfromapairof 4barlinkages.Itisactuatedbypneumaticactuatorswhile gravitycompensationisprovidedbyinterchangeablesprings. RUPERT(RoboticUPperExtremityRepetitiveTherapyde- vice)has4activeDoF,althoughwithonlyonedegreeat theshoulder,movementsarerestrictedtoplanermovement withelbowextension,forearmpronationandwristflexion. Aseconditerationisunderdevelopment12.TheARMin systemisapartialexo-skeletonsystemwith4activeDoFand 2passive.Actuationisprovidedbycablesdrivenbyelectric motorsimplementedthroughimpedancecontrol.Trialswith theARMinsystemdemonstratedadecreaseinthelevelof robotassistanceduringmovementsasthetrialprogressed, indicatingsomemotorimprovement13 II.iPAMDUALROBOTSYSTEM TheintelligentPneumaticArmMovement(iPAM)robotic systemisadualrobotsystem(Fig.1)forprovidingassistive therapeuticexerciseforpatientssufferingfromupper-limb paresisasaresultofStroke.Eachoftheroboticarmshas 3activeDoFandassiststhepatientviaaspeciallydesigned orthosis.Theorthoses,attachedviaapressure-cuff,are locatednearthewristonthelowerarmandmidwaybetween elbowandshoulderontheupperarm.Theorientationofeach orthosisisunconstrained,witheachofthe3rotationalaxes passingthroughthearmscentre.Thisallowstheorthoses toalignwiththearm,regardlessofendeffectororientation. Actuationofeachrobotisprovidedby3pneumaticlow- frictioncylinderswhicharecontrolledusing6proportional controlvalves.Positionandforcesensorsareusedtomonitor Fig.2.ThesixDoFofthehumanarmcontrolledbyiPAM positionofthehumanarmandforcesappliedtothepatient armbytherobotsystem.Thecombinationofthe3powered DoFattheendofeachrobotarmallowscontrolof6DoFsof thehumanarmattached.Thedegreesoffreedomofthehu- manarmareshowninFig.2.Thisconfigurationisanalogous totheapproachusedbyphysiotherapists(PT)whenholding thepatientslimbsegmentsduringconventionalupper-limb rehabilitation.Usingthekinematicmodelsoftherobotand humanarmswithmeasurementsfromtheanglesensors,it ispossibletomonitorthepositionoftheendorthosesand thepositionofthepatientarm.Theresultant6DoFcontrol givesthepotentialforacontrolstrategythatfacilitates coordinatedmovementofthearmasawhole,ratherthanjust themovementofthedistalsegment(e.g.forearmorhand). ThisisakeyaspectoftheiPAMsystem.Additionally,active controloftheupperarmrobotalsoallowsforfullsupport oftheshouldercomplexduringmovement. III.CONTROLSYSTEM Withtwophysicallyindependentrobotsattachedtothe patientarm,effectiveco-ordinationbetweeneachrobotis paramount.Mis-alignmentoftherobotend-effectorscould placeundesirabletorquesontothepatientslimb.Itisthere- forenecessaryfortheimplementedcontrolschemetobe co-operative.Thisrequiresamappingfromeachrobots taskspaceintoacoordinatesystemrepresentingthehuman arm.Thishasbeenachievedusingakinematicmodelof thehumanarm14asshowninFig.3.Utilisingthe kinematicmodelofthearm,andthesystemmeasurements, itispossibletodetermineboththepositionsandtorques exertedonthelimb.Iftrajectoriesaretobedefinedinhuman jointspace,thenextlogicalstepistoprovideassistancein thesameco-ordinatesystem.Anadmittancecontrolscheme hasbeendevelopedthatmodulatestheinputtrajectoryfor eachDoFasafunctionofmeasuredforce/torqueandtakes theform: F Kx+sCx whereKandCarestiffnessanddampingtermsrespectively. Thisallowsthecharactisticsofassistancetobealteredin eachDoFofthehumanarmindepentently.Formoredetails ontheadmittancecontrolschemesee15. InitiallyforiPAM,threespecificcontrolschemesareto beimplemented: Gravitycompensationmode:Robotremainsingravity compensationmode,i.e.therobotactuatessufficiently, 1-4244-1320-6/07/$25.00(c)2007IEEE251 Proceedingsofthe2007IEEE10thInternationalConferenceonRehabilitationRobotics,June12-15,Noordwijk,TheNetherlands Shoulder internal/externalrot. ;05 Shoulder abduction/adduction I Harnessrestraint Shoulder girdle elevation Shouldergirdle protraction Elbowextension/ flexion Fig.3.6DoFkinematicarmmodel dependingontheorientationoftherobotjoints,to lifttheweightoftherobotitselfandtheorthoses.As suchtherobotfeelsweightless,butpatientisfreeto movetheirarmtomeetthedesiredtargets.Noassisted movementisprovidedbytherobot