Robust adaptive sliding mode attitude control and vibration damping of flexible spacecraft subject to unknown disturbance and uncertainty

Abstract

This paper is concerned with the development of a control system for rotational manoeuvre and vibration suppression of a flexible spacecraft. The design approach presented here treats the problem of spacecraft attitude control separately from the elastic vibration suppression problem. As a stepping stone, a state feedback sliding mode control command is designed to achieve the reference trajectory tracking control of attitude angle. This is followed by the design of an adaptive sliding mode control law using only output for robust stabilization of spacecraft in the presence of parametric uncertainty and external disturbances. Even if this controller has the ability to reject the disturbance and deal with uncertainty, it excites the elastic modes of flexible appendages. The undesirable vibration is then actively suppressed by applying feedback control voltages to the piezoceramic actuators, in which the modal velocity feedback control method is adopted here for determining the control voltages. The effectiveness of the control schemes in handling external disturbance and uncertainty in the system parameters is also studied. Both analytical and numerical results are presented to show the theoretical and practical merit of this hybrid approach.