An Extension of Kharitonov´s Theorem and its Application

Kharitonov\´s Theorem, shown first in a Russian literature only within this decade, gives an exact stability condition for polynomials with perturbed coefficients. This theorem seems to have enormous potentialities in the analysis and design of robust control systems. In this paper, an attempt is made to extend the theorem to cover a class of time-delay systems. The results obtained are applied to study "interval stability with respect to system parameters" of feedback control systems with a time-delay element.