Attitude tracking control for a space moving target with high dynamic performance using hybrid actuator

Abstract Attitude tracking control for a space moving target (such as debris or malfunctioning satellite) is investigated in this paper, which is different from the traditional agile attitude maneuvering and tracking control, and is a challenging problem for attitude control system, requiring agility, large control torque output, and high dynamic accuracy, etc. The rapidly moving target and spacecraft pose several tough issues such as agile attitude tracking control and actuator configuration design. A novel attitude tracking strategy is proposed to tackle the dynamic imaging process, including three phases, earth observation, attitude adjustment and dynamic tracking phase. With the accomplishment of attitude adjustment, the spacecraft will point toward the target to start the imaging task. For the maneuvers in the attitude adjustment and tracking phases, a combined control strategy consisting of saturation controller and backstepping controller is proposed. The former one constrains the attitude angular velocity as well as the required momentum on the actuators during the initial phase, while the backstepping controller guarantees the control accuracy with high dynamic performance in the imaging phase. A hybrid momentum exchanging actuator consisting of Control Moment Gyro (CMG) and Reaction Wheel (RW) is introduced to satisfy the great control torque demand. Null motion strategy is derived for the hybrid actuator to deal with CMG singularity and RW saturation simultaneously. Numerical simulations have demonstrated the advantages of the hybrid actuator and the proposed attitude control strategy, which not only enables the spacecraft to maneuver rapidly but also guarantees the tracking accuracy.