Robustness in the presence of mixed parametric uncertainty and unmodeled dynamics

Abstract

Continuing the development of the structured singular value approach to robust control design, the authors investigate the problem of computing μ in the case of mixed real parametric and complex uncertainty. The problem is shown to be equivalent to a smooth constrained finite-dimensional optimization problem. In view of the fact that the functional to be maximized may have several local extrema, an upper bound on μ whose computation is numerically tractable is established; this leads to a sufficient condition of robust stability and performance. A historical perspective on the development of the μ theory is included.