ATTITUDE-CONTROL USING GIMBALED THRUSTERS

Spacecraft slewing maneuvers are typically controlled by means of thru sters which are pulsed on and off as required. Unfortunately, as space craft become larger and more flexible, these thruster transients are m ore and more likely to excite undesirable flexible modes. This paper p resents a preliminary analysis of a novel slewing technique which is d esigned to avoid such problems. In this approach, the control thruster s remain on throughout the maneuver; they are gimbaled according to a feedback scheme based on the instantaneous pointing angle and rate of the spacecraft. The resulting closed-loop dynamics are highly nonlinea r, making a stability analysis quite challenging. As the first part of such a study, a characterization of the equilibria of the system is u sed to obtain acceptable values for the control gains. Lyapunov techni ques are then employed to prove global asymptotic stability. Finally, the properties of the controller are illustrated by means of simulatio n results.