Active disturbance rejection control for spacecraft relative motion in libration point orbits subject to actuator saturation and time-delays

In this paper, a novel ADRC scheme is introduced for a class of spacecraft relative motion system with actuator saturation and time-delays. The relative kinematics and dynamics between two spacecrafts are modeled with dual quaternions to avoid singular points. A set of dimensionless variables is introduced to improve the computation accuracy. Considering communication time-delays and actuator saturation, an extended state observer with time-delays predictor and an anti-windup compensator are designed. Then, a composite controller is designed to eliminate the total disturbances. Finally, the effectiveness of the proposed methodology is verified for the spacecraft rendezvous and docking system.