Robustness analysis of feedback systems with block-diagonal structured uncertainties

The results for magnitude-bounded diagonal perturbation are extended to norm-bounded block-diagonal perturbation. A useful consequence to this extension is that an easily computable upper bound for the structured singular value via suboptimal diagonal similarity scaling is obtained. It is concluded that the results are applicable to a wider class of perturbations, i.e. the norm which bounds the perturbation p in this study need not be the 2-norm (maximum singular value). In the scalar case, this does not give much advantage, as all pth-norms reduce to the magnitude of the element. However, in the matrix case, different norms would characterize different types of perturbations