Supervisory control of timed discrete-event systems under partial observation

This paper extends the authors' previous work on observability of discrete-event systems by taking time into consideration. In a timed discrete-event system, events must occur within their respective lower and upper time bounds. A supervisor can disable, enable, or force some events to achieve a given control objective. The authors assume that the supervisor does not observe all events, which is often the case in practice. The authors generalize the concept of observability to timed discrete-event systems and show that it characterizes the existence condition for a supervisor. The authors also generalize normality, a stronger version of observability, to timed discrete-event systems, which has nice properties that are absent in observability. The authors then derive conditions under which observability and normality are equivalent. The authors propose two methods to synthesize a supervisor, a direct approach and an indirect approach. An example is given to illustrate the results. >