ai-aerospace/ams_data_full_2000-2020 huggingface dataset:
/:/ / MIROCalibration Switch Mechanism JasonSuchman*, YukiSalinas* andHollyKubo* Abstract TheJetPropulsion Laboratory hasdesign, analyzed, built,andtestedacalibration switchmechanism for theMIROinstrument ontheROSETTA spacecraft. MIROistheMicrowave Instrument fortheRosetta Orbiter; thisinstrument hopestoinvestigate theoriginofthesolarsystem bystudying theoriginof comets. Specifically, theinstrument willbethefirsttousesubmillimeter andmillimeter waveheterodyne receivers toremotely examine theP-54Wirtanen comet. Inordertocalibrate theinstrument, itneedsto viewahotandcoldtarget.Thepurpose ofthemechanism istodiverttheinstrument's fieldofviewfrom thehottarget,tothecoldtarget,andthenbackintospace.Thiscycleistoberepeated every30minutes fortheduration ofthe1.5yearmission. Thepaperdescribes thedevelopment ofthemechanism, aswell asanalysis andtestingtechniques. Figure 1.CADModeloftheMIROCalibration Switch Mechanism Design Thedesignfeatures astepper motorwithplanetary gearhead manufactured byCDAIntercorp. Thepower istransmitted fromtheoutputshaftofthegearhead toaflexcoupling madebyHelical Products Company, Inc.Theflexcoupling ispinned toboththegearmotor's outputshaftandashaftthatruns acrossthemechanism toabracket thatholdsacounterweight andtheSMApinpuller byTiNiAerospace, Inc.ThepinoftheSMApinpuller engages thesideofthemirror,whichisheldinplacebyVesper_SP-3 journal bearings onthetransverse shaftdescribed above. Vespel_SP-3isalow-friction polyimide manufactured bytheDuPont Corporation. Themirrorisunderamoment loadduetoatorsionspringthat, whentheSMAPinpuller isactuated, slamsthemirrordowntowards thebracket andagainst aVespel_' SP-3hardstop. Theoff-axis massofthemirror isbalanced bythemirror counterweight. All counterweights aremanufactured fromtungsten class4(MIL-T-21014) toprovide ahigh-density material tominimize volume, whichwouldadversely effecttheconfiguration. Feedback totheMIROcomputer is provided bythreeInfrared reflective objectsensors thatprovide information astotheposition ofthe mechanism. Upontesting oftheinstrument wefoundthatusingthesesensors inthisconfiguration was troublesome, andthepaperwilladdress thisissueaswellaswhatthecorrectimplementation shouldbe. Figure2showsa25pinconnector; however, thisconnector wasremoved duetomassconsiderations, andapigtaildesignwasadopted. "JetPropulsion Laboratory, Pasadena, CA 179
..°- -°. PINPULLER COUNTERWEIGHT Figure2.Overall Configuration oftheMIROCalibration Switch Mechanism Onecomplexity ofthesystem wasitsneedforarepeatable failsafe device. Ashapememory alloy(SMA) pinpuller, developed through apartnership between TiNiAerospace, Inc.andJPL,waschosen toperform thisfunction. Thepinpuller features aprimary andaredundant circuittoprovide addedreliability. The deviceisgoodforsmaller applications whereasmallstrokeandasmallpullforceisadequate. Another consideration inselecting thisdevicewasitscleanliness. Agreatdealofhighprecision instruments arein verycloseproximity tothemechanism, sooutgassing ofmaterials andlubricants isofgreatconcern (total massloss<1%;volatile condensable mass<0.1%). 180
i: iiiii!iiiii!!!ii  ii!ii !!iiiiiiiiii    i iiii¸¸¸i ThePinpuller is activated, allowing the mirror(shaded gray) torotate independently. The pinpuller ispushed against ahardstopon thebracket asthe mirrorispushed towardthesafe position bythereturn spring.TheMirrorisrotated against theRTVstop (onthefarsideofthe mirror)inthesafe position. Thereturn springwillkeepthe mirrorinthisposition indefinitely.TheFail-safe Mechanism isresetby drivingthepinpuller arounduntilitcanreengage themirrorin thesafeposition. Duringtheresetcycle themotormust overcome thetorque ofthereturnspring andthefrictionatthe pinpuller/mirror interface caused by thepinpuller pin extension spring. The