Control of Distributed Parameter Systems with Spillover using an Augmented Observer

Modern modal control methods for flexible structures, based on a truncated model of the structure´s dynamics, have control and observation spillover which can reduce the stability margin of the controlled structure. The sensor output is often filtered to reduce observation spillover, however, it introduces signal distortion which perturbs the closed-loop system pole locations. This can reduce stability margins and jeopardize convergence of the observer. When the filter equation is included in the standard observer equations the separation principle between the controller and the observer will no longer holds, and the closed-loop poles cannot be located using standard pole placement methods. A new method is presented, where a first order filter is included in an augmented observer. The separation principle, and controllability and observability properties of the original system are shown to remain when using the augmented observer. Filter and spillover produced pole perturbations in the different methods are illustrated with a numerical example.