Restarting Manufacturing Systems; Restart States and Restartability
Fault monitoring is an essential requirement for safety and reliability of dynamic systems. Motivated by the fact that a large class of dynamic systems can be viewed as Discrete Event Systems (DESs) at some level of abstraction, the paper presents a novel event-based approach for DES on-line monitoring, ensuring timely and accurate detection of system failures. The monitor model is based on first order hybrid Petri nets, i.e., Petri nets that make use of first order fluid approximation. The proposed fault analysis technique relies on a modular framework, so that elementary monitors can be connected with other monitors to check more complex systems while avoiding the state space explosion problem. In addition, the presented monitor detects system faults as soon as possible, before the maximum execution time assigned to each task. An application to a simple manufacturing system enlightens the simplicity and modularity of the technique.