ABSTRACT
This paper is a revision of two papers concerning the D-stability of control systems. In the first part the D-stability of a polynomial is investigated. Thereby the domain D is defined by a rational function f(jω). A criterion for the polynomial P(z) to be D-stable is derived in the frequency domain using the Nyquist criterion. These results are extended to the D-stability of a family of interval polynomials in the second part of the paper. A test for the stability domain D to be a Kharitonov region, i.e. a region where the stability of the family of polynomials follows from the stability of all vertex polynomials, is presented.
