A Siphon Solution Method In A Subclass Of Petri Nets And Its Application

Using Petri nets to design a flexible manufacturing system is an important task in the study of Petri nets. Getting all strict minimal siphons (SMS) is the premise of deadlock prevention strategies based on siphon theory. However it is very time- consuming when the size of the system is large. Adding a control place for each strict minimal siphon will also make the net more complex.In order to solve these problems, a technique to find all SMS in a subclass of Petri net is developed in this thesis. Since the new method makes use of the structure of the net, much time is saved. After getting all of the SMS, the elementary siphons can be obtained. The elementary siphons can be invariant-controlled by adding control places and arcs, and the controllability of a dependent siphon may be ensured by that of its related elementary siphons. Finally, a liveness-enforcing supervisor can be producted.Combining the novel siphon solution method with elementary siphons based theory, a new deadlock prevent policy is developed. Compared with other deadlock prevention strategies, it can make the structure of the supervisor simpler. An optimal controller can be generated with less computational cost using the new policy.