Adaptive Fixed-Time Refined Disturbance Observer-Based Composite Control for Gimbal Servo System With Multiple Disturbances

Ensuring fast and accurate velocity-tracking performance of the control moment gyro gimbal servo system under multiple disturbances is crucial for high-precision attitude control of spacecrafts. Driven by the aforementioned demands, an adaptive fixed-time refined disturbance observer-based composite control scheme is proposed in this article. First, a gimbal servo system model is established by finely characterizing multiple heterogeneous disturbances and parameter perturbations under the difficulty of obtaining accurate rotor velocity. Then, an adaptive fixed-time refined disturbance observer framework is constructed to estimate multiple disturbances with unknown dynamics by fully utilizing disturbances prior information. Combined with observation results, a modified fixed-time controller with a novel fast terminal sliding mode surface is designed to compensate for matched and mismatched disturbances and ensure high-accuracy velocity tracking within a fixed time. Finally, experiment results confirm the validity of the proposed scheme.