Deadlock Prevention for Automated Manufacturing Systems with Uncontrollable and Unobservable Transitions: A Petri Net Approach

Deadlock Prevention for Automated Manufacturing Systems with Uncontrollable and Unobservable Transitions: A Petri Net Approach

Meng Qin (Xidian University, China)
Copyright: © 2013 |Pages: 21
DOI: 10.4018/978-1-4666-4034-4.ch015
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Abstract

Many deadlock prevention policies on the basis of Petri nets dealing with deadlock problems in flexible manufacturing systems exist. However, most of them do not consider uncontrollable and unobservable transitions. This chapter solves deadlock problems in Petri nets with uncontrollable and unobservable transitions. A sufficient condition is developed to decide whether an existing deadlock prevention policy is still applicable in a Petri net with uncontrollable and unobservable transitