Improved upper bounds of the structured singular value

Takes a new look at the mixed structured singular value problem. Several new upper bounds are proposed using a very simple approach which the authors call the multiplier approach. These new bounds are convex, computable by using the linear matrix inequality (LMI) method, and numerically efficient in many robust stability problems. The authors show, most importantly, that these upper bounds are actually lower bounds of a well-known upper bound which involves the so-called D-scaling (for complex perturbations) and G-scaling (for real perturbations)