High-Precision Composite Control Based on Dual-Sampling-Rate Extended State Observer for Ultra-Low Speed Gimbal Servo System

This article aims to deal with the speed control performance of the gimbal servo system at ultra-low speed to guarantee the accuracy of the output torque of the control moment gyroscope (CMG). The main factors leading to the speed fluctuation of the gimbal servo system are the speed measurement error and disturbance torque. This article proposes a composite controller that consists of the dual-sampling-rate reduced-order extended state observer (DSRESO) and sliding-mode controller (SMC) in the speed loop so as to improve the speed control performance at ultra-low speed. DSRESO is designed to deal with the speed measurement as well as the disturbance estimation in ultra-low speed conditions. Then, the SMC-based DSRESO is applied for speed closed-loop control so as to suppress the speed fluctuation of the gimbal servo system under ultra-low speed and disturbance torque conditions. The feasibility and effectiveness of the proposed control scheme have been verified by the simulations and experiments compared with other methods. Also, the resultant effect is that the speed tracking precision of the gimbal servo system at ultra-low speed is improved significantly.