Diagnosability enforcement in labeled Petri nets using supervisory control

In this article, we deal with the active diagnosis problem in labeled Petri nets by developing a supervisor for a plant such that the closed-loop system is diagnosable. Since control actions may introduce deadlocks even if an original plant is deadlock-free, we first generalize the classical notion of diagnosability in labeled Petri nets to the nets that may contain potential deadlocks. To avoid enumerating all reachable markings of a plant, we develop a structure called quiescent basis reachability graph, and accordingly propose a structure named Q-diagnoser to verify the diagnosability of a net. We prove that a plant is diagnosable if and only if there does not exist any indeterminate cycle in its Q-diagnoser. Finally, for an undiagnosable plant, we introduce a diagnosability enforcing supervisor to enforce the diagnosability by trimming a Q-diagnoser. Moreover, our approach guarantees that the closed-loop system cannot reach a dead marking unless a fault transition has fired. (C) 2021 Published by Elsevier Ltd