Adaptive periodic-disturbance observer based composite control for SGCMG gimbal servo system with rotor vibration

This paper presents an adaptive periodic-disturbance observer (APDO)-based composite control scheme to attain accurate velocity-tracking control for the single gimbal control moment gyro (SGCMG). Firstly, a modified periodic-disturbance observer (PDO) is proposed to estimate both the fundamental wave and harmonics of the rotor vibration. Secondly, to ensure the estimation accuracy under variable rotor speed, an APDO is proposed by combining an adaptive frequency estimator with the modified PDO. Integrating with the PI controller, the proposed APDO-based composite control scheme can effectively reduce the influence of rotor vibration, friction, and parameter uncertainties, thereby improving control accuracy. Furthermore, performance and stability analyses show that the observer can achieve accurate estimation under arbitrary initial conditions. Finally, numerical and hardware-in-the-loop simulation results are given to demonstrate the robustness and effectiveness of the proposed scheme.