Robust attitude coordination control of formation flying spacecraft under control input saturation

The attitude coordination control problem for formation flying spacecraft 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 use of hyperbolic tangent functions, a fundamental controller is presented for an ideal case. Accounting for unavailability of measurements of angular velocities, passive filters are applied to the velocity-free ordination controller design. When parametric uncertainty and external disturbances exist, by introducing some time-varying parameters in nonlinear saturation functions and constructing an adaptive parameter estimation term, a robust coordination controller is proposed. Barbalat's lemma is utilized properly for stability analysis of the closed-loop non-autonomous coordination systems. Simulation results are provided to show the effectiveness of the proposed control schemes.