Valentin PREDA soutiendra sa thèse intitulée "Robust Microvibration Control and Worst-case Analysis for High Pointing Stability Space Missions", le 13 décembre, à partir de 10h, dans la Salle de Conférences du laboratoire IMS (Bât A31).
Résumé: The PhD thesis deals with the problem of microvibrations mitigation in observation satellites that require a high pointing stability and draws expertise from the University of Bordeaux, the European Space Agency (ESA) and Airbus Defence and Space. The work deals with the robust control design and worst-case analysis of an active microvibration isolation system for observation satellites. It involves the synthesis of a robust Linear Parameter Varying (LPV) controller as well as the physical modeling of the uncertain and time-varying model of a flexible spacecraft actuated by a spinning reaction wheel. It relies on an analysis based on the structured singular value (mu) and Integral Quadratic Constraints (IQCs), in order to obtain robust performance guarantees and robust margins. A new theoretical model of harmonic disturbances generated by a spinning reaction wheel has been developed. Combined with the uncertain dynamical model of a flexible satellite it is shown how this disturbance model can be used to tune an active vibration isolation system and to guarantee a set of pointing stability requirements, even in the presence of parametric uncertainties, time-varying reaction wheel spin rates, actuator saturation and time-delays. The benefits of this novel end-to-end model based tuning approach are also highlighted by comparing nonlinear simulation results with the ones predicted using analytical tools (mu and IQCs). It is shown how these tools can reliably complement time-consuming Monte-Carlo campaigns and deliver precise and valuable guarantees on the pointing performance of an observation satellite that requires high pointing stability.