Decentralized robust saturated attitude coordination control of satellites within formation

The attitude coordination control problem for formation flying satellites associated with time-varying reference attitude tracking subject to control input saturation is investigated in this paper. According to different cases, three kinds of continuous and bounded coordination controllers are proposed with the novel use of hyperbolic tangent functions. Firstly, an ideal saturated coordination controller is presented in the absence of external disturbances and parametric uncertainty. Furthermore, taking account of unavailability of measurements of angular velocities, passive filters are applied to the angular-velocity-free feedback saturated coordination controller design. When external disturbances and parametric uncertainty exist, by introducing some dynamic time-varying parameters in the hyperbolic tangent functions, a continuous robust saturated coordination controller is proposed. Due to the fact that the closed-loop coordination systems under these algorithms are non-autonomous, Barbalat's lemma is utilized properly for convergence analysis of states. Simulation results are provided to show the effectiveness of the proposed control schemes.