ai-aerospace/ams_data_full_2000-2020 huggingface dataset:
Fault Tolerant ,_la_ne¢ic' _ear_ng ,_(odnl Controller _'iLh Safe Gain andpower_f_.'_itch Feature_ (II-i0-99) Figure1Fault-Tolerant Magnetic Suspension TestRig.DI]rFERENOED PROBE pO_ITIr)N i_rPt]l_ ] "' Figure4:Controller blockdiagram fortheFaultTolerant Magnetic Suspension TestRig. Figure2:Associated hardware forFaultTolerant Magnetic Bearing Suspension TestRig.Figure5:Control cockpitwindow thatadjusts system parameter valuesandsimulates multiple component failures. Figure3:Fault-tolerant control panelthat simulates coilor/andamplifier failures byusing manually controlled mechanical switches.Figure6:Current inputstocompensate thefirst polefailedoperation at0rpm. 131
Figure7:Currentinputstocompensate the consecutive 1-4-6thpolesfailedoperation at0 rpm.Figure10:Currentinputstocompensate the consecutive 5-6-7-8-2-4 thpolesfailedoperation atthemaximum allowable speedof20,000rpm. Onlytwoactivecoilsof1and3. Figure8:Currentinputstocompensate the consecutive 2-3-5-7thpolesfailedoperation at themaximum allowable speedof20,000rpm.Figure11:Transient sensorplotofthefailed situation ofFigure13.The5-6-7-8 thpolesprefailed,followed bythe2-4thpolesfailedcase. Onlytwoactivecoilsof1and3at20,000rpm. Figure9:Currentinputstocompensate the consecutive 2-3-5-7-6-8 thpolesfailedoperation atthemaximum allowable speedof20,000rpm. Onlytwoactivecoilsof1and4. 132
Figure1.Spalled GearPinion(AreaC) Process Background Inordertounderstand thereasons fortheproblems encountered inthisprocess, adescription ofLSBNis presented. LSBNusesacombination ofpotassium andsodium cyanate salts(KCNO andNaCNO) ina moltenstate,typically at580°C(1075°F). Thesesaltsreactwiththeironatthesteelsurface andrelease carbonandnitrogen asfollows: 8CNO-=2CO3-2+4CN-+CO2+[C]Fe-I-4[N]Fe (1) Thedesired product inthisreaction isthe4[N]Fe,orepsilon ironnitride.Thiscompound improves thewear resistance ofsteels. Thereaction andsubsequent diffusion ofthecarbonandnitrogen isrepresented schematically inFigure2. OntheleftistheKCNOsalt,whichreleases theCandNatthesurfacetoproduce thecompounds shownin Equation 1.Thezonewherereaction occursiscalledthecompound layer,andistheareawherespalling problems mayoccur.Compound layersrangeinthickness from0.005mmto0.025mm(0.0002 into0.001 in),depending onresidence time,bathtemperature, andthealloycomposition ofthetreatedsteel.Unreacted nitrogen willdiffusebelowthecompound layer,producing asolution ofnitrogen iniron.Thislayer,calledthe diffusion zone,canimpartimproved fatiguestrength ontheprocessed partifitisagedat300°C(570°F) in ordertoprecipitate Fe4N_.Thislayerismuchdeeperthanthecompound layer,measuring upto1.02mm (0.040in)2.Figure3showsatypicallowcarbonsteelafterLSBNtreatment, showing therelative thickness of thecompound zoneandthediffusion zone,aswellastheironnitddeneedles formed inthediffusion zone afteraging. 1Wensing, Donald, etal,"LiquidNitriding," ASMCommittee onLiquidCarburizing, p.254. 2Wensing, p.254. 134