Handtrajectorymode:Actslikeasinglepointofattach- mentrobot.Upperrobotoperatesingravitycompensa- tionmodewhilethelowerrobotoperatesaCartesian admittancecontrolscheme .Jointcontrolmode:Robotarmsprovideadmittance controlasoutlinedaboveaboutthehumanjointsto providecoordinatedmovement Fortheinitialtrials,onlythefirstofthesecontrolschemes isutilised.AnextensionofthiscontrolschemeallowsiPAM tooffsetsomeoftheweightofthepatientsarmtoo.This providesaneffectsimilartoaslingsuspensiondevice. IV.PRELIMINARYTRIALS Preliminarytrialswereconductedaspartofaparallel processtocollectqualitativedataonuserandtherapist perceptionoftheiPAMsystemandtheproceduresasso- ciatedwithit.Thetrialsconsistedoftwodistinctsetsof experimentswhichformedtheuserinvolvementcomponent oftheuserperceptionstudy. A.Aims Thefirstexperimentwasasmallscaleinvestigationto determinewhetheraparticipantsmovementsarecomfortable andunimpededbytherobotsysteminitspassivemode. Thisisofgreatimportancebecausethedesignofthe systemdependsuponnotexertingforcesortorquesonthe upper-limbunlessexplicitlydesiredbythecontrolscheme. Thesecondexperimentisaimedtomeasuretheeffectson Endmarker Pointermarker Startmarker Fig.4.Theconfigurationofexperiment1 movementswhenvaryingdegreesofrobotassistanceare appliedtocounteracttheeffectsofgravityontheupperarm andforearm.Inadditiontotheaimsabove,bothexperiments serveasausefulplatformfordatacollectionthatcanbeused tofurtherdevelopthevariouscontrolmodesoftherobot. B.Method 1)Experiment1:Astandardisedmovementtaskwas constructedthatcouldbeperformedbothwithandwithout therobot.Thestartandend-pointsofthemovementwere definedbytwomarkers;thefirstwaslocatedinacomfortable positionbytheparticipantswaist,thesecondwasoffset distally,mediallyandsuperiorlyfromthefirstmarker.Afull movementcyclewasperformedbyfirstlytouchingthestart markerwithapointingimplementprovidedtotheparticipant, movingtotouchtheendmarkerandthenreturningtothe startmarker,asillustratedinFig.4.Participantswereasked toperformthemovementcycle15(fifteen)timesundertwo conditions;withoutiPAMattachedandwithiPAMattached. Thiswasdividedinto3(three)equalsetstoavoidfatigue influencingtheresults.Themovementwasdesignedtobe bothrealisticandtoinvolveallofthesystemsDoFsuch thatitrepresentsageneralcase.TheiPAMseatingsystem wasusedforbothtestconditions.Inadditiontoproviding aconsistentseatingheightitallowedtheuseofaharness restrainttominimisemovementofthetrunk.Thishelpsto maintainrepeatabilitybetweentests.Forthetestsinvolving iPAManoperatingprotocolwasdevisedtoensureboth correctoperationofthesystemandtestrepeatability.The protocolissummarisedbelow: 1)PlaceiPAMin“gravitycompensation“mode 2)Seatparticipantandfitharnessrestraint 3)Re-lineupper-armorthosisandattach 4)Re-lineforearmorthosisandattach 5)Measurepositionoforthosesonupper-limbsegments Underbothtestconditionsmovementwasrecordedusing amotionanalysissystemwithactiveinfra-redmarkers.The NDIOptotrakCertushashighaccuracy(upto0.1mm)and 1-4244-1320-6/07/$25.00(c)2007IEEE Shoulder4 extension/flexion KEY( Orthosisattachmentpoint - DoF(inpositivedirection) AShoulderorigin 06 252 Proceedingsofthe2007IEEE10thInternationalConferenceonRehabilitationRobotics,June12-15,Noordwijk,TheNetherlands TABLEI SUMMARYINFORMATIONFORTHESUBJECTSINVOLVEDINTHEIPAM PRELIMINARYTRIAL SexAgeSinceStroke(Years)-Type POMale28N/AN/A PIFemale552|LeftCVA P2Male611LeftCVA P3Male381LeftCVA P4Female531LeftCVA P5Male463LeftCVA P6Male831LeftCVA TABLEII THEVERTICALFORCEPROVIDEDBYIPAMINEACHOFTHETEST CONDITIONS UpperarmForearm NoLiftONON LowLift3N4N MediumLift6N8N HighLift9N12N isapprovedforuseinmedicalenvironments.Itwasusedto recordthepositionofbothmarkersandthepointerrelative toapredefinedcartesiancoordinateframe.Inaddition,when iPAMwasconnectedtotheparticipantitwasusedtocollect arangeofdataonorthosisandupper-limbposition. Atotalof3(three)subjectswererecruitedforthefirst experiment.APTexaminedeachofthesubjectsprior totestingtodeterminesuitabilityandassessimpairment. Thesubjectswerecomprisedof1(one)healthysubject (PU)and2(two)patientswithstroke(P1,P2)whohave righthemiparesisaffectingvoluntaryreachingmovement.A summaryofallthepatientsrecruitedforthetrialsisgiven inTableI. 