Design of a more permissive and structurally simple liveness-enforcing Petri net supervisor for flexible manufacturing systems

This paper develops a deadlock prevention policy for a class of Petri nets which can model flexible manufacturing systems, where deadlocks are caused by unmarked siphons. We distinguish emptiable siphons in a plant Petri net model by elementary and redundant ones. By adding a monitor for each elementary siphon, all redundant siphons can be controlled. Furthermore, by checking the redundancy of the additional monitors, we can remove some monitors added, which leads to a more permissive and structurally simple liveness-enforcing Petri net supervisor.