REGULARITY CONDITIONS FOR THE STABILITY MARGIN PROBLEM WITH LINEAR DEPENDENT PERTURBATIONS

In this paper, the problem of continuity of the stability margin of a control system on problem input data is addressed. The case in which p erturbations are linearly correlated is considered. It is shown that t he existence of special points (called critical points) in the stabili ty boundary manifold in parameter space plays a key role in the analys is of the problem. Several conditions, either sufficient or both neces sary and sufficient, are given, ensuring continuity of the stability m argin on problem data. The obtained conditions turn out to be easily c heckable for practical applications. Numerical examples are presented to illustrate the proposed techniques.