Avoiding Deadlock With Uncontrollable Transitions In Petri Net

Deadlock in Petri net has been an important direction of Petri net researchwork since two since last two decades. Deadlock was a very important problemthat must be consider for designing and controlling flexible manufacturingsystem. For a net model, we first find the deadlock nodes, and then try to controlthe deadlock nodes by some methods, to make the net live.In this research, we develop a new deadlock detection policy. By using thereachable marking tree of Petri nets to find the deadlock markings, and then,designing the controller of Petri net by combining the reason of the deadlock, toprevent and avoid deadlock. At the same time, how to design the controller ofPetri net with the uncontrollable transitions was discussed. In this paper, First ofall, the prohibiting constrains transform to the allowing constrains by equivalentlinear transformation. And then design a new mixed constrains. At last, designingthe controller make the Petri net live by the mixed constraints.In this paper, first of all, we propose a deadlock detection algorithm ofimproved reachable marking tree, resulting in a deadlock marking and a place ofa deadlock token. Afterward, we develop a new view of designing mixedconstrains. By using the developing reachable marking tree of Petri net to findthe deadlock markings and the places containing the deadlock markings, and thendesigning the mixed constrains of Petri net by combining the reason of deadlock.Finally, designing controller make the Petri net live by the mixed constrains., Atlast we solve the avoiding deadlock problem of the uncontrollable transitions inPetri net, using the constrain conversion algorithm of the equivalent lineartransformation construct a new mixed constrains to design the controller, makethe Petri net live.