An effective FMS deadlock prevention policy based on elementary siphons

Based on siphons, a variety of techniques are developed for the deadlock problems in flexible manufacturing systems. The major disadvantage of the existing approaches is that the number of siphons that have to be considered is large or grows fast as these methods proceed. In this paper, we investigate the deadlock prevention problem in a class of Petri net (PN), S³PR, where siphons are distinguished by elementary and redundant ones. For each elementary siphon, a monitor is added to prevent it from being emptied without generating emptiable control-induced siphons. The results show that a more permissive liveness enforcing Petri net supervisor with a small number of additional monitors can be obtained by our deadlock control policy.