ZeroDeadband, Multiple StrutSynchronized HingeforDeployable Structures Matthew Botke*, DavidMurphy*, Thomas Murphey*, PeterSorensen** Abstract Manyconfigurations existintheliterature regarding thesynchronization ofhingedelements indeployable structures. Thispaperdetailsthedesignandmanufacturing aspects ofatapedrivemechanism thatuses acentral pulleytodriveoneormorehinged elements orstruts.Themechanism functions asa synchronizer andcanbepowered orunpowered. Anadvantage tothissynchronization approach over othersisitsimplementation ofsimple mechanical itemsinastatically determinant arrangement that facilitates astraightforward analysis approach. Thedesignalsolendsitselftomanufacture, assembly, test aswellaslowcost.Thisdesignapproach possesses wideapplicability toabroadrangeofdeployable structures. Introduction Theneedforanewapproach tomultiple strutsynchronization aroseinthedevelopment ofanovelsolar arraysystem (patent pending). Thearrayisdesigned todeployalargeareaofthinfilmorcrystalline photovoltaic devices (upwards of150m-ormoreperwing).Thedeployment kinematics require hinge elements inthearraytosynchronize eachconnected member. Thearraypowertomassefficiency is designed tobeintherangeof200to250W/kg.Inattempting toachieve thisjumpinmassefficiency from thestateofpractice, themassofthearraystructure mustbehighlyoptimized. Thedesignchallenge isto develop astructure thatisrobust, hasbothhighstowed anddeployed packing factors, isextremely mass efficient andprovides thefunctionality required toreliably deploythearray.Thesubject hingewouldbea repeating element inthearraydesigned toreduceuniquemechanism count.Thedesignprocess forthis hinge,lessons learned sofar,aswellasthecurrent stateofthedesignarepresented hereinorderto illustrate apossible solution toabroadrangeofdeployable structures requiring zero-deadband synchronized andefficient motionoftwoormorestruts. Background Thedeploy sequence ofthemodular arrayisdepicted inFigure1.RefertoFigure2forstructure nomenclature ofabay.Deployment isinitiated byreleasing thetiedown mechanism (notdepicted). The arraystructure andyokearedeployed simultaneously andlatched. Eachcornerhingeelement ornode synchronizes thedeployment angleofeachconnected strut.Theyokeissynchronized similarly. By synchronizing eachstrutatthenodes, eachbayandhencetheentirearraydeployment kinematics are defined. Deploy motiveenergy isinputviamotors atselected nodes.Stepper motorsareusedtocontrol rateandpreclude possible binding modes thatcouldbecaused byunbalanced torques. Un-motorized nodesincorporate helpersprings inordertojustovercome localsources ofparasitic torque. The deployed structure formsanumber oftiledpictureframeelements or'bays'.Considering thekinematics ofasinglebay,thesinglestrutsidesofthebayremainparallel duringdeployment. Lanyards arepaidout duringthestructure deployment between thesesidesandterminate atthestowed photovoltaic blanket packaged against theinboard singlestrutside.Theseblankets remain stowed untilthestructure isfully deployed andlatched uponwhichtimethelanyards arereeledbackintodeploytheblanket. "AEC-Able Engineering, Goleta, CA Kollabra, PaloAlto,CA Proceedings ofthe36thAerospace Mechanisms Symposium, GlennResearch Center,.May15-17,2002 NASA/CPm2002-211506 77