Patent ID: 6517029
Filing Date: 2003-02-11
Classification: B64G

Abstract:
A spacecraft attitude control system comprising:at least one reaction wheel responsive to a torque drive signal for torquing said spacecraft; means for generating a desired torque control signal; means for generating an estimate of friction signal for said at least one reaction wheel; means for detecting if stiction of said at least one reaction wheel is present; means for generating a stiction compensated estimate of friction signal responsive to said detecting means detecting the presence of stiction; and means for compensating for friction or stiction of said at least one reaction wheel by selectively correcting said desired torque control signal for friction or stiction errors to generate said torque drive signal, wherein said compensating means selectively utilizes said estimate of friction signal to correct said torque control signal when no stiction is present or said stiction compensated estimate of friction signal to correct said torque control signal when stiction is present.