On the design of robust controllers using the interval Diophantine equation

In this paper the design of pole placement feedback controllers for interval plants is addressed within an interval analysis framework. Three main topics connected by the concept of interval Diophantine equation are treated: a relatively straightforward investigation about robust coprimeness of interval polynomials, a reliable computing approach for the design of pole placement controllers in the presence of inaccuracies of the interval type, and the design of robust controllers with regional pole placement specifications. After explicitly characterizing a convex subset of robust controllers, the problem of designing non-fragile controllers is formulated as a centering problem, which is then solved by a global optimization algorithm. Numerical examples illustrate the main characteristics of the approach proposed