Control of double gimbal control moment gyro systems using the backstepping control method and a nonlinear disturbance observer

Abstract

To cancel the negative effects of the friction torques, unmodeled dynamics, and coupling torques, affecting the gimbal precision of a double gimbal control moment gyro (DGCMG) system, this paper proposes a new control architecture to handle these exogenous/endogenous disturbances and to control the two gimbals of the system. It combines a backstepping controller with a nonlinear disturbance observer, which preserve the advantages of the two entities. Firstly, the state space equations of the DGCMG system are established with the friction torques considered exogenous disturbances and unmodeled dynamics regarded as endogenous disturbances. Secondly, a nonlinear observer is used for the estimation of the disturbances. Thirdly, using the observer estimation errors, a backstepping controller is designed to enhance the robustness of the control system, to handle the channel interferences, and to solve the mismatched problem without decoupling between the inner/outer gimbal channels. The obtained control architecture is software implemented and validated; the results show that the proposed control approach not only enhances the robustness in relation to the exogenous/endogenous disturbances, but also improves the angular velocity precision of the two gimbals of the DGCMG system.