mirrorlipisangledto allowthepinpuller to engage themirror moreeasily._,iThePinpuller isfully resetandthe Calibration Switchis fullyoperational. ThePinpuller isreset intheeventthatthe pinpuller isdislodged fromthemirrorduring launch, orifthemotor beginstooperate againafterthe Failsafe hasbeen activated. Figure 3.Sequence ofoperations forpinpuller failsafe actuation andreset Testing Testing ofthedevice included acceptance testing oftheexternally provided components aswellas qualification testing ofthecompleted mechanism. Thetestenvironment includes temperatures of-30to 60°C(operating) and-40to70°C(non-operating). Thedynamics environment included sinevibration in allthreeaxes(5.0Hzto21Hz=+7.5mm(0topeak),21Hzto60Hz=13.5g,60Hzto100Hz=4.0g) aswellasthreeaxesofrandom vibration (20Hzto100Hz=+3dB/Oct, 100Hzto300Hz=0.05, (M+20)/(M+I)*g2/Hz, 300Hzto2000Hz =-5dB/Oct). Thevastmajority oftheenvironmental testingwas performed attheMIROinstrument level. Thelifetestingofthedevicewasperformed aswell.Thelifetestcycleswerecalculated byadding two timesthenumber offlightcyclesplusfourtimestheanticipated ground testcycles, whichresulted in 52,790 cycles. Thelifetestendedafterover250,000 cycles,farinexcess oftherequirement. However inspection ofthetestsetupshowed thatthefailedcomponent wasthemotordriverelectronics, aground support equipment non-fiight component thatsimulated theflightelectronics. Uponfurtherinspection of thetestsetup,itwasnotedthattheseelectronics, aswellasthemechanism itself,wereboltedtoa plexiglass base.(Wethought itlooked nice!)Unfortunately plexiglass canaccumulate astaticcharge fairlyeasily,butasitisnotagoodconductor ithasdifficulty gettingridofthischarge through grounding. Therefore wefeelthatelectrostatic discharge probably occurred andendedourtest.Figure4shows somephotographs ofthetestsetup. 181
Figure4.LifeTestSetup Thefinalmechanisms havebeenbuiltandtwoflightworthy units(flightandflightspare)havebeen delivered totheproject.Theflightmechanism hasbeenintegrated intotheflightmodelforMIRO.Rosetta isscheduled forlaunchinJanuaryof2003. Figure5.Photoofthemechanism duringlifetest 182
temperatures themirrorwasdetectedbysomesensorsapproximately 5degreesawayfromthedesired position.Inmyopinion,wepickedthewrongsensorforthejob.Thataside,wedidnotimplementthe sensorswechoseinanappropriate way.Insteadofdetectingtheentiresideofthemirror,weshould haveplaceda10-mmlongdowelpinnormaltothesurfaceofthesideofthemirror,withitsendpolished. Therefore,thesensorwouldonlyseethepinwhenitwasplacedinfrontofitsnose,butwhenthepin movedoutofthewaythesurfacethatisleftwouldnotbeatanappropriate focallengthforgoodsensing. Butwefeelabettersensorconfiguration wouldhaveusedtheinfraredemitter/detector pairthatwas direct,butnotreflective. (They're positioned inaU-shape). Thedevicesenses whenthebeamisblocked andwhenitisnot.Although wehavenoexperimental datatobackthisup,itlookstousthatthis configuration wouldprovetobemoreaccurate andmorereliable. (Youcoulddramatically increase the sensitivity ofthesensor, making ambient lightandtemperature effectslesssignificant.) Apotentiometer mayalsohavebeenworthinvestigating, although reliability concerns frightened usaway.Lesson learned: Therearemanywaystosenseposition -talktootherengineers andlistentotheirpastexperiences with suchdevices. Conclusion We'dliketotakeamoment topointoutthatthisexperience innowaydiminished ourbeliefthattheSMA pinpuller istheappropriate devicetohandlethefailsafe function ofthedesign. Alotoftheproblems we hadcameasadirectresultofhuman error,someofwhichanimproved designcouldhavecompensated for.Otherareascouldnothavebeencompensated forinthedesignwhilestillmaintaining highreliability, lowcomplexity, andlowmass.Asmechanism engineers wehavetoacceptsomeoftheriskleviedonus bytheotherdisciplines ontheteam. Buttoreviewsomeareasthatwouldhavehelpedthedesign: 1)Neverdeliverhardware withpigtails -alwaysincorporate yourownconnector 2)Ensure thattheconnector youplaceonyourmechanism isdifferent fromthosesurrounding it 3)Workwithyourvendors tomakesureallaspects oftheirhardware isconsistent withthehigh standards youhavesetforyourownwork 4)Besuretoincorporate amicroswitch toshutoffanSMAdeviceuponappropriate displacement to ensureoverheating oftheSMAdoesnotoccur. Note: Thisworkwasperformed attheJetPropulsion Laboratory, California Institute ofTechnology, undera contract withtheNational Aeronautics andSpace Administration. Reference hereintoanyspecific commercial product, process orservice bytradename,trademark, manufacturer, orotherwise doesnot constitute orimplyitsendorsement bytheUnitedStatesGovernment ortheJetPropulsion Laboratory. 184
ARobotic Rover-Based DeepDrillerforMarsExploration T.Ylikorpi, G.Visentin ,andJ.Suomela Abstract VTTAutomation hasdeveloped anadvanced rover-based mobiledrillingdeviceforplanetary exploration. ThemobileRobotic Sampling System hasbeendesigned toperform deep(upto2meters) soilsampling onthesurface ofMarsorotherplanetary objects. Duetothecomplexity ofthetask,verystrictmassand volume limitations, andtheneedforcomplete automation ofallitsoperations, thesystem demands avery ambitious mechatronic design. Inthispaper,thedesignofthesystem isdescribed aswellasthefirst functional prototype tobemanufactured andnowundertesting. Thisworkisbeingperformed under European SpaceAgency funding bySpaceSystems Finland Ltd.astheprimecontractor, together with theTechnical Research CenterofFinland (VTT,Finland) (thedrillsystem) andHelsinki University of Technology (therovingsystemanddrillelectronics). Introduction Inthepastfewyearstheworldhaswitnessed thediscovery oflifeformsthriving inextreme environments suchasrocksseveral kilometers underground orunderwater thermal ventswheretemperatures exceed +100degrees Celsius. Theseenvironments werepreviously considered tobetoohostiletosustain any formoflife.Oneofthepossible implications ofthisunexpected proliferation andsurvivability oflifeforms isthatsomesortoflifecouldhavepossibly alsoevolved onotherplanets andmoonslikeMarsorEuropa. Inordertodevelop instruments forsearching foranysignsofsuchextraterrestrial life,theEuropean SpaceAgency hasfunded atechnology research contract called"MicroRobots forScientific Applications 2".Underthiscontract, aRobotic Sampling System (RSS)consisting ofanautomated drillingdeviceand atracked rovingvehicle hasbeendesigned andconstructed. TheRSSconsists ofthefollowing components: 1)AMobileDrillingPlatform thatisbasically asmall(10kg)tracked roverwhosefunction is tohousethedrilling andsampling subsystem andtransport itbetween thelanderandthesample acquisition locations. 2)ADrilling andSampling Subsystem (DSS)toperform theactualdrilling and sampling. 3)ADocking andSample Delivery PortonthelanderwheretheRSScandeliverthecollected samples forfurtherprocessing. Figure1illustrates themission scenario. "_LANDER came LANDER i"-,.f3: -......:C _'-'tether roverwithdrillingandsampling subsystem on-board Figure1.Robotic sampling system scenario. Technical Research CenterofFinland, Helsinki, Finland iiEuropean SpaceAgency, Noordwijk, TheNetherlands Helsinki University ofTechnology, Helsinki, Finland Proceedings ofthe35thAerospace Mechanisms Symposium, AmesResearch Center,May9-11,2001 185
Specifications Thesearchforpossible extinctorextantlifeistheprimary goaloftheexobiology investigations during futureMarsmissions. Aslearned fromtheNASAVikingandPathfinder missions totheMoonandMars, sampling ofsurface soilandrockscangainonlylimited scientific information. Anysensible Martian exobiology investigation requires pristine samples thathaveneverbeenexposed tothelethaleffects of Martian surface environment. Twotypesofsamples havethischaracteristic: 1)samples extracted from surface stones/rocks bycoringatadepthofafewcentimeters, 2)deepsoilsamples acquired vertically fromadepthofmorethan1meter. Foranextensive search forlife,aRobotic Sampling System tobeusedaspartofanexobiology investigation facilityhastoaccommodate thefollowing listofoperational requirements, assetatthe beginning oftheproject: 1.Drillatdepthsranging from0to2meters intoregolith with5mmdepthaccuracy 2.Drillupto2centimeters intosurface rocks/stones 3.Drillintonon-homogeneous material ofdensity andhardness ranging fromloosesandtohardrock 4.Drillatcommanded elevation anglesfrom0°to90°(drillintosurface rocksordirectly intotheground) 5.Drillwithindependent rotation andthrustactions 6.Allowcontrolofdrilldepth(0-2m),rotation speed(0-30RPM)andthrustforce(0-30N) 7.Acquire cylindrical samples (radius 5mmandheight2cm)ofnon-homogeneous material ofdensity andhardness ranging fromloosesandtohardrock 8.Ensure thatthesampled material belongs tothespecific depthofsampling (i.e.,donotcarrydown material fromupperlayers) 9.Preserve themorphology ofthesample (i.e.,donotscramble, compress orstretchit) 10.Preserve thepurityofthesample (i.e.,donotmixitwithothermaterial) 11.Allowacquisition andstorage ofatleast10samples pertrip 12.Carryout3tripsatminimum 13.SizeofDSSisrestricted involume of110x110x350mm 14.MassofDSSisrestricted to5kg. Concept Lay-out Theroboticsampling system consists ofatracked rovingvehicle (110-mm tall,400-mm wide,400-mm longandweighs 10kg)andadrillingsystem (110mmx110mmwide,350-mm longandweighs 4kg) (Figure 2). Drillingandsampling system shouldreachadepthofatleast2m.Itisobvious thatrovermobility would suffergreatlyfromanydrillpartslongerthan0.5mnomatterhowtheyarecarried; vertically, horizontally, orperhaps dragged behind therover.Therefore thedrillstringmustbeassembled ontheroverfrom shorter sections thatarestoredinsidethedrillingsystem. Sinceatotalof30samples areexpected, several holesmustbedrilled.Therefore, thedrillstringmustbereused fromholetoholeandthedrillstringsections shallbeassembled, disassembled andreused ontheroverinanautomatic way.The extendable DSSdrillstringisassembled fromupto10separate pipesinasimilarmanner thatisusedon terrestrial automatic rockdrillingmachinery. The10drillpipesarestoredinarotating pipecarousel, and11drilltoolsarestoredinanother carousel. Linearslidesandball-screw thatgivedrilling thrustandguidance foramoving rotation actuator are located insidethepipecarousel, whichsaveslotsofvolume andgivestheDSSitscompact appearance. Another visiblefeature isaclamping system thatisusedforholding thedrillstringduringaddition or removal ofadrillpipe. 186
Figure2.RSSindrilling position. TheRovin,qVehicle Therovingvehicle procured byHelsinki University ofTechnology; Automation Technology Laboratory, is atracked tethered vehicle, serving asaplatform fortheDSS.Itsfunction istoenabletheDSStosample atdesired locations andtodeliverthesesamples backtothelander.Duringitsmission, therovermakes multiple tripsbetween thelanderandthevarious sampling locations. Theroveriscommanded and supplied withpowerfromthelanderviaatether.Aspecial feature ofthetethersystem isthatitcanbe rewound. Whenreturning tothelander, theroverfollows thetetherleftbehindearlierandwindsitbackto thereelaftercleaning excess dustfromit.Thisway,thelengthofthetetherstoreddoesnotlimitoverall travellengthoftherover,andadanger ofdamaging thetetherbyover-riding itisavoided. Therotating axisofapayload cabholding theDSSallowsdrilling/sampling atanglesranging fromthevertical tothe horizontal. Moreover theliftingbridgeallowsadjustment oftherover's ground clearance. Thisfeature significantly improves therovercross-country ability. Operation Drilloperation issimilartothatforconventional automated drillingmachines usinganextendable drill string.Twoindependent actuators, oneforrotation (0-30rpm,1N-m)andoneforthrust(0-100 N) perform thedrilling. Drillingandsampling procedure consistofthefollowing actions: 1.Selecting thedrillheadfromstorage, 2.Assembling thedrillstringfromsections, 3.Drillingtothedesired depth(inthesoil,orinasurface rock), 4.Acquiring thesample insidethedrillhead, 5.Elevating anddisassembling thedrillstring,and 6.Storing thedrillhead-withthesample- inthesample storage. Therotation actuator -orspindle- ismounted onasledgemoving inandoutalonglinearguidespropelled bythethrustactuator andballnutandscrew.Thespindle isequipped withatrihedron coupling, similarto onesusedforindustrial robots,andwiththenecessary electrical feed-through. Firstthespindle isconnected toonedrillpipeonthepipecarousel, afterwhichatoolfromatoolcarousel isconnected tothelowerendofthepipe.Thendrilling, whichcontinues forthelengthofthepipe,is 187
started.Asthespindlereachesthelowerlimitofitstravel,aclampingsystemcrabsonthepipeandthe spindleisseparatedfromthedrillstring.Astheclampingsystemholdsthedrillstringsteady,thespindle iselevatedbacktotheupperendofthelinearfeedandanewpipeisselectedfromthepipecarousel. Afterthespindleisconnectedtothenewpipethatisfurtherconnected tothedrillstringheldbythe clampingsystem,theclampcanbeopenedanddrillingcanbecontinuedforananotherlengthofthe pipe.Theprocedureisrepeateduntilthedesireddrillingdepthisreached.Retractionofthetooland storingthepipesinthepipecarouselisasequenceoppositetotheassemblyanddrilling. Toolbitdesignissuchthatasthetoolpenetrates throughterrain,soilcanflowthroughit,enteringfrom thelowerendandexitingfromholesintheupperendofthetool.Thisishowthetoolalwaysholdsa samplerepresenting thecurrentdepthinterrain.Uponretrievalofthetool,internalwedgesorflapsinside thetoolholdthesampleandpreventitfromfallingoutofthetool. TheRSSdoesnotcontainanymeansforanchoringtopreventrotationormovingofthesystemduring drillingoperations. Initialrequirements, andalsoselectionofthemotorsandhardwaredesign,limitthe drillthrustto30Nandtorqueto1Norn.Simulatedtestsusingoff-loadingmethodsindicatethattheweight oftheRSSonMarswouldholditstillonsandysurfaceduringdrilling,butforexample,ontheMoon's surfaceadditionalholdingmethodswouldbeneeded. Passive andactiveoperations Duringsystem design, atrade-off between passive andactiveoperations hadtobemadeseveral times. Active operations areoperated withactuators, likemotors andsolenoids, andthusprovide high controllability andflexibility oftheseactions. Passive operations, however, relyongeometry andmovement ofotherpartsofthesystem toprovide the desired action.Passive operations donotneedseparate actuators oranysortofpowerorinformation transmission, andsotheyhavelesseffectonvolume, massandcontrol needs. Passive operations can notbere-programmed though, andtheyproduce ariskincasesomething should gowrong, incaseof jamming ofmovement, forexample. SincetheDSSalready hasmanydegrees offreedom andpowerfeedtomotors andactuators appeared quitechallenging already inthebeginning, itwasdecided toutilizepassive operations asmuchas possible. Activeoperations wereselected whereoperation wasrequired independent fromcurrent operational stateofdrillingsystem. Activeoperations: Carousel rotation Spindle rotation Drillfeed Spindle locking solenoid ClampersTwoindependent carousels. Anyofthetoolsorpipescanbeselected. Independent drillrotation. Independent drillthrust. Thespindle mustbeconnected toandseparated fromthedrillstringin thelowerendandintheupperendoftravel.Inthecaseofstring emergency release, thespindle mustbereleased alsointhemiddleof travel. Theclampers mustbeabletooperate together withthelocking solenoid, i.e.,anytime inthedrillingphase. 188
Passiveoperations: Connection happensbypushingthecouplingstogether,andis'heldby Connection betweenthe pipesandbetweenapipe andthespindle Separation ofapipefromthe spindleattheupperend. Toollockinginsidetool carousel Corecuttingandsample holding.thespringforceofalockingring.Separationforce(pull)ofcouplingsis roughlythreetimeslargerthannominaldrillingthrust.Itwasfoundvery difficulttouseanykindofanactuatortorealizeanactivecoupling system.Alsodeliveringexternalpowertothecouplingforactive operations appearedverychallenging. Thepassive solution selected doesnotappear veryrepeatable andrequires re-work oralternative solutions. Asthespindle withapipe(thelocking solenoid opened) reaches the upperlimitoftravel,mechanical forksseparate thepipefromthe spindle andleavethepipeinthepipecarousel. Solution issimpleand reliable. Toolsarelocked insidethetoolcarousel withasortofbayonet. Locking inhappens byrotating andpushing thetoolpastflexible spring bladesthatsnapoverashoulder formed bycuttingbitsofthetool.The lockisreleased byrotating thetoolsothatduetogeometry theblade becomes liftedabovethecuttingbitsandthetoolcanberemoved from thecarousel. Locking system isfunctional butrequires sophisticated controlofspindle rotation andaxialfeeddurin9procedure. Although pipeconnections provide apossibility torouteelectrical energytotoolbits,apassive operation method wasselected. Thecore iscutfromthebasematerial bycombined rotation andpush/pull ofthe tool.Corecutteroperates inasimilarmanner asthecorecuttersfor conventional coreddlls. Sample stora.qe anddelivery Thetoolbitisdesigned suchthatasthetoolpenetrates through terrain, soilcanflowthrough it,entering fromlowerendandexitingfromholesintheupperendofthetool.Uponretrieval ofthetool,internal wedges orflapsinsidethetoolholdthesample andprevent itfromfallingoutofthetool.Thusthe samples arecollected insidethecoringtool.Afterasample iscaptured insidethetool,thestringis retracted fromtheborehole. Thecoringtoolwherethesample isstoredistransferred tothetoolcarousel intheendofadrillpipe. Thesamples aretransferred fromthecarousel tothelanderwiththeaidofthedrillstringbyconnecting a pipetothespindle; andtothetooltobetransferred totheendofthepipe.TheDSSisthenaligned towards thesample receival port(SRP)ofthelanderandthestringisextended toinsertthetoolintothe SRPoIfthedistance totheSRPexceeds thereachofasinglepipe,connecting morepipestoitwiththe aidofthestringholding devicecanextendthestringfarther. Mechanical desi.qn Spindle andcouplings: Thespindle givesthedrillstringtheneeded drillingrotation, andprovides anelectrical feed-through for spindle locking system andactivedrilltools.Coupling ofthespindle, thatconnects todrillpipes,issimilar torobotic couplings withround-edged trihedron design. Thisgeometry fluently allowspassive coupling of mating partsandhasanabilitytotransfer torquetoo.Electrical connections foractivetoolsarelocated concentric inthemiddleofthepipeconeusingacoaxialplug,seeFigures 3and4. 189
Gearpro¢cCltn Spindk' gear Gent Support Bcanng Sol_l,,,,d bous,_ _l_dg¢ Bca,mg Silpringassschl_. _,edgeIn1em_cd_lc gCal_ p,,,,_l gear R¢lainer d,sk Ihdlnhdc_ Spindle cone hlsulator Coaxial plug Locking nng Figure3.DSSandanexploded viewofthespindle. Securing wedge Spindle Cone Insulation Coaxial plug Locking ring Pipeuppercone Coaxial plug {nsula'_ion Pipetube Figure4.Design ofthecoupling. Thecoupling islockedwithasplitring,oraC-ring,onthespindle part(male), thefemale coupling onthe pipeupperendshasamating groove forthering.Shapeofthegroove ismadenon-symmetric with different conical anglessuchthatcoupling bypushing happens easily,butde-coupling bypullingrequires aforcecloseto100N,whichisclosetothelineardrivecapacity. Itwassoonlearned thattheC-rings needed tohaveaspecial designtooperate withthedesired forces. Several different designs were incorporated andtested.ThegroovefortheC-ringhasangledsurfaces sothattheslightly contracted ring causes somepre-load forthecoupling. 190