| A new framework of hybrid systems, based on discrete event systems and real time systems, is presented in this work. First, we revisit observability of discrete event systems defined by Lin and Wonham. We show that although the original definition is intended for event observation with projection, its significance goes beyond its original intent. Specifically, we show that (1) supervisory control with state observation can be studied in terms of event observation; (2) supervisory control problems with event mask can be converted to problems with event projection; and (3) nondeterminism is closely related to unobservability. These results are important for supervisory control of hybrid systems.;Second, we present the architecture of a class of hybrid systems. Based on structured analysis and design methods, we propose a structured separation principle which sets up an interface between the discrete parts and continuous parts of real time systems and environment. The discrete parts are modeled by discrete event systems which we discuss in this thesis and a hierarchical data flow diagram describes continuous parts. Differential equations are for specifications of the hierarchical data flow diagram. The discrete event systems supervise and synchronize the hierarchical data flow diagram. We illustrate the main features by a cruise control example.;Finally, we propose a control framework for hybrid systems, based on our model. The concepts of controllability and observability of hybrid systems are introduced to ensure the existence of controllers, and analysis and synthesis of hybrid systems are discussed. We also study the supervisory control of hybrid systems. |
