Robust supervisory control of discrete event systems with model uncertainty

Abstract

Discrete event systems (DESs) represent many important engineering systems such as communication networks, computer networks, manufacturing systems, and transportation systems. State variables in such systems change their values only at discrete instants of time, and more importantly such changes are driven by occurrence of discrete-events. DESs are recognized as a new breed of dynamic systems that are structurally different from the conventional models characterized by ordinary differential equations. The control of DESs called supervisory control is recognized as one of effective tools for the analysis and control of large scale dynamic systems which are one of the biggest challenges facing control engineers today. The goal of supervisory control is to achieve desirable logical performances for a given system through feedback control. Of particular interests are model uncertainty and robust control problems which provide a key to solve practical problems. However, it is difficult to approach them using tools from the existing literature taking no account of model uncertainty. In this dissertation we study various schemes on model uncertainty and robust control problems of DESs. First, as a framework on model uncertainty, we introduce multiple model representation where a DES is modeled as a set of some possible models. In the scheme we address a fault-tolerant control problem of DESs under partial observation. As a result, we present the conditions for the existence of a robust supervisor which guarantees a fault-tolerant behavior for any model in the set. Second we introduce nondeterministic models describing nondeterminism in the transition which implies the unobservable aspect or lack of the information of system behavior. In the scheme we handle nondeterministic models using multiple deterministic model approach and language models approach subject to a nonblocking control problem. In the multiple deterministic model approach, it is shown that a superv...