Structured stability robustness improvement by eigenspace techniques- A hybrid methodology

A new hybrid design technique for improving stability robustness with respect to block-structured perturbations in multivariable linear feedback systems is presented. This new methodology is hybrid in that it uses both constrained optimization techniques for robustness and eigenstructure assignment for performance. This approach allows the designer to treat simultaneous perturbations occurring at different locations in the feedback system without having to compromise between robustness and performance. Performance requirements expressed in terms of closed-loop eigenvalues and right-eigenvectors are directly satisfied by the procedure. The realistic example of the SA365N DOLPHIN helicopter is presented to highlight the merits and some of the concerns in using this methodology.