Development of a Petri net-based fault diagnostic system for industrial processes

For the improvement of the reliability and safety of industrial processes, a fault detection and tracing approach has been proposed. In this paper, the P-invariant of Petri nets (PN) is applied to discover sequence faults, while both sensor faults and actuator faults are detected using exclusive logic functions. For industrial applications, the proposed fault detector has been implemented within a programmable logic controller (PLC) by converting the fault detection logic functions into ladder logic diagrams (LLD). Moreover, a fault tracer has been modeled by an AND/OR tree and a tracing procedure is provided to locate the faults. A mark stamping process is demonstrated as an example to illustrate the proposed diagnostic approach.