2)Experiment2:AmodifiedversionofExperiment1 wasdesignedtotesttheaffectofaddingvaryinglevelsof lifttotheupper-limb.Anewmovementwasdefinedusing onlyasingleendmarkerwhichwaslocateddistally,just exceedingthemaximumhealthyreachoftheparticipant.The startpointofthemovementwasdefinedtobeacomfortable restpositionwiththeupper-limbflexed90degreesatthe elbow.Thechangeinmovementdefinitionwasimplemented toallowmeasurementofboththepatternandrangeofupper- limbmovement.Thefullmovementcyclebeginsatthestart position,movingtotheendmarkerandthenreturningtothe startposition. Theexperimenttested4(four)differentconditions;no, low,mediumandhighassistanceagainstgravity.Noassis- tancecorrespondstothestandardgravitycompensationmode ofiPAMinwhichtheactuatorscompensatefortheweight oftherobot.Theamountofliftagainstgravitythateach conditionprovidesisdetailedinTableII. ThesameoperatingprotocolasdescribedforExperiment 1wasusedtoensureaconsistentconfiguration.Afterthis initialsetupthelevelofliftwasgraduallyintroducedbythe controlschemeoveraperiodof5secondstopreventsudden P2iPAM P2FreeL P1iPAM P1FreeF- POiPAM POFree - H- : -I- -1d -Hd 405060708090100 Peakdeviation(mm) Fig.6.Boxplots forthepeakdeviation movement.Duringtheintroductionoftheliftforce,oratany timeduringtheexperiment,theparticipantwasinstructedto reportanydiscomfortatwhichpointtheliftforcewould besafelyremovedandtherobotsystemdetachedfrom theupper-limb.Participantswereaskedtobeginmovement shortlyafterthelifthadbeenintroduced.Foreachcondition 15(fifteen)repetitionswererecorded,againdividedinto3 (three)equalsets.MovementwasrecordedusingtheNDI OptotrakCertusmotiontrackingsystemandtheiPAMrobot systemasdescribedforExperiment1. Afurther4(four)subjectswererecruitedforthesecond experiment.Allofthesubjectshadsufferedfromstroke (P3,P4,P5,P6),assummarisedinTableI.Ofthefoursub- jects,1(one)wasrejected(P6)becausetheyhadnofunc- tionaluseoftheaffectedupper-limb,thereforetoinitiateand maintainanymovementrequiredactiveinterventionfroma PT.Thislevelofimpairmentwillbemoresuitedtofuture workwiththecooperativeassistivecontroller controller14. C.Results 1)Experiment1:Allsubjects(PO,P1,P2)completedthe activitiesinExperiment1successfully,withnoreportsof discomfortordiscontentment.Fig.5(a)showstheresultant trajectoriesfollowedbyeachofthesubjects.Frominspection oftheseresults,itisevidentthatthegeneraltrendof movementissimilarbetweenthefreeandrobotattached movements,withnomarkeddifferenceintherange,or pattern,ofmovement.Analysisoftheresultsshownin Fig.5wasperformedtoquantifyanydifferencesbetween theexperimentconditions.Thepeakdeviationfromahy- potheticalidealstraight-linetrajectorywascalculatedfor eachmovementattemptandusedasameasureofmovement efficiency.Fig.6showsthedistributionofresultsbetween thetworeachconditionsforeachsubject.Theresultsshown inFig.5andFig.6indicatethat,wheninapassivegravity compensationmode,theiPAMsystemdoesnotimpede upper-limbmovement.Thissuggeststhatfirstly,thegravity compensationmodeiseffectiveandtherearenoerroneous 1-4244-1320-6/07/$25.00(c)2007IEEE d 253 Proceedingsofthe2007IEEE10thInternationalConferenceonRehabilitationRobotics,June12-15,Noordwijk,TheNetherlands 0.5 0 -0.5 0.9 *0.70 ML(m)-0.5AP(m) (a)PO 0.50.9 0.7 ML(m) /-0.2 -0.4AP(m) (b)P1 Ideal 0.4Free-reach iPAMattachedreach E 0.2 0 0.90.2 ML()-0.2AP(in) (c)P2 Fig.5.FreemovementvsiPAMattachedmovement forcesappliedtotheupper-limb,andsecondlythatthe combinedrobot-humansystemdoesnotimposekinematic constraintsontheupper-limb. 2)Experiment2:Allofthesubjects(P3,P4,P5)selected forExperiment2completedthemovementssuccessfully. Therewerenoreportsofdiscomfortforanyofthedifferent liftlevels.Fig.7showsrepresentativeplotsofthetrajectory followedbyeachsubject,summarystatisticsforthefull rangeofmovementsarepresentedinTableIII. FromFig.7,itisapparentthatthesubjectshaddiffering responsestothelevelsofliftprovidedbyiPAM.SubjectP3 showsnodiscernibledifferenceintherangeofmovement, withsimilarmovementpatternsacrossallofthelevelsof lift.Conversely,subjectsP4andP5showanincreasein thedistalextentoftheirreachasthelevelofliftisraised. The