Monitoring of timed discrete events systems: Application to manufacturing systems

In this paper, we develop a method for fault detection based on Stopwatch automata. This method takes into account the exact behavior of some physical resources. Because of a malfunction, some system tasks can be stopped and resumed a little later. Thus, we introduce the concept of an acceptable system behavior which is supposed to be observable. It is supervised by two clocks for each task. The timed state space of the stopwatch automaton delimits exactly the acceptable system behavior. It permits to detect the fault as early as possible. This space is a set of the inequality constraints where any violation of these constraints represents a fault.