UseofVoiceRecognitionforControlofaRoboticWeldingWorkcellABSTRACT:Thispaperdescribesworkunderwaytoevaluatetheeffectivenessofvoicerecognitionsystemsasanelementinthecontrolofaroboticweldingworkcell.Factorsbeingconsideredforcontrolincludeprogrameditoraccesssecurity,Preoperationchecklistrequirements,weldingprocessvariablecontrol,androbotmanipulatormotionoverrides.Inthelattertwocategories,manualvocalcontrolisbeingcomparedagainstmanualtactilecontrolandfullyautomaticcontrolintermsofspeedofresponse,accuracy,stability,reliability.Andsafety.IntroductionVoicerecognitiontechnologyisnowrecognizedasapotentialmeansforeasingtheworkloadofoperatorsofcomplexsystems.Numerousapplicationshavealreadybeenimplemented,areinvariousstagesofdevelopment,orareunderconsideration.Theseincludedataentry,controlofaircraftsystems,andvoiceidentificationandverificationforsecuritypurposes.Voicecontrolhasalsobeenproposedforuseaboardthespacestation.Oneprimeareaforapplicationwouldbecontrolofsomefunctionsofrobotsusedforintraandextravehicularinspection,assembly,repair,satelliteretrieval,andsatellitemaintenancewhenacrewmemberisservinginasupervisorycapacityorthesystemisoperatinginateleoperationmode.Voicecontrolofsensorsandprocessvariableswouldfreethecrewmembershandsforothertasks,suchasdirectcontroloroverrideofthemanipulatormotion.Similarly,theworkloadassociatedwithcontrolofmanyonboardexperimentscouldbeeasedthroughtheuseofthistechnology.Thispaperdescribestheapplicationofvoicerecognitionforcontrolofaroboticweldingworkcell.Thisisacomplexsysteminvolvinginputsfrommultiplesensorsandcontrolofawidevarietyofrobotmanipulatormotionsandprocessvariables.Whilemanyfunctionsareautomated,ahumanoperatorservesinasupervisorycapacity,readytooverridefunctionswhennecessary.Inthepresentinvestigation,acommerciallyavailablevoicerecognitionsystemisbeingintegratedwitharoboticweldingworkcellatNASAMarshallSpaceFlightCenter,whichisusedasatestbedforevaluationanddevelopmentofadvancedtechnologiesforuseinfabricationoftheSpaceShuttleMainEngine.Inthesystemunderdevelopment,somefunctionsdonotyethaveautomaticclosedloopcontrol,thusrequiringcontinuousmonitoringandreal-timeadjustmentbythehumanoperator.Presently,theseovemdesareinputtothesystemthroughtactilecommands(；.e.pushingbuttons.turningknobsforpotentiometers,oradjustingmechanicaldevices).Sincetheoperatormonitorstheprocessprimarilyvisually,hemusteitherlookawayfromtheprocesstofindtheproperbuttonorknoborrelyon“muscularmemory”muchasatouch-typistdoes.Inthefirstcase,thetimeofresponsetoadeviantconditionmaybeexcessive.Inthesecondcase,thereisanincreasedprobabilityofasecondaryerrorbeingintroducedbytheoperator.Avoicerecognitionsystemcouldreducetheresponsetimerequiredfromtheoperator.Theprobabilityofpushingthewrongbuttonshouldsimilarlybereduced.Also,operatorfatigueshouldbeminimized.Sincetheoperatorcancontinuouslymonitortheprocessduringoverrideinput,theeffectofthechangecanbeobservedmorequickly.Thus,ifthedesiredvalueisexceededandreversecorrectionisrequired,itshouldbeaccomplishedmorequickly,allowinglessovershoot.Thisreductioninoscillationaboutthedesiredvaluemakesthesystemmorestable.Anotherfactorthatcanbeimprovedisoperatorsafety.Inasafety-criticalsituation,therobotsoperationcanbehaltedimmediatelybyuseofthe“emergencystop,orE-stop,mode,whichisinitiated,conventionally,bydepressingalargebutton.Ifanoperatorinadvertentlyfindshimselfinahazardoussituation,itmaybenecessaryforhimtoinitiatetheE-stopsequence.Shouldtheoperatornotbewithinreachofthebutton,however,hemaybeunabletotakethenecessaryaction,and,asaresult,couldsufferseriousinjury.HavingthecapabilityofstoppingtherobotbyissuingavoicecommandcouldsignificantlyimprovetheoperatorssafetybyenablinghimtostoptherobotevenwhennotwithinreachoftheE-stopbutton.Manualcorrectionsareoccasionallyrequiredtoadjustthelocationatwhichtheweldfillerwireenterstheweldpool.Properentrylocationisabsolutelycriticaltosoundweldquality.Adjustmentsaremadeeitherbymanuallyadjustingmechanismsthatholdthewirefeedguidetubeorbyissuingtactilecommandstoaservomechanism.Useofavoicerecognitionsystemcouldeliminatetheneedfortheoperatortoplacehishandwithintheworkingenvelopeoftherobotendeffectoror,ifservomechanismsareemployed,couldimprovespeedofresponseandstability.Anotheraspectofrobotoperationinanindustrialenvironmentthatisveryimportantisthesecurityofaprogrameditingcapabilityofthesystem.Undernocircumstancesshouldanyunauthorizedpersonbeabletoenterthisprogrammingmodeandaltertherobotsprogram.Avoicerecognitionsystemcanprovidethenecessarysecuritybyallowingaccessonlyforindividualswhoareauthorizedandwhosevoicescanbeidentifiedbythesystem.BackgroundRoboticweldingisunderdevelopmentbyNASAandRocketdynefortheautomationofweldsontheSpaceShuttleMainEnginethatarepresentlymademanually.Theprogrammabilityofarobotcanreducethepercentageofweldingdefectsthroughacombinationofconsistencyandrepeatabilityunattainablebyitshumancounterparts.Todothis,therobotisprogrammedtoanominalweldpathandlevelofweldprocessparameters(i.e.,current,travelspeed.voltage,wireadditionrate).Someadjustmentofthesevaluesisoftennecessaryduetoconditionschangingduringtheweld.Ahumanmakingamanualweldaccomplishesthisadjustmentreadily,whilearobotmustrelyonthelimitedtalentsofsensorsandtheabilityoftheoperatortooverridefunctionswhennecessary.SystemIntegrationThebasicelementsoftheworkcellsystemareshowndiagrammaticallyintheillustration.Theultimategoalofthesystemdevelopmentworkinprogressistogeneraterobotmanipulatorprogramsandweldprocessprogramsoffline,downloadthemtotheworkcellsupervisorycomputer,thenusesensorsubsystemstomakeclosed-loopcorrectionstotherobotpathandprocessvariables.OfflineprogrammingisbeingdonewithanIntergraphmodifiedVAX780/785-205computersystemwithInteractcolorgraphicsworkstations.Deviationsbetweentheprogrammedrobotpathandtheactualrequiredpathareobservedandcorrectedbyasophisticatedvision-basedsensordevelopedforthisapplicationbyOhioStateUniversity.Thissensorsystemisalsodesignedtopermitmeasurementofthemoltenweldpoolsurfacedimensionsandcorrectwe