Figure2.Schematic oftheNitrocarburizing Process 3 Compound Figure3.Nitrocarburized LowCarbon Steel4 Enqineerin.q Properties ofNitrocarburized Steels Theenhanced engineering properties ofsteelsprocessed wJthLSBNinvolve improved wearresistance, reduced coefficient offriction, andimproved fatiguestrength. Theimproved wearresistance isprimarily due toincreased surface hardness (640minimum KnoopKHloofor13-8PHsteel).Inaddition, thesurface ofthe compound layerduringprocessing develops microporosities whichactasreservoirs forlubricant 5.These micropores makethesurface idealforholding leadplating, whichhelpimprove wearresistance. Thereduced coefficient offrictionisalsoduetotheincreased surface hardness, andgenerally resultsinacoefficient of 3Easterday, JamesR.,"SaltBathFerriticNitrocarburizing," KoleneCorporation Technology Update (1996), 4PE2sterday, p.3. SEasterday, p.3. 135
Anotherproblemspecifictothispinionwasthesizeoftheparts.Mostcommercial LSBNprocessors use tanksapproximately 1-mlongby1-mwideby3-mdeep.Iflargeloadsofpartsareprocessed beforethe smallpinions, carbonate precipitation (Equation 1)causes sludgetodevelop atthebottom ofthetank, resulting inreduced airagitation. Thesmallpinionsplacedinalargetankwithreduced airagitation resulted inpoorsurface contact withthesalts,causing uneven compound layerformation. Therefore, smaller vessels withimproved airagitation willproduce amoreconsistent compound layer. Problem Resolution TheU.S.manufacturer ofthesaltbaths,KoleneCorporation, wascontacted touselaboratory scaleLSBN processing inordertocontroltheaforementioned factorsthatledtothespalling problem. Thefirstpartsrun through thelabusedtheprevious LSBNprocessor's parameters. Thepinions showed goldcolored areas wherethesaltbathsolution didnotpenetrate, possibly duetoinadequate removal ofsurface oxides(usually chromium oxide)priortoLSBN.Thisgroupwasimmersed inthesaltbathforanadditional 10minutes, and thepinions showed complete blackening ofthesurface. However, thecompound layerrangedinthickness fromapproximately 0.01mmto0.02mm(0.0005 inchto0.001inch),arangethatKolene agreedwastoo deepforpinionsofthisconfiguration. Asecond groupofpinions wasfirstprecleaned for10minutes inanultrasonic bathcontaining aproprietary alkaline cleaner heatedto70°C(160°F) inordertoremove surface scale.Thepartswerethenrinsedwith waterandpreheated. Thenextoperation, saltbathimmersion, iscriticaltocontrolcompound layerdepth, andthelabdetermined thata25minute+1minuteexposure at550°C+10°C(1020°F +20°F)wassufficient toproduce acompound layerof0.0038mmto0.0127mm(0.00015 into0.0005in).Table1compares the parameters fromthefirstLSBNprocessor andKoleneCorporation's laboratory. Whencompared stepby step,theredoesnotappear tobeasignificant difference, buttakentogether therewasagreatimprovement fromthe50%yieldseenpreviously. Whenthesecontrols wereimplemented onsubsequent production runs, 95%ofthepartsshowed nosignofspalling, andhavebeenusedsuccessfully onflightqualified motors. The improved product yieldresulted inachange inourcustomer's LSBNprocurement specification toreflect theseprocess changes, Table1 Comparison ofCommercial ShopLSBNandKolene LabLSBNParameters for19Tooth,4.7-mm (0.185in)Diameter, 13-8PHPinion Process Step Pre-Clean Pre-Heat SaltBathNitriding Quench Bath AirCool WaterRinse Secondary WaterRinse {Ultrasonic) Compound LayerCrossSection AnalysisShopLSBN WateratRoomTemperature 370°Cto400°C(700°Fto 750°F), 30minutes 560°C+5oc (1040°F +10°F), 30minutes +1minute Airagitation wasnotconsistent fromlottolot. 425°Cto440°C (800°Fto825°F) 10minutes Asrequired iUntilpartsarecool totouch) Asrequired (Untilmostofthe saltsareremoved) Asrequired (Untilallvisiblesalt isremoved) 0.0127mmto0.025mm(0.0005 into0.001in)casedepth,640 HK1o0atsurfaceKolene Lab Alkaline, UItrasonic, 160°F,10 Minutes 370°Cto400°C(700°Fto 750°F), 30minutes 550°C+10oc (1020°F +20°F) 25minutes +1minute Vigorous airagitation 400°Cto425°C(750°F-800°F) 10minutes Asrequired 10minutes Notused 0.0038mmto0.0127mm (0.00015 into0.0005in)case depth,640HK100atsurface 137
