Stabilization by output feedback revisited

Abstract

1 Simplicity, elegance and robustness of design methods based on root-locus properties are hardly matched by any other method for feedback design. However, these methods tend to loose their effectiveness in the challenging problem of (robustly) stabilizing, via output feedback, an unstable and non-minimum phase system. In this paper, we illustrate a simple concept leading to a recursive design method for stabilization by output feedback, which inherits most of the benefits, and overcomes a number of drawbacks, of the classical design methods based on root-locus properties. Of course, this does not lead to any specific breakthrough in the case of linear systems, where the solution of a diophantine equation would suffice, but opens a totally new perspective in the problem of robustly stabilizing, via output feedback, a possibly unstable and non-minimum phase nonlinear system.