Application of SDRE Technique to Orbital and Attitude Control of Spacecraft Formation Flying

In this paper a nonlinear control technique for coupled orbital and attitude relative motion of formation flying is presented. Future spacecraft formations will exploit very low inter-satellite range for enhance in-space maneuvers and operations, so high performances in autonomous control will be required. The proposed control system is based on the solution of the State-Dependent Riccati Equation (SDRE), which is one of the more promising nonlinear techniques for regulating nonlinear system in all the major branches of engineering. The coupling of the relative orbital and attitude motion is obtained considering the same set of thrusters for the control of both orbital and attitude relative dynamics. In addition, SDRE algorithm is implemented with a timing strategy both for the controller and the proposed nonlinear filter. An up-to-date formation mission, which is ESA Proba-3, constitutes the test-bed for the designed control system. Numerical simulations considering a tracking signal for both orbital and attitude relative maneuver during an operative orbit of the mission are presented.