Attitude control of satellites with flexible appendages: a structured H? control design

In this paper, the modeling of flexible multi-body systems (typically a satellite), the design of a reduced-order robust controller and the closed-loop system robustness analysis are considered. First, we present a generic tool developed to build the model of a multi- body dynamic system taking into account parametric uncertainties for robust control and analysis purpose. Satellites are typically composed of a main body (hub of the satellite) and cantilevered appendages (flexible or not). Based on the description of each element(mechanical and geometrical properties, uncertain parameters ...), a linear model between torques applied to the hub (control or perturbation inputs) and angular accelerations is built using the Linear Fractional Representation framework. Second, based on this model, a control design method is proposed: from a basic standard scheme and the latest H_infinity solver, a low order H1 controller can be derived. Roll-off requirements and worst-case parametric configurations can also be taken into account in a multi-model design approach. Third, robustness analysis of the design on the full order model is considered. A numerical example illustrate the relevance and effectiveness of the proposed approach.