Analysis of systems with combined time invariant/time varying structured uncertainty

Robustness analysis is considered for systems with structured uncertainty involving a combination of linear time-invariant and linear time-varying perturbations. An exact /spl mu/ test for analysis is presented, based on a finite augmentation of the original problem. Sufficient conditions based on scaled small-gain are considered for this case, and the class of perturbations for which these conditions become necessary is characterized.