Robust Attitude Control Systems for Small Satellites

摘要

In this paper, an Attitude and Orbit Control System (AOCS) robust flight software has been designed and tested. The proposed attitude control law is based on a Tube-based Robust Model Predictive Control (TRMPC). The proposed TRMPC control system, differently from a Classical MPC, is able to effectively manage system uncertainties and external disturbances according to a proper design of the "tube" and system constraints. Indeed, a TRMPC controller is robust, by definition, against system disturbances, provided that such disturbances are bounded by a well-defined convex set. In addition, a proper design of the "tube" by a Linear Matrix Inequalities (LMI) approach ensure robustness against system uncertainties as well. For example, uncertainties in the spacecraft inertia and limited, and bounded, orbital disturbances, typical of a Low Earth Orbit (LEO) environment, can be effectively managed by a TRMPC-based AOCS. The effectiveness of the proposed control system is shown for two different spacecraft, in a precise pointing telecom maneuver.