Conclusions Theprocess parameters showninTable1areonlyapplicable forthisparticular part;however, somegeneral guidelines forsuccessful yieldswhenusingPHstainless steelscanbesummarized asfollows: .Paycloseattention tothepartgeometry. Iftherearefinethreads, finegearteeth,orothersmalldetails present onthesurface tobenitrided, specify acasedepthof0.013mm(0.0005 inch)maximum. The temperature andresidence timewillbedetermined bytestingsample piecesuntilthedesired casedepthis achieved. .MakesuretheLSBNprocessor thoroughly cleansthepartsbeforenitriding, preferably byusingaheated alkaline ultrasonic bath.Anyscaleonthesurface willprevent uniform compound layerformation. •Makesuretheprocessor maintains vigorous airagitation inthesaltbathtankwhenprocessing partswith finesurface geometries. References , 2. 1996.Wensing, Donald, etal."LiquidNitriding." ASMHandbook Volume 04:HeatTreating (1991). Easterday, JamesR."SaltBathFerriticNitrocarbudzing." KoleneCorporation Technology Update, 138
forged,andhotrolledtoproduce bar.Samples werecutandevaluated forheattreatresponse, retained austenite content, corrosion resistance, andwearresistance assummarized inthefollowing sections. HeatTreatment Response Heattreatment response wasinitiallyevaluated byaustenitizing at1121°C (2050°F), 1149°C (2100°F), and1177°C (2150°F), oilquenching, andthendouble tempering between 260°C (500°F) and593°C (1100°F). Asecond heattreatment response studywasperformed usingthesameaustenitizing, tempering, and quenching procedures, butincorporating refrigeration at-75°C(-103°F) foronehourbetween tempers. Theresultsofbothheattreatment surveys arepresented inFigure1. 68 66 64 ,...62 O Z60 c-58 "o m 56•m_,Austenitized at1121°C __Austenitized at1149°C -Austenitized at1177°C •1121°C,refrigerated64 B1149°C,refrigerated 52•1177°C,refrigerated 50.................................... 250 300 350 400 450 500 550 60O Tempering Temperature (°C)650 Figure1.Tempering CurveforCPM®VIMCRU®60'M(twohourdouble-temper) Retained Austenite Content Results ofx-raydiffraction retained austenite (RA)determinations arepresented inTable2.CPM®VIM CRU®60TMcontained approximately 16%IRAwhenoilquenched from1177°C (2150°F) and5%RAwhen quenched from1149°C (2100°F). Tempering at510°C(950°F) afteroilquenching fromeithertemperature eliminated allretained austenite. Tempering at260°C(500°F) alsoeliminated mostoralloftheretained austenite, defying theconventional wisdom thataustenite tomartensite transformations willnotoccurat lowtemperatures (<315°C). Theresultsforrefrigeration treatments forCPM®VIMCRU®60TMweremixed.Cooling to-75°C(-103°F) immediately aftertheoilquench significantly eliminated orreduced theas-quenched retained austenite contents tobelow2%RA(thedetection limitofthex-raydiffractometer) forboth1149°C (2100°F) and 1177°C (2150°F) austenitizing. However, applying therefrigeration treatment between adoubletemper at only260°C(500°F) resulted in3%RAfor1149°C (2100°F) austenitizing and13%IRAfor1177°C 141
