A Hybrid Scheme of Feed-forward/Feedback Control for Vibration Suppression of Flexible Spacecraft with On-Off actuators during Attitude Maneuver

This investigation is to apply the so-called component synthesis vibration suppression (CSVS) based feed-forward control and the conventional PD feedback control to the vibration control of a flexible spacecraft. The proposed control design process is two fold: design of the attitude controller followed by the design of a flexible vibration attenuator, the feed-forward controller. The Lyapunov technique is applied in the design of the attitude controller, which is able to asymptotically stabilize the flexible spacecraft system. The feed-forward controller based on CSVS method is designed for the reduction of flexible vibration by modifying the command input, which only requires information about the natural frequency and damping of the closed-loop system including the attitude controller. Additionally, to extend the CSVS method to the system with the on-off actuators, the pulsewidth pulse-frequency (PWPF) modulation is introduced to control the thruster firing and integrated with the CSVS method. PWPF modulation is a control method that provides pseudo-linear operation for an on-off thruster. The proposed control strategy has been implemented on a flexible spacecraft, which is a hub with symmetric cantilever flexible beam appendage and can undergo a single axis rotation. The results have been proven the potential of this technique to control flexible spacecraft.