Disturbance observer backstepping sliding mode agile attitude control of satellite based on the anti-saturation hybrid actuator of the magnetorquer and magnetically suspended wheel

This paper presents a new anti-saturation strategy to avoid external singularity, improve reliability, and fast maneuvers of a satellite by combining the novel three-dimensional magnetically suspended wheel (3-D MSW) actuator and magnetorquer. The MSW is the preferred actuator for agile maneuvering compared to the traditional control moment gyro due to frictionlessness, low vibration, and long lifetime. The anti-saturation strategy includes 3-D MSW arrangement with pyramid configuration and three orthogonal magnetorquers. A steering law is designed to distribute control torque between actuators by calculating command tilt angles of the 3-D MSW and magnetic dipoles of the magnetorquer. A nonlinear disturbance observer backstepping sliding mode controller is designed to control the rotor shaft of 3-D MSW for agile maneuvers and desaturate it with the magnetorquer despite high-frequency disturbances. Finally, simulation results of attitude control based on anti-saturation hybrid actuators demonstrate the effectiveness and accuracy of agile maneuvers. Compared with usual steering laws, simulation outcomes confirm the proposed method and desaturate the 3-D MSW system when it experiences a maximum workspace and does not have extra angular momentum.