Controller parametric robustification using observer-based formulation and multimodel design technique

This note deals with controller robustification using equivalent observer based structure. The purpose of the method is to improve the parametric robustness of an initial controller, synthesized, for example, by using the LQ,H_∞, or μ technique. The method uses equivalent Luenberger observer formulation and multimodel design procedure for the parametric robustification. First, the initial controller is put under equivalent observer structure. Second, from this observer-based formulation, the controller is reshaped to increase the parametric robustness without paying attention to the closed-loop poles coming from the controller dynamics. Note that during this step, changes in the controller initial performances are minimized. Another advantage of the equivalent observer based formulation lies with the fact that it could directly be used to schedule the controller (dynamic and feedback parts). Finally, the global method (equivalent observer plus robustification) is applied on the robust control of the space shuttle described in μ-analysis and synthesis toolbox.