A METHOD FOR ROBUST STABILIZATION

Let P(y, M) be a family of polynomials, depending on a controller para meter vector y in R(n+1), defined as follows: M : = {m = (m(ij)) : m(i j) is-an-element-of [a(ij), b(ij)], 0 less-than-or-equal-to i, j less- than-or-equal-to j less-than-or-equal-to n} a family of interval matri ces, and y in R(n+1), set P(y, M) : = {p0 + p1 s + ... + p(n) s(n) : ( p0, ..., p(n))' = M . y for some M in M}. Given an initial stabilizing controller y0, this paper provides a simple method to robustify y0, i .e., to obtain a controller parameter vector y1 which is more robust t han y0. Furthermore we define the stability factor t for a given robus tly stable controller y, which serves as a measure of the robustness o f y.