Composite Controller Design for Flywheel Based on Disturbance Observer and Robust PI Control

Abstract

Flywheel is widely applied in the attitude control system(ACS) of the spacecraft as actuator, but friction torque caused by flywheel has been a difficult problem reducing the accuracy and stability of the ACS. This paper concerns the disturbance attenuation and rejection problem for flywheel system, and a new composite control scheme is presented. A disturbance observers (DO) is designed to reject the friction torque by feedforward compensation, and PI controller optimized by H∞ method is designed to control the wheel speed and attenuate other unmodeled disturbances, furthermore, input saturation problem is considered also. Finally, simulations for flywheel control system show that by combining the DO with conventional control law, disturbances can be attenuated and rejected and the dynamic performances are enhanced.