Disturbance/modal observer based composite controller for rapid vibration suppression using only attitude actuators in flexible spacecrafts

In flexible spacecrafts subject to multiple disturbances, only attitude actuators can be employed to realize rapid vibration suppression as well as high-precision attitude control for system structure simplification. However, most existing methods struggle to simultaneously ensure attitude control performance and vibration suppression performance since the attitude actuators are non-collocated with the flexible appendages. In this paper, a disturbance/modal observer based composite control method is proposed to achieve rapid vibration suppression as well as high-precision attitude control by using only attitude actuators. First, the disturbance/modal observer is designed to accurately estimate the lumped disturbances and separate flexible modals according to the refined classification and modeling of multiple disturbances. Then, a sliding mode controller is designed following the backstepping method with the help of the proposed observer. It can effectively attenuate disturbances and rapidly suppress flexible vibrations through high-precision disturbance feedforward compensation and flexible modal feedback, respectively. Finally, numerical simulations are given to demonstrate the effectiveness of the proposed method.