TheconceptoftheSSL/ILCpower-assisted gloveistwo-fold.Thefirst(ILC)taskwastodesignaglove withanMCPjointwhosemotioncouldbeisolatedfromtherestoftheglove,andaclosed(grasped) neutralpositionwhenpressurized. Anattachment pointforanactuationcableonthedorsalsideofthe MCPjoint,andaconformalmountingplateforanactuatoronthedorsalsideofthehandwerealso required.Thesecond(SSL)taskwastodevelopasmallactuatorwithrapidresponseandsufficientforce andstroketoallowfullmobility.Theactuatorapplies tension toacable,whichsupplies opening torque fortheMCPjoint.Theactuator applies forceonlyintheopening direction; sufficient closingforcesare inherent intheglovedesign. Thisapproach keepsthepalmareaofthegloveclearofextramechanisms. Actuator System Requirements Theroleoftheactuator subsystem inthepower-augmented gloveistosupplyappropriate tension tothe drivecable.Itneedssufficient sensors todetermine thecorrecttorque, amechanism forsupplying the torque, andasuitable controlalgorithm. Todesignanactuator mechanism, onemustknowthedesired force,stroke,velocity, acceleration, packaging andpowerlimitations, andtherequired operating environment. Inthiscaseactuator design proceeded concurrently withdevelopment ofthenewglove,sodesignworkoneachhadtobeginwithout detailsoftheothersystem beingavailable. Conservative assumptions weretherefore made.Theglove designers wereaskedtogiveusthelargestmounting areatheyreasonably could,andwewereaskedto designtotheworst-case gloveforceestimates. Frequent communication kepteachgroupawareof updates astheycamealong. Maximum gloveforceswereinitiallyestimated fromexperimental measurements onexisting Advanced Development PhaseV(improved 5000series)glovesandsometheoretical workonthenewdesign (whichusedanunjoined rollingconvolute) tobeabout31N(7Ibf)atthecable.Cablestroke corresponding tothefullrangeofroughly 50°ofgloveMCPjointtravelwasestimated at2.5cm(1in), fromthegeometry ofthepreliminary glovedesign. Maximum rateofdesired MCPjointmotionwas derived fromatypical"nude-body" maximum performance rateof4cyclespersecond fromfullyopento fullyclosedandback.Inthismotion, theactuating cabletraverses itsfullrangein1/8second. Assuming constant acceleration for1/16second, andconstant deceleration for1/16second, theacceleration value required atthecableis650cm/s2(256in/s2).Themaximum required velocity forthecableis41cm/s(16 in/s). Severe packaging constraints applytospacesuit hardware. Poweraugmentation mustbeaccomplished without addingobjectionable bulktothegloveorrestricting dexterity. Thesameworkenvelopes currently specified byNASA[9]mustbeusablewiththeaugmented glove.Amounting location onthebackofthe handwasidentified whichwouldnotinterfere withtheotherglovedegrees offreedom orviolateNASA workenvelope constraints, Thisvolume wasroughly 7cm(2.75in)longitudinal by10cm(4in)lateralby 3.2cm(1.25in)tall.Evenwithinthoselimits,itwasstrongly desired tokeepactuator volume toa minimum, sincefutureapplications mayrequire multiple actuators ontheglove.Somecomponents ofthe system (e.g.powersupply, microprocessor, etc.)couldbelocated remotely inthebackpack (PLSS). Safetyisaprimeconsideration inspacesuit systems. Thisconcern ledtotherequirement ofno penetrations ofthepressure bladder forthissystem; allcomponents mustbeexternal. Thissystem must alsoavoidcreating ahazardous temperature insidetheglove.Amaximum temperature riseatthebase oftheactuator (backofglove)of40°C(72°F)overambient (poweroff)wassetasalimit.Thesystem mustbedesigned tofailsafe.Specifically, nocredible failuremodecancompromise theintegrity ofthe pressure suitorprevent theoperator fromperforming themanual tasksneeded toingress theairlock. Nostrictlimitonpowerrequirements wasinitiallyset.Aneventual flightsystem mustprovide sufficient powerforasix-hour EVAduration, andbeabletorejecttheheatdissipated internally. Thedesignintent atthisphasewastominimize powerconsumption giventherequired performance andotherconstraints. 9O