ATTITUDE-CONTROL USING GIMBALED THRUSTERS

Spacecraft slewing maneuvers are typically controlled by means of thrusters which are pulsed on and off as required. Unfortunately, as spacecraft become larger and more flexible, these thruster transients are more and more likely to excite undesirable flexible modes. This paper presents a preliminary analysis of a novel slewing technique which is designed to avoid such problems. In this approach, the control thrusters 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 nonlinear, making a stability analysis quite challenging. As the first part of such a study, a characterization of the equilibria of the system is used to obtain acceptable values for the control gains. Lyapunov techniques are then employed to prove global asymptotic stability. Finally, the properties of the controller are illustrated by means of simulation results.