Numerical investigation of magnetic only attitude control for small satellites

The subject of the thesis research is the study of the attitude control for small satellites actuated by only magnetorquers, which presents interesting control challenges due to the time-variance and underactuation of the system. It is indeed known that for underactuated systems, the presence of external disturbances can lead to system instability. Even if the problem of finding a robust non-linear global controller has been already investigated, there is still room for improvements. In this regard, the present work proposes a solution in which the elements of the averaging theory for a system subjected to exogenous input can be combined with that of the sliding mode control theory based on a classical optimal sliding manifold, providing the feedback system with robustness against disturbances. The proposed approach is applied to design an Earth-pointing attitude control system for the ESEO spacecraft in Low Earth Orbit. The results of simulations suggest that the sliding mode control as robust control feedback provides good performances in the presence of external disturbances, measurement noises, and inertia uncertainties.