An Enhanced Supervisory Control Strategy for Periodicity Mutual Exclusions in Discrete Event Systems Based on Petri Nets

Abstract

Mutual exclusion problems widely exist in discrete event systems in which several processes will compete for the common resource for maintaining their normal running. This competition is mutually exclusive. However, a special behavior, that is, periodic mutual exclusion behavior, is important for many discrete event systems. Once a process obtains the common resource, it will consecutively obtain the common resource in the following several competitions. The other processes should wait for the release of the common resource. All processes will compete for the common resource again after the common resource is released. These competitions have obvious periodicity. In this paper, a methodology is proposed to design periodic mutual exclusion supervisors to control the periodic mutual exclusion behavior in discrete event systems. Moreover, two original structural conversion concepts, called -derivation and -convergence processes, are proposed to construct the periodic mutual exclusion supervisors. The discussion results show that many undesirable execution sequences are forbidden since the periodic mutual exclusion behavior is controlled by the proposed periodic mutual exclusion supervisors. Finally, an example is used to illustrate the proposed methodology.

A Multistep Look-Ahead Deadlock Avoidance Policy for Automated Manufacturing Systems

“…Each of the places 13 and 21 has one token. Initial tokens in 14 , 15 , and 17 -20 can be variable to explore the relationship between the steps and their initial markings. Let each of them first contain only one token, respectively.…”

“…They become a popular mathematical formalism to deal with deadlock problems in discrete event systems [9,10] as well as scheduling and supervisory control [11][12][13][14][15][16][17][18]. To manage the problem of deadlocks in a system, three methods have been developed by researchers and practitioners.…”