A 4-BLOCK PROBLEM FOR H-INFINITY DESIGN - PROPERTIES AND APPLICATIONS

In this paper, we introduce and study a certain 4-block H infinity optimal control problem from the point of view of its usefulness as a control system design tool. The problem is a natural generalization of several H infinity optimal control problems e.g. mixed sensitivity and gap/normalized-coprime-factor optimization. We show that the problem is well-posed in the sense that the optimal performance depends continuously on the plant, where perturbations are measured in the gap metric. Two illustrative examples are given including a design for a flexible structure.