Abstract: Smalltimelocalcontrollability(STLC)andstabilizabilityofthespacecraftattitudeunderactuatedbyreactionwheels(RWs)wereinvestigatedwiththewheelspeedsascontrolinputs.Firstly,withthewheelspeedsbeingtreatedasinputs,theconservationconstraintofthetotalangularmomentumofthespacecraftandRWswasdirectlybroughtintothedynamicsofthesystem.ThennonlinearcontrollabilityandstabilizabilitytheorywereutilizedtoanalyzethecontrolpropertyofthisdynamicswithoneandtwoRWsrespectively.TheresultsshowthattheSTLCofthespacecraftattitudeispossibleonlywhentwononcoaxialRWsareavailable.Simultaneously,thesystemcannotbeasymptoticallystabilizedbyatimeinvariantsmoothfeedback,butitstillcanbeasymptoticallystabilizedatleastbyapiecewisecontinuousfeedback.Accordingly,anonsmoothcontrollawbasedonquaternionwasconstructedtostabilizethespacecraftattitudewithwheelspeedsunderthesaturationlimits,whichnotonlyconfirmsthetheoreticaloutcomesbutalsoispracticallyuseful.

Key words: Reactionwheel, Localcontrollability〓AsymptoticstabilizationUnderactuatedspacecraftReactionwheel, Localcontrollability, Asymptoticstabilization, Underactuatedspacecraft