Robust regional eigenvalue-clustering analysis for linear perturbed discrete time-delay systems

In this work, under the assumption that all the eigenvalues of the linear n ominal discrete time-delay system lie within certain specified regions, a s ufficient condition is proposed to preserve the assumed property when struc tured parameter perturbations are added into the linear nominal discrete ti me-delay system. No restriction is imposed on the shapes of the specified r egion. When all the eigenvalues are required to locate in stable regions, t he proposed criterion will become the stability robustness criterion. For t he case of a circular region, two examples are given to show, numerically, that the proposed criterion may obtain better results than those reported r ecently.