Comparison of Adaptive Control Laws on a Satellite Attitude Control Benchmark*

The CNES satellite DEMETER is taken as a Benchmark to test several control laws. The original control strategy for this mission was to switch between two different control laws according to the pointing error. This switching control made its proof on this mission, but it induces some unwanted behaviour such as oscillations in the control torque at the appearance of the switch and long-time responses. In this work, we compare the switching control with continuous adaptive control laws that avoid discontinuities, allow a wider range of initial conditions, and have faster convergence. Three adaptive control laws are described and compared: (i) the DEMETER switching control, (ii) a robust adaptive control where gain evolution is driven by the attitude pointing error, and (iii) a sliding mode control with an adaptive sliding surface. The obtained closed-loop performances are illustrated in small and large pointing error situations.