Fault monitoring of automated manufacturing systems by first order hybrid Petri nets

Fault monitoring plays an important role for safety and reliability of industrial systems. We present a novel on-line monitoring technique for automated manufacturing systems employing the first order hybrid Petri nets formalism, i.e., Petri nets making use of first order fluid approximation. The proposed fault analysis approach belongs to the class of event based methodologies, so that the state space explosion problem is avoided. Moreover, the presented technique relies on a modular framework: elementary monitors can be connected with other monitors to check complex systems. Timely and accurate detection of system failures is ensured, i.e., faults are detected before the maximum execution time assigned to each task. An application to an automated manufacturing system proposed in the related literature enlightens the simplicity and modularity of the technique.