Ultimately,thesystemwouldberequiredtoworkinseveralenvironments: thelaboratory(airatsea-level pressure,roomtemperature), NBS(immersion inwaterat32°C(90°F),upto255kPa(37psi)pressure), andspace(vacuum).Diversafetyrequirements inNBSledtoamaximumvoltagerestrictionof30V. Development oftheMkIActuator Principle ofOperation Abasicscheme ofoperation wasneeded first.Howwouldtheactuator determine whattorquetoapplyat anygiventime?Oncethiswasdecided, component selection anddetailed designcouldbegin. Several possible schemes werereviewed fromtheliterature andourinitialdiscussions withILCDover. Thefirstisthemostdirect:sincethegoalistoreduceforcesbetween thegloveandthehand,measure thoseforcesandcontroltheactuator todrivethemtozero.Afundamental problem withthisapproach is discriminating between intentional forces(suchaswhengripping atool)andtheunintentional ones caused bygloveresistance. Another problem issensorplacement. Eitheryouviolatethepressure bladder orplacetheforcesensors between thebladder andtherestraint layer,wheretheywouldalso reacttoinflation pressure. Sinceaforcesensormusteffectively beinserieswiththegloveandhand(all oftheforcesbetween thegloveandhandmustgothrough thesensor), alargesensorareaisrequired, causing furtherpackaging difficulty. Thesecond possibility isaposition-control scheme: sensors ontheoperator's handcouldmeasure joint positions, andtheactuator coulddrivethegloveposition tomatch. Position sensors couldbemuchmore compact thanforcesensors sincetheyoperate inparallel (itisjustnecessary tomeasure position atone placeonajoint).Unfortunately, thereisthesameproblem whenthehandmakesintentional contact with anobject. Theactuator wouldrejectthosecontact forcesasdisturbances, uptoitsmaximum torque capability. Theoperator wouldn't knowthatheorshehadcontacted anything untiltheactuator was overwhelmed. Bythen,excessive forcesmighthavebeenexerted onadelicate component. Also,again, sensorplacement isinviolation ofthepressure bladder, andsensors ontheastronaut's handwould furthercomplicate the(already lengthy) spacesuit donanddoffprocedures. Someoftheproblems withthesefirsttwoapproaches couldbesolvedbyaddingforcesensors tothe outside oftheglove,andusingtheactuator todrivetheglove-hand forcetoequaltheglove-external objectforce.Theoperator wouldthenbeabletosenseandcontrolcontact forcesappropriately, whilethe actuator tookcareoftheglove-originated forces. However, multiplicity ofsensors isaserious obstacle to theimplementation ofthisscheme, andanother isthatitisunstable inthe1-glaboratory environment (consider whathappens whenthehandisrestedonatable). Another ideacommonly discussed inthepoweraugmentation community istheuseofelectromyographic (EMG)sensors tomeasure muscle stimulation. Ifanaccurate mapping between thesesignals andjoint motioncouldbedeveloped, thepotential existsforthegloveactuator toactasanextra"muscle" responding tothesamesignals astheoperator's ownmuscles. Iftunedcorrectly, theactuator would movethegloveinsynchronism withtheoperator's hand.Unfortunately, thistechnology isnotyet sufficiently developed. EMGsignals arenoisyand,duetothecomplexity ofmuscle/nerve systems, only giveacrudeapproximation ofjointmotioncommands. Theyareusefulforcharacterizing grossmuscle parameters suchasfatigue(seetheResults section) butwerenotconsidered practical forthefinelevelof controldesired inthisapplication. Theaboveapproaches wereadmired fortheirgenerality butfoundunsuitable andover-complex forthe problem athand.Itwasnecessary tomakesomesimplifying assumptions abouttheproblem, which couldbetestedwhenhardware wasbuilt.First,itwasassumed thattheglove's forcesderivefromits state(DOFconfiguration andvelocities) inarepeatable manner. Second, itwasassumed thatthenew glovedesignwouldsufficiently isolateMCPmotionsuchthatMCPtorquewillonlydepend onMCPjoint state.Theanglesofthefingers, forinstance, wouldnotsignificantly influence theglove's torquearound theMCPjoint,andsocouldsafelybeignored. Third,itwasassumed thattheglove's resistance forces 91