Coordinative coupled attitude and orbit control for satellite formation with multiple uncertainties and actuator saturation

This paper studies the coordinative coupled attitude and orbit control system (AOCS) of a satellite formation composed of one microsatellite and two 3U CubeSats. It is described as a highly nonlinear and coupled system subject to actuator saturation and multiple uncertainties including parametric perturbations and external disturbances. To address this issue, the centralized architecture and leader-following method are adopted in the formation firstly. The closed-loop system of each satellite member is divided into orbit and attitude control loops respectively. The coupling relationship between orbit and attitude is introduced as a constraint of the control law. Then a robust controller consisting of a nominal controller, a robust compensator and an advanced proportional-derivative (APD) controller is proposed to achieve high-accuracy formation control. The robust compensator is constructed from an auxiliary system and a finite-time observer to compensate the influence of an equivalent lumped disturbance. The APD controller is developed to achieve desired performances under actuator saturation. Stability analysis indicates that both relative position errors and attitude tracking errors can converge asymptotically. Finally, numerical simulations are carried out to verify the effectiveness of proposed control law in both relatively-stationary and fly-around scenarios.