H∞ controller design for uncertain multiple-time-delay systems

Abstract

In this dissertation, H∞ controller design for systems with multiple uncertain time-delays is studied. In the H∞ controller design for these systems, since the nominal time-delays are taken outside the generalized plant, the uncertainty block of the overall system may become non-causal. However, the H∞ controller is designed by the small-gain theorem, which assumes the causality of the feedback interconnected subsystems. To alleviate this difficulty, the sufficient conditions are derived to satisfy the validity of the small-gain theorem for feedback interconnection of non-causal systems. Utilizing these results, an optimal H∞ flow controller is designed for data-communication networks. Stable H∞ controller design is also studied and different design approaches are presented. Furthermore, to satisfy one of the time-domain requirements of the flow controller, sufficient conditions are introduced to choose the free parameter in the structure of the designed controller.