Attitude coordination control of formation flying satellites under control saturation

The problem of the attitude coordination control under control input saturation for formation flying satellites is investigated, and a nonlinear saturated coordination controller is proposed. Different from the case of the attitude control for single satellite under input constraints, in which a hyperbolic tangent function is usually chosen, a new continuously differentiable nonlinear saturation function vector is introduced to ensure that the continuous control input is bounded and make the stability analysis of the attitude coordination system available. Based on the feature that the closed-loop attitude coordination system belongs to autonomous systems or non-autonomous systems respectively according to different values of the desired and tracked angular velocity, LaSalle's invariance principle and Barbalat's lemma are utilized correspondingly to analyze the stability of the attitude coordination controlled system in different cases, then the result of the asymptotical stability is obtained. Simulation results show that this kind of nonlinear coordination controller can achieve the purpose of attitude coordination for formation flying satellites, and guarantee the control input is bounded as well.