Robust coordinated control of satellite formations subject to gravity perturbations

In this paper, we address the coordinated control of leader/follower satellite formations, in presence of gravitational J₂ perturbation. We derive a robust, decentralized controller which makes use of measurements of the relative position error between the follower satellite and the leader of the formation. The controller is designed using an internal model based approach. Internal models of the reference trajectories and of the gravitational disturbance are employed to generate autonomously the control required to induce a "natural" invariant motion on a specified orbit, which is then rendered semi-globally attractive by means of a dynamic stabilizer. The proposed methodology handles parametric uncertainties, unknown disturbances and uncertainties on the reference trajectory in a simple, unifying fashion. The resulting controller architecture allows the problem of formation planning and formation reconfiguration to be cast as a synchronization problem for controlled linear oscillators.