Active vibration suppression in flexible spacecraft attitude maneuver using variable structure control and input shaping technique

A generalized scheme based on the variable structure output feedback control (VSOFC) and input shaping (IS) technique has been proposed for the rotational maneuver and vibration suppression of an orbiting spacecraft with flexible appendages. The proposed control design process is two fold: design of the attitude controller followed by the design of a flexible vibration attenuator. On the basis of VSOFC theory, the attitude controller, using only the attitude and angular rate measurement, consists of linear and discontinuous feedback terms. The linear and discontinuous feedback gains are designed so that the sliding surface exists and is globally reachable. With the presence of this attitude controller, an additional vibration attenuator, using input shaping technique, is designed to eliminate unwanted flexible modes of vibration while achieving the desired closed-loop motion by producing a command profile that only requires information about of the natural frequency and damping of the closed-loop system. The proposed control strategy has been implemented on a flexible spacecraft, which is a hub with a cantilever flexible beam appendage and can undergo a single axis rotation. The results have been proven the potential of this approach to control flexible spacecraft.