(2150°F) austenitizing -i.e.relatively littlechange fromtheas-quenched numbers. Thisimplies thatsome stabilization oftheaustenite content hadoccurred. Table 2.Retained Austenite inCPM®VIMCRU®60TM Austenitizing Temperature -) HeatTreatment As-Austenitized OQ 5% OQ+refrigeration beforetempers OQ+refrigeration between tempers<2%1149°C 12100°F) Tempered 2+2 hours 260°C 510°C <2% <2% <2% --- 3% ---1177°C (2150°F I Tempered 2+2 hours As-Austenitized 260°C 510°C 16% --- <2% <2% <2% --- --- 13% --- Wear Resistance Twotypes ofweartestswere performed onCPM®VIMCRU®60TM: crossed cylinder andpinabrasion (Table 3).Other materials evaluated were440C, CPM®VIMCRU®80TM,and98VN084. These same testshavebeen usedinthepasttoevaluate wear resistant materials [9].Thecrossed cylinder weartest (metal-to-metal) wasperformed withstationary samples oriented perpendicular toarotating tungsten carbide cylinder, inamanner similar toASTM G83.Ahigher wearnumber isbetter inthisparticular test. Thewear resistance ofCPM®VIMCRU®60TMinthistestissignificantly greater thantothatof440C, especially when CPM®VIMCRU®60TMismultiple tempered at538°C. Thepinabrasion weartestconsists ofrotating cylindrical specimen pressed atafixed loadagainst an abrasive cloth. Thetestapparatus operates insuchawaythatthesample isexposed tofresh clothfor theentire duration ofthetest.Alower weight lossvalue isbetter. Again VIMCRU®60TMexhibited wear resistance significantly greater thanthatof440C. Corrosion Testinq Corrosion testing results fromVIMCRU®60TMwerecompared tothose of440C, CPM®VIMCRU®80TM, and98VN084. Results maybefound inTable 3.When double tempered at260°C (500°F), CPM®VIM CRU®60TM,CPM®VIMCRU®80TM,and98VN084 allexhibit corrosion resistance characteristics atleast comparable tothatof440C hardened from1040°C (1904°F) anddouble tempered at200°C (392°F). Tempering CPM®VIMCRU®60TMor98VN084 at538°C (1000°F) reduces thecorrosion resistance compared to260°C (500°F) tempering, butwewould expect similar orperhaps somewhat worse results for440C using hightemperature tempering. Table 3.Wear andCorrosion Resistance ofCorrosion Resistant ToolSteels WearTestResults Corrosion TestResults Material 440C CPM_VIM CRU_80TM CPM_VIM CRU_80TM CPM_VIM CRU_60TM CPM®VIM CRU_60TMAustenitizing Temperature (°C) 1040Tempering Temperature (°C) 200Hardness (HRc) 57.5Crossed Cylinder Wear Resistance* (xl0Zkg/mm 2) 4PinAbrasion Wear Resistance Weight Loss**(mg) 66Dilute AquaRegia 24°C-3 hr. (mm/yr.)+ 109.010% AceticAcid Boiling -24 hrs. {mm/_'r.l++ 29.0 1121 260 58 9.5 57.9 117.0 17.0 1177 260 58.5 11.9 50.5 102.0 g.0 1149 260 61 38.6 30.5 110.9 57,3 1149 538 62.5 50.9 27 355.1 141.4 98VN084 1149 260 60.5 41.8 30 70.1 15.2 98VN084 1149 538 60.5 40.4 29 309.1 121.0 *higher number isbetter **lower number isbetter +Specimens exposed for3hoursina24°Caqueous solution containing 5vol.%HNO3and1vol.%HCI ++Specimens exposed for24hoursinaboilingaqueous solution containing 10vol.%aceticacid. 142
forcewhenthejointopensabouttheneutralaxis.Alltheboltsinthejointwillexperience tensileforce whenthejointopensabouttheedgeofthestage. Tensileforceshavebeencalculatedforbothpossiblewaysofjointopening,andthereleaseboltis designedforthehighertensileforceoutofthese.Forthejointopeningabouttheneutralaxisasshownin Figure2(a),themaximumforcewillbeinthebolt,whichisfarthestfromaxisofopeninganditisgivenby F1:(BM.PCD•Ab)I(2"Isy) where PCD=pitchcirclediameter Ab=boltcross-section area Isy=Ib+Ab7-x_2 Ib=moment ofinertiaofthebolt x,=distance fromneutralaxis Forthejointopening abouttheedgeofthestage,itisassumed thatthetension inboltdeveloped dueto thebending moment isproportional tothedistance oftheboltfromtheedgeofthesection. Assuming n (evennumber) number ofboltsarenecessary towithstand loads,alltheboltsofthejointwillbeintension andthejointwilltrytoopenabouttheN-AaxisasshowninFigure2(b).Maximum tensileforcewillbein theboltthatisfarthest fromaxisofopening andgivenby F.=8°BM/3°n"PCD Separation Dynamics Thepyrocartridge generates high-pressure gases(orderof80MPa)inthefreevolume between the pistonandpyrocartridge. Gaspressure actsonthepyrocartridge andpiston.Sincethepyrocartridge is mounted onthearrestor, thearrestor movesandmakesthecolletsfree.Oncethecolletsarefree,they moveradially outwards withtheforcetransferred bytherelease boltoncollets, andatthesametimethe pistonmovesaheadandpushes theboltout.Theforceactingonthepistonissufficient tomovethebolt against friction forces. Thestrokelengthofthepistonissufficient topushtheboltoutofthepyrobolt casing. Sincethearrestor andrelease boltmoveinopposite directions, thenetrecoilforceonthe pyrobolt mounting islessandsorecoilshockisless.Majorshockinpyrodevices isduetorecoilforces, whichisverylowinpyrobolt. Sotheseparation shockisless.Thepyrobolt isassembled withtwostages asshowninFigure3.Thepyrobolt afterfiringisshowninFigure4.Aguideisprovided allalongthe circumference asshowninFigure4toavoidlateralmovement ofthespentstagejustafterthepyrobolts arefired.Thespentstagecanseparate whenitrotates aboutitsedgeasshowninFigure5.Thebolt headmayinterfere withtheon-going stageasshowninFigure5.Thismayleadtoadisturbed stage separation. Thiscanbeavoided iftheguidelengthissufficient andlocalflangethickness ofon-going stageisminimum. Thetapered holeintheflangewillalsoallowtheboltheadtocomeoutwithout interfering asshowninFigure5. Separation Shock Separation shockismeasured byplacing accelerometers atdifferent locations onthespentstageandthe on-going stage.Bruel&Kjaermodel8309accelerometers areused.Threesensors 1,2&3areplacedto measure axialshocks and4,5,&6areplacedtomeasure radialshocks. Theshocklevelsatthe locations aregiveninTable1. Table1:Separation Location 1 2 3 4 5 6ShockLevels atDifferent Locations ShockLevel 600g,for20ms 500g,for20ms 2009,for10ms 100g,for10ms 500g,for20ms 5009,for20ms 146
Conclusion Stageseparation shockinpyrobolt-actuated stageseparation isverylowandsothisstageseparation mechanism isveryusefulforapplications wheretheseparation planeisclosetoshocksensitive packages/passengers. Theassembly anddisassembly ofstagesareeasyandsafe.Maintenance ofthe separation system iseasyandsafe.Thefunctionality ofapyrobolt canbeconfirmed bypneumatic pressure beforeitisassembled totheflyingvehicle. References 1.S.VaraPrasad Rao,Deepak Agrawal. "Pyrobolt forLowShockStageSeparation Mechanism". National Seminar onAerospace &Related Mechanisms, Paper13. 2.NeilButterfield. "Pyrotechnic Release Devices". SpaceVehicle Mechanisms Elements ofSuccessful DesigneditedbyPeterL.Conley. 3.KarlO.Brauer. "Handbook ofPyrotechnics" p. Before operation Afteroperation Figure 1.Pyrobolt beforeoperation andafteroperation I---t - t---I ......... i (a).Jointopening aboutNeutral axis (b).Jointopening aboutedge Figure2.(a),(b):Possible waysofjointopening 147
•--/V/ // Design ofaHighResolution Hexapod Positioning Mechanism JamieBritt* Abstract Thispaperdescribes thedevelopment ofahighresolution, six-degree offreedom positioning mechanism. Thismechanism, basedontheStewart platform concept, wasdesigned forusewiththeDevelopmental Comparative ActiveOpticsTelescope Testbed (DCATT), aground-based technology testbed fortheNext Generation SpaceTelescope (NGST). Themechanism provides activecontroltotheDCATT telescope's segmented primary mirror.Emphasis isondesigndecisions andtechnical challenges. Significant issues include undesirable motion properties ofPZT-inchworm actuators, testingdifficulties, dimensional stability anduseofadvanced composite materials. Supporting testdatafromprototype mechanisms ispresented. Introduction Large,active-optics systems forspacearepushing thelimitsof positioning mechanism design. Activeopticsmechanisms require increased motion resolution andposition stability, ofteninmultiple degrees offreedom. TheDCATT telescope isaground-based example ofthistypeofsystem. Figure1showsamodelofthe DCATT testbed. Thevertical structure isDCATT's Cassegrain telescope, standing 4.6m(15feet)tall.Figure2showsDCATT's one-meter-diameter primary mirror, which consists ofseven hexagonal, aluminum segments, Aspartofthetestbed's experimental plan,thesesegments mustbeactuated insixdegreesof-freedom (6-DoF) withnanometer andarc-second resolution over arange ofmillimeters anddegrees. Onceinposition, the mechanisms mustholdposition foroneormorehours. TheresultistheDCATT hexapod positioning mechanism. Basedon theStewart platform concept, theDCATT hexapod provides 6DoFmotion usingatruss-like arrangement oflinearactuators. Figure 1.DCATT Testbed Model Thisarrangement isbothcompact andrigid.Commercially available, piezo-electric, PZT-inchworm actuators provide thehexapod's high-resolution motion. Materials withlowandnegative coefficients ofthermal expansion (CTE)areusedinthelegstoprovide maximum dimensional stability. Anumber ofobstacles hadtobeovercome duringdevelopment of themechanism. Thefirstchallenge involved motion testsofthe selected actuators, whichrevealed undesirable motion properties. Developing ahigh-resolution, 6-DoFmotion testwasthenext challenge. Thistestbrought tolightproblems withthedimensional stability ofboththemechanism andthetestsetup.Thesewere addressed withnewdesigns incorporating Iow-CTE metals and negative-CTE composites. Alloftheseissues, alongwiththeir solutions willbepresented inthispaper. Figure2.DCATT Primary Mirror (shown inpolishing fixture)Priortointegration andtesting ofthefinalhexapod design, the DCATT projectwascancelled duetoashiftinfocusoftheNGST project. Thus,finalperformance testing ofthehexapods was neverperformed. •NASAGoddard SpaceFlightCenter, Greenbelt, MD Proceedings ofthe35thAerospace Mechanisms Symposium, AmesResearch Center,May9-11,2001 149
DCATT Hexapod Requirements General Requirements TheDCATT testbed wascreated totestopticalwavefront controlforNGST.Thegoalwastousethese methods toachieve diffraction-limited performance intheDCATT telescope. Thisrequired activecontrol ofthetelescope's segmented primary mirror.TheDCATT hexapod wasdesigned toperform thistask. Thesegments wereconstructed frommachined aluminum withmirrorsurfaces ofpolished-nickel. Each outersegment weighed 2.3kg(5Ib).Thecentersegment weighed 1.4kg(3Ib).Allsevensegments had tobeactuated in6-DoFfrombeneath themirror.Thus,eachmechanism hadtosupport andactuate the weightofasegment• Inaddition, lightpassing through centersegment's holecouldnotbeobstructed. Actuation Ran,qeandResolution Table1givestherangeandresolution requirements fortheDCATT hexapod inthreecriticaldegrees of freedom. Tipandtiltarerotations perpendicular totheopticalaxisofthemirror.Pistonislinearmotion parallel totheopticalaxisofthemirror.Although theotherdegrees offreedom whererequired, theydid nothavespecific resolution orrangerequirements attached tothem.Theysimplyhadtobeofthesame orderofmagnitude asthecriticalthree. Table1.Actuation Requirements: Resolution andRange Tip/tiltresolution +/-0.01arc-sec Tip/tiltrange +/-0.5° Pistonresolution +/-0.1I_m Pistonrange +/-0.05mm TheDCATT hexapod's resolution requirement isdrivenbytheneedtoalignthesegments oftheprimary mirror.Therangerequirement isdrivenbytheneedtomisalign thesegments byoptically largevaluesat thestartofanexperiment. Position Stability Aminimum requirement forjittermotion wasnotgivenatthestartofthedesignprocess. Jitterstability wasimplied bya100-Hz minimum-stiffness goalforthehexapod's firstmodeofvibration. Long-term stability wasimplied byarequirement thatthetelescope be"self-compensating" fordimensional changes caused bythermal expansion. Thismandated thatthestructure havethesameCTEas themirrors. Sincethemirrors weremadeofaluminum, thestructure andhexapods weretobealuminum aswell. DCATT Hexapod Concept Figure 3shows acomputer model forthealuminum DCATT hexapod. Eachlegcontains anIW-700 PZTInchworm linearactuator manufactured byBurleigh Instruments 1.Allpartsarealuminum except fortheactuators andthreeflexures ineachleg.Figure4 showsanexploded viewofalegassembly. Theflexures provide the samedegrees offreedom asball-and-socket jointsinanideal Stewart platform, butwithout thefrictional problems ofrealball-andsocketoruniversal joints.Figure3.Hexapod Model Burleigh Instruments, Inc.,Burleigh Park,Fishers, NewYork,14453-0755 150
UpperHousing (Aluminum)_ LowerHousing _ (Aluminum) Clamps _¢_ LowerShaft(Aluminum) (Aluminum)Flex-Pivot - AxialRotation Flexure (Steel) 2-Axis _Bending Flexure (Steel) RodEnd\ (Aluminum) "aUpperShaft (Aluminum)  _.,Burleigh IW-700 Actuator2-Axis Bending Flexure (Steel) Figure4.Exploded ViewofHexapod Leg Table2showsthestatedperformance oftheIW-700 actuators. Table3showsthepredicted performance ofthehexapod compared totherequirements. Thesepredictions werecalculated usingtheIW-700 performance numbers andakinematics modelbasedonthegeometry ofthehexapod. Table2.IW-700 Performance Minimum StepSize: Actuation Rankle:4nm 6ram Table3.Predicted Hexapod Performance Motion Tip/TiltResolution Tip/TiltRange* PistonResolution PistonRange*Requirement +/-0.01 arc-sec +/-0.5deg +/-0.1#m +/-0.05mmPredicted Performance +/-~0.002 arc-sec +/-1.0degw/+/-1.0 mmpiston +/-1.7degw/+/-0.5 mmpiston +/-2.0degmaximum range +/--0.005_Jm +t-0.5mmw/+/-1.7 degrange +/-1.0mmw/+/-1.0 degrange +/-3.4mmmaximum range *NOTE: Maximum ranges foralldegrees offreedom arecoupled. Sample extremes withinthemotion envelope aregiven. PZT-lnchworm Actuator Motion Issues Foragoodportion ofthedesign process, theassumption wasmadethattheIW-700 actuators would movewiththeresolution statedinTable2overtheirentirerangeofmotion. Thiswouldallowthe actuators tobeoperated inanessentially open-loop fashion. Control software woulddetermine howfar eachactuator hadtomovetoposition themirrorsegment andthencommand acertain number of 151