New controllability condition for siphons in a class of generalised Petri nets

Over the last two decades, a number of deadlock control policies based on Petri nets were proposed for flexible manufacturing systems (FMSs). As a structural object of a Petri net, siphons are widely used in deadlock control. For system of sequential systems with shared resources ((SR)-R-4), the current deadlock control policies based on max or max'-controlled siphons tend to overly restrict the behaviour of a controlled system. The controllability conditions of a siphon are relaxed by a new concept called max ''-controlled ones. We conclude that an (SR)-R-4 is live if all its siphons are max ''-controlled. Compared with the existing ones, the proposed one is more general. Examples are given to illustrate it.