Composite Decoupling Control of Gimbal Servo System in Double-Gimbaled Variable Speed CMG Via Disturbance Observer

In order to realize the decoupling and disturbance rejection control of the inner and outer gimbal system under two working conditions of a double-gimbaled variable speed control moment gyroscope (DGVSCMG), this paper presents a composite controller based on the disturbance observer and state feedback control. We first developed a dynamic model of a double-gimbal servo system, and analyzed the system characteristics of coupling and mismatched disturbance in CMG and flywheel working modes. Then, we propose a novel decoupling method through regarding the coupling term as systems lumped disturbance. The system disturbance was estimated by the designed disturbance observer and was rejected via the proposed composite controller combining a state feedback method. Finally, we proved the overall system stability by using a Lyapunov approach and derived an estimated upper bound of the state variables to guide controller parameters selection. We concluded from simulation and experimental results that the proposed method was effective in decoupling and disturbance compensation control of the DGVSCMG double-gimbal servo system, and enhanced system disturbance rejection and speed servo performance.