ai-aerospace/ams_data_full_2000-2020 huggingface dataset:
Figure7:Postheattreatgeartooth crossectionFigure 8:Toothcrossection afterlOx predicted Failure Load andapproximates thecasestructure. Thetoothwidthatthepitchlineinthispictureisapproximately 0.8 mm(0.032in). ToothStrenqth Toothstrength (bending andcase)wasverified viastaticloadtesting. Staticloadtestingwaspertinent to thisdesignsincetherewouldbelessthan100peaktorquetoothhitsduringunitlife,allowing yieldtobe usedinmargincalculations fordesignlife.Theplanetgearcontact ratiowasestimated at1.3andayield of300ksiwasassumed basedonawelldefined relationship between material hardness andultimate tensilestrength (UTS). AnRc60material hasanUTSofgreater than330ksi,forwhichtheyieldwas estimated as90%oftheUTS.Theresultofthestaticloadtestingshowed notoothdeformation at5 timestheestimated singletoothinbending limitatyield.Atapproximately 10timesthesingletooth bending limit,onegearfailedatafixturerequired square keyway notch(Figure 9).Thetoothcontact area,uponsectioning, showed somemajordeformation andacrackinitiation (Figure 8).Asupposition couldbemadethatthecrackandsomeorallofthedeformation cameaboutasaresultofthefailed keyway section andanon-centered gear-to-gear rotation. Thefailedgearhadafixedcenterandthe othergearallowed rotational input.Thisexercise provedthatthehandcalculations forsingletoothin bending strength, combined withthegeometric contact ratio,wereveryconservative inastaticcase(bya factorofatleast5).Italsoshowed theheattreatcondition allowed adequate ductility whileproviding the required surface hardness tocarrythecontact stress. Thefinaldesignlastpassgearsetwastested dynamically at203N_m(1800in-lb)outputfortheequivalent of100torquetoothhitspertooth(onthe sungear)withnodamage ordegradation. Thepredicted lowestdesignmarginofsafetyforasingletooth inbending at203N,m(1800in.lb)basedonhandcalculations was0.249. Duringthecombination of actualQualandDeltaQualtesting, theQualunitsaw-125% ofthenumber ofcyclesoriginally slatedfor thecomplete Qualprogram. Also,onetestequipment glitchresulted inameasured 271.2N,m(2400 in.lb)outputfromtheBMAforaveryshortduration duringtheQualprogram. Thesestatistics further provetheadequacy oftheoverallgeardesign, andtheproofthatPyrowear _mettheanticipated strength anddurability required bythisprogram. WormDrive Thewormdriveultimately provedtobethemostchallenging partoftheBMAdesign. Agreatdealof effortwasspentproving outthewormdesignearlyintheprogram. EarlyBMAdesigns considered many different alternatives totheMOdrivesystem, butbecause thespecification fixedtheoverallpackage size, andrequired oneofalimitednumber ofMOinputtorqueandspeedoptions, therewerenotmany practical alternatives toconsider. Anyattempt toeliminate thewormdriveconcept addedmany additional partsandcreated adifferent setofunknowns. Again,because ofenvelope constraints, there 82
] 9:Planetgearstaticloadtestfixture J / wasinsufficient roomtopackage boththeneeded hardplanetary ringgear,anddesired (traditional) soft wormgearsincetheyhadtobecontained onthesamepart.Thisdrovethedesigntothe"hardonhard" (HOH)approach. WhiletherearemostlikelyHOHwormdesigns thathavebeenusedinthepast,they arenotwelldocumented. Inaddition, therewasnowaytoincorporate anytypeofenclosed "gearbox" to retainagreaseoroilbathatthewormsurface. Thetemperature rangeof-54°C(-65°F)to71°C(160°F) inavacuum alsoseverely limitedthelubricant choices. Withthesedesignparameters (theyseemed morelikeroadblocksinthebeginning) inmind,the development program forgedahead. Thefollowing sections listthestepstakenanddetailslearned in chronological fashion. EarlyWQrmEfficiency andStrenath Thefirstitemsthatneeded tobedetermined wereknowing thepractical staticloadlimitandefficiency (staticanddynamic) ofthewormdrivewithno,orlimited, lubrication. Theoriginal designwouldhave used440Cforboththewormandwormgearandthesewereputonorderasdevelopment units.Inorder togaindataasearlyaspossible, several standard 303CreswormsandBronze wormgears(hardon soft,HOS)wereordered fromBerg(#W24B37-D50, 24DP,3/8"FaceWidth,50Tooth,Alloy464Bronze gear,W24S-4D, doubleleadworm)asclosetotheactualBMAdesignaspossible. Fixturing wascreated andinitialstatictestingviahanddriveninputconducted. Statictestinginvolved connecting theoutputof thewormsystemtoground (fixed)oramagparticle brake(slowdynamic). Theresultsshowed thatthe rangeofefficiencies obtained couldbesubstantial. WormGearEarlyStaticEfficiency TestDataResults: Nolube-12.5%(HOS) HighPressure grease-21-39% (HOS) Everlube _3620C(molybdenum disulfide andgraphite epoxycoating) -45-56% (HOH) Earlyintheprogram, attheselected ME)ratioof12.17:1 ratioand28.2N,m(250in,lb)maxinput,the BMAhadtogenerate 135.6_+20.3N,m(1200_+180inolb)output. Thisfixedtherequired efficiency range oftheMOsystem from33.5to45.4percent overall. Everlube ®620Cappeared tomeetorexceed this needed rangerecpeatedly, thoughonthehighside,withnootherlubrication needed inthesimplified test setup. Everlube 620Cwastherefore selected asthebaseline lubrication. Wormgearultimate strength wasanother issuethatneeded tobedetermined. Sinceasingleenveloped wormsystem contains agearthatisnotanextruded involute profile,itdoesnotreadilyconform tosingle toothinbending equations. Also,typicalwormapplications areusedtotransmit horsepower (athigh speedandlowtorque) andarelimitedbythecooling capability ofthelubricant. Because thebasicworm designisdominated byslidingfriction, heatgeneration canbeamajorfailuremechanism. This 83
Wormandwormgear piecesweresenttoBalzers andcoatedwithWC/C.It wasimmediately apparent thattherelativelyshort break-inperiodadvertised wouldbeasignificantfactor inusingthisproduct.Ifhigh loadwasappliedatthe beginningoflife,theWC/C coatingwouldremoveitself fromthesurfacesthrough abrasivewear.Iftheload weregraduallyincreased anddecreasedin succeeding increments, with cooldownperiodsin betweenandperiodic cleaningandre-greasing withBraycote®601EF,the systemwouldstabilizeata 38to42percentoverall efficiency.Theworm surfaces,oncebroke-in wouldhaveamirrorsmooth finish,andtheefficiencywouldbealmostflatoverthe loadramprange.This turnedouttobethebestof allworldsfortheBMA design,andwasselectedas thebaseBMAdesign. LowTemp.LowTorque Noise Because theBMAuseda relatively coarseworm,an inputtorqueripple (oscillation) wasalways evident asthewormpicked upanewgeartooth(and waslessefficient) andthat toothpassed through the centerofthewormhelix (mostefficient point). DuringQualleveltestingatDev2at-65_" inboxpostau_acer removal TI_Ilain=:ml_m 01lnldm (elr¢TI_0 _ T 1"I_l0'!IBI!$;{)!U2!i"i_FII_IIQ{(p_lI_lXI_11Spll(Zt I1_fflOlll :c_-:::-- i.......I.............. _......|_..;_._ +"[_ j_ .... ......._.............. 1......_: ----'.....+1............ ....................................................................... k •,1_,,,i..=..-,Ir,_ld_-,r,'_t;,.-,: .:.:'..:_-::C:::-----'-:---.--:'."Z:-:::: :::__::,,p:::::: :__.'_,q.'l_. __r__,l_r_.: _gP.rj;,_¶ ::::::::::::::::::::::::::::::::: :::::::: :1:::::: :::::::,:::::::: ........ ::::::::::::::::::::::::: :::::::::::::::::::::::::::::::::::::::::::::::::::::::::: :::::::: :::::::I::::::::: ............................ I................................................ !!!i!:_!!E!!'-':!!t!!--'--]!?!--?!]!!!!!!!t!!!!!!!!_!! ...................... ........................ ::::::::::::::::::::::::::::::::: ........................ _.,_:.;_";_:..:;j".;_,;::: ::::::::::::::::::::::::::::::::: ..................... rm,r-"_'+,--"m._ -'mr,_,+-"t'J'+ 'b+,+_.+','_-" D S 10 16 2D 25 _ 35 40 45 eli Dev2at-65Tinboxpostauxhubspacerremoval ..... L.... Figure 10:LowTemp,LowLoadInputTorque Oscillations Nominal (top),andabnormal (bottom) -54°C(-65°F), itwasoccasionally noticed thatthelowloadpeak-to-peak inputtorquerequirement would increase substantially, moving fromanaverage torqueofabout1.7N,m(15in,lb)toanaverage ofas muchas3.4Nom(30in.lb)(Figure 10).Thisdidnotappeartobeaproblem atthattimeastherewasno directrequirement onhowlow,"low"torqueneeded tobe.However, ontwooccasions duringQuallevel testing, equipment problems resulted inateststoppage duringaMOperformance testattheendofthe forward ramporatthebeginning ofthereverse ramp.Eachtimethetestwasresetandre-runfromthe beginning, repeating the60forward revswithnoreverse revsplacedontheunit.Onbothoccasions, the forward rampefficiency inexplicably dropped tobelowtherequired 33.5%minimum. Whentheunitwas 85
immediately, andthreetimestheamountofgreasepreviously appliedwouldallow6ormorecycleswith noonsetoftorquenoise.Thefactthatthisonlyhappened at-54°Ccouldbeexplained bytheincrease in greaseviscosity. Withthegreasealmostpaste-like at-54°C,itwould"push"outofthewormsliding interface totheedgesofthewormandgear.Whentheunitwarmed up,thegreasewouldbecome soft againanddroopbackintoaction.Oncethesurfaces werere-coated atthehighertemp,theunitcouldbe takencoldagainandthegreasepushingactionwouldstartover. Fina.IDesiqnChange Because thedesignwouldworkrepeatedly near20°Candhigher,anditappeared afterofintensetrouble shooting at-54°Cthatthetorqueblooming mechanism wasunlikelytobefound,additional thermalfoil heaterswereaddedtotheunit.Withbothheaterchannels on,approx.44wattsminimum wouldbe available toheattheunitfrom-54°Cto7.2°C(+45°F,Quallevel)intheeventtheMOwouldbeneeded onorbit.Triplingtheamountofgreaseoriginally appliedinthewormareaalsohelpedthelow temperature operation. Thebenefitofadditional greasewasnotrealized untilaftertheadditional heaters wereaddedtothedesign. Thecombination ofthesetwofixesresulted inareliable, HOHmanual override mechanism. ¢5 = I'---E;/N001Test23HHCycle3@35to55 Ma_LmlOuI_EIdE I;Perf. TIl=:;_ * !_.. .......... .=,-:_t_ !_|....J..... L--- I....... 1.................. .......... =;"- t.....J......:::::::::::::::::::: looo InputspeedtoMO .................... --"'-_"_T-_ i_'=1 r.............. 48  ........:::::::::::::::::::::::: ::i::::::::::::::: .....:........................... ..f,,................. 40 800 .._-J, _" _I _----_L.-_--1 Efficiency ------_--------'---Z_-__--ZZZZZZZZZZT)ZZJZZZZZZZZZZZZZZ %:llll ..f_- ................. 32 ooo .........................................,'---El------lillE- --Z--El--_" .......................................... 24 o o 14,50 14.67 14.83 1_5.00 15.17 Time,minutes Figure 11:Example ofaBMAtorque rampprofile Figure11showsthebasicinput(darkblue)andoutput(pink)torquefortheBMAMOsystem. The efficiency curve(lightblue)showshowtheefficiency comesupquicklyasloadtorqueisappliedand staysinthe40%rangeduringtherampperiodthrough 135.6N-m.TheinputspeedcurvetotheMO (green)showsarangefrom48-50rpm.Thewormshaftspinsin162rpmrange. BriefMention ofOtherItems Severalotherlessonslearnedwereworthmentioning butwillnotbediscussed indetail.Theseinclude thefollowing: 87
Retainer Rinqs MS27426 retainer ringswereusedtoholdthecarrierplanetpinsintheplanetary system. Theringswere usedonlyoninternal grooves andarecomprised oftwoalmostcomplete revolutions offlatstock,witha steptransition fromthelowerlegtotheupper. Unknown toEngineering earlyintheprogram, assembly tookplacewithpreviously used(anddistorted) rings.Whencombined withtheneedlebearing issue discussed above,acombination ofplanetpinrotation, axialneedlebearing loadsandpreviously used retainer rings,caused theringstojumportwistoutoftheirgrooves. Thiswasfurtherexacerbated by smallinterruptions intheretainer ringgroove, caused bythegeometric intersection oftheplanetpin bores,whichgavearotating ringachance toexititsslot.Byeliminating there-useofanyretaining rings thisproblem wasresolved sinceanundeformed ringwouldnotcomeoutofthegroove, evenifrotating. Conformal Coat Theelectronic boardsweredesigned tobeconformally coatedwithalowoutgassing material called Conathane CE-1155. Astandard military gradesilicone coating (DowComing 1-2577) wasinadvertently applied toseveral boards. Sinceseveral components ontheboardweresilicone based,usingasilicone stripper toremove thecompound wasdeemed ahighrisk.Sincetheleadtimetoreplace someofthe electrical components wasontheorderof52weeks, anattempt wasmadetovacuum bake-off the outgassing components ofthesilicone material. Thefinalconclusion reached wasthat180hours vacuum bake(<1E-5Torr)at82degrees Creduced theoutgassing levelstoprogram requirements. Conclusions Theprimary focusofthispaperwastoconvey thesuccessful designandimplementation ofaHOH,high torquewormdriveusingPyrowear 675_,WC/CandBraycote _601EF. Empirical testinghelped substantiate theultimate loadcapability offinepitchgearing andwormdrives,whichwerevaluesnotwell documented orreadilydetermined analytically. Theunderstanding oflowtemperature applications of Braycote 601EF, asrelatedtotheslidingenvironment ofawormdriveanduncaged needlebearings, was alsofurthered bythisstudy.Andfinally,adetermination ofhowtosuccessfully heattreatPyrowear _675 wasobtained. Inthefinaldesign, theBoltMotorActuator program successfully incorporated several newtechnologies andovercame significant hurdles. Thedelivered product metthedesignchallenges setforbythe specification inaveryrobustpackage. Itisbelieved thatseveral ofthetechnologies discussed inthispapercouldbeusedtobenefitthespace mechanisms community. 1Kapton®isaregistered trademarkofE.I.DuPontDeNemours &Co.,Inc.U.S.A. 2Pyrowear® isaregistered trademarkofCarpenter Technology 3Everlube _isaregistered trademark ofGreatLakesChemical Corp. 4Braycote _isaregistered trademark ofCastrol Incorporated 88
wereprimarilydueto(possiblynonlinear)stiffnessanddamping,andtheinertialcomponent duetothe glove'smasswassmallenoughincomparison tobeneglected. Theseassumptions allowedasubstantial simplification ofthesystem.MCPjointstatecouldbe measuredwithasinglesensor:apositionencoderorpotentiometer monitoringtheextensionoftheMCP drivecable(withvelocityderivedbydigitalfilteringornumericaldifferentiation). Thissensorcouldbe external,locatedintheactuatorbodyonthebackoftheglove.Amappingofjointstatevs.resistance torquewouldbeneeded;onceestablished inalookuptablethecontrollingmicroprocessor couldquickly calculatetheappropriate torqueforanystate.Sinceinertialforceswerebeingneglected,noacceleration feedforward oranticipation ofoperatormotionwouldberequired. Duetothelargenumberofunknowns,itwasdecided toapproach theultimate goalofaflight-qualifiable unitinaseriesofsteps.Thefirst(MkI)unitbuiltwouldbeusedinalaboratory settingtotestthe assumptions made--a proof-of-concept. Thecriticalissueswereperformance andactuator packaging. Therequirement tooperate invacuum andunderwater wasrelaxed, andalaboratory powersupplyand desktop personal computer wereusedinstead ofminiaturized, self-contained components. Powerand datasystems ofeventual flightunitswouldbelocated inthePLSS--a morestraightforward packaging problem thatcouldbepostponed toafuturedesigniteration. Commercial off-the-shelf (COTS) components wereusedwherepossible tospeedthedevelopment. Anumber ofactuation technologies wereexamined forsuitability including pneumatics, hydraulics, "memory-metal" wires,phase-change actuators, andvoicecoils.DCservomotors werechosen fortheir precise controllability, speedofresponse andcompact packaging. Tosimplify thedesignofdriver electronics, abrushed DCmotor(InlandMotorsQT-1106) wasselected fortheMkIunit.Anop-amp current drivercircuitwasconstructed toenablethemicroprocessor (aGateway 200080486-based personal computer) todirectly command motorcurrent, whichisproportional totorque. "1I Optical Encoder_,_,. iiO,,-I 1 !-t ___, Electrical Connecto4_,,,,,, !' ._--.,'.DriveCable J  C_bieSpool Figure1.MkIActuator Themotordrovethecablecapstan through a2.5:1single-stage spurgeartransmission. Thecablewas secured tothe4.7mm(0.185in)diameter vertical spool,thenproceeded around the0.635cm(0.25in) diameter horizontal shaftofa2-channel digitalincremental opticalencoder (Bourns ENS1JB28L00256), thenontotheMCPjointattachment. Multiple wrapsandpassage through atransverse holeinthe encoder shaftprecluded cableslippage ontheencoder shaft.Allrotating components weresupported by ballbearings. 92
Gloveforceswerefoundtohavesignificanthysteresis. Theforce/position mapobtained intheopening direction differsfromthatintheclosing direction, asshowninFigure2.Evenwhenstationary, theforce required tomaintain agivengloveposition depends onthepriordirection ofglovemotion. 80, 704 oo]g5o "30I20I I I )/ jJ if_" ./f tj / ...// ,J 01......... I I.......... ! I 0.0 0.5 1.0 1.5 2.0 Cable Contraction (cm) [--- Force(Closing) --Force (Opening) I2.5 Figure2.MkIGloveForce/Displacement Curve Thisrequired thecontrolsystem torecordandutilizetwoforce/position maps;oneforeachdirection. A "transition strategy" wasdeveloped byDr.Sanner tosmoothly handlechanges ofdirection, without exciting oscillation. Thisalgorithm isdescribed indetailin[8]. Whenthesystem wasworking stablyonthebench,development continued usingagloveboxatILC Doverandavarietyoftestsubjects. Withanoperator's handintheglove,anumber ofsubjective phenomena werenotedwhichwerenotevident onthebenchtop. Thisphaseoftestingwascloseenough toanoperational scenario thatsomeofthebasicresearch questions couldbeanswered. Thefirstobjective wastovalidate orrejectouroverallpower-augmentation approach. Thethree assumptions madeinthedesignprocess weretested. Thefirsttwoimplied thatMCPjointtorque depends onlyonMCPjointstateinthenewglove.Wehadbeenforcedtomodifythisabitalready when theglove's hysteresis wasmeasured. Torque evidently depends somewhat onpaststate(direction of motion) oftheMCPjointaswellasthecurrent state.Thisadjustment hadbeensuccessfully dealtwithin software. Withfullcompensation formeasured cableforces,minorvariations inactualglovetorqueinevitably cause someerrorinthecounter-torque applied. Whenthecompensation torqueswitches frombeingan underestimate toanoverestimate theglovesuddenly opensasmallamount, anditclosesasmallamount whenthereverse happens. Operators foundthis'bncommanded" glovemotiondistracting. Thesystem wasjudged lessintrusive whenthetorquemapswerebacked offabitfromfullcompensation. Allerrors wouldthenbeintheundercompensated sense,and"uncommanded" motionwouldnotoccur.The disadvantage ofthiswastosomewhat increase thegloveforcesmaking itthrough totheoperator's hand, diminishing theeffectiveness ofpoweraugmentation. Themagnitude ofthiseffectdirectly addresses thefirsttwodesignassumptions. Anydependence of MCPjointtorqueonfactorsotherthanMCPjointstatewouldresultincompensation errors. Ifthese errorswerelarge,thelevelofcompensation wouldhavetobescaledbackproportionally. Iftheoriginal assumptions madewereincorrect, theremaining compensation wouldaccount foronlyasmallfraction of thegloveforces,andthesystem wouldnotsignificantly easeglovemotion. 94
Figure3showstheresultsfromabenchtopexperiment inwhichtheauto-calibration procedurewasrun withcompensation turnedoffandon.Itshowsthatthecompensation systemreducedgloveforce (measuredattheactuationcable)fromapeakofover64N(14Ibf)toaround4.5N(1Ibf),areductionof over90%.Thus,theassumption ofMCPtorquedependence primarilyonMCPstateappearsjustified. 70] I 6o I 5o  i°ol 2°l lo}! 0I.....,--.-._'"T T I 0.0 0.5 1.0 1.5 CableContraction (cm I--- Force(Compensation On)_gorce (Compensation Of_2.0 Figure3.MkIGloveForceWithandWithout Compensation Thethirdassumption, thatinertialglovetorquewasmuchlessthantheposition- andvelocity-dependent torque, couldalsobetestedusingtrajectory datafromtheworking MkIsystem. Theequivalent inertiaof theglovewasfoundtoberoughly 625_(1.4lbm_asseenbytheactuator cable.Atthemaximum desired cableacceleration of650cm/s(256in/s)thisgivesrisetoa4N(1Ibf)inertialdisturbance force; comparable inmagnitude totheotheruncompensated gloveforces. Sincethispeakinertialforceisless than10%ofthetotalgloveforce,ourfinalassumption appears justified aswell.Thetopicofextrainertia introduced intheactuator isdiscussed laterinthesection onMkIIactuator design. Extensive physiological testingdocumented in[7]and[8]compared fatigue(measured byEMGsignal analysis andbydecline inMCPrangeofmotionovertime)foranumber oftestsubjects performing repetitive taskswiththecompensation system turnedoffversuson.Itwasfoundthataverage taskeffort decreased 30-40% withthepoweraugmentation. Thesystem alsoenabled allsubjects, someofwhom hadapoorfitintheglove,toutilizefullmobility oftheMCPjoint. Somedeficiencies intheMkIsystem became clearastestingproceeded. Theactuator dissipated quite abitofheat.Afterfifteenminutes ofhardoperation, theexternal housing temperature wouldreach93°C (200°F), afterwhichperformance woulddegrade duetointernal dimensional changes. Nodiscomfort wasnoticed insidetheglove,however. Occasional "glitches" (uncommanded motion) wouldoccurinoperation. Someoftheseappeared tobe theresultofactuator internal frictionchanging withtemperature (leading tocompensation errors)and someweretheresultofslackinthecable(leading toerrorsingloveposition estimation). Cableslack wasseentooccurwhentheoperator opened his/herhandveryquickly; therewasatimelaginthe actuator's response. Insummary, thetestingoftheMkIactuator andgloveestablished theSSUILC poweraugmentation approach asaviableone.Theactuator metitsperformance andpackaging goals,andthetestdata refinedourphysical understanding oftheproblem. Subjectively, thesystem madeadramatic difference in taskeffort.AsILCandSSLpersonnel gainedexperience withthecompleted system, several ideasfor improvement inbothgloveandactuator designemerged. Theseideasledtoasecond designiteration. 95
objectionable resistancetomotion(gloveclosing). model: F-_Thiscanbequantifiedusingthefollowingtwo-mass T MG=MassofGlove MA=MassofActuator T=Tension inCable I;=Tension inCablebetween Masses F=Forceapplied byfingerstoinitiatemotior x=Position ofGlove y=Position ofActuator Thissimplified modelassumes thecableisperfectly stiff,andthattheactuator controllawexactly compensates theglovestate-dependent forces('risequalonbothsidesofthediagram). Thesystem dynamics arethen: MGY,=F+'_-T MAS/=T -z Sincethecablecansupport tension butnotcompression, x=yif1;>0.Thiscondition isviolated whenI; goestozero.Solving for1;: M.___G(T-1;)=F+1;-T MA --_'t"=T-MAF MG+MA Sothecabledevelops slack(1;=0)when: +,T or F> T wheretheeffectofspoolsizeisincluded. Forsmooth gloveoperation, therefore, itisdesirable to increase themagnitude oftherightsideoftheaboveequation abovethelevelofexpected human operator inputforces. Somedesign-relevant conclusions canbedrawnfromtheabovemodel. Parameters TandMGarefixed bytheglovedesign. Tomeetotherobjectives, glovedesigners strivetominimize bothofthese quantities. Inparticular, agoalfortheMkIIglovewastoreduceT(themagnitude ofthegloveresistance force)byatleast30%belowtheMkIlevel,whileMGwaslikelytoremainthesame.Thus,slack occurrence wouldbeamoreserious problem withtheimproved glove. Cabletension Tisafunction ofMCPjointposition, goingtozeroatthefully-closed position. Slackis therefore moreproblematic inthatvicinity. Tocombat thiseffect,somebiasforcecanbeapplied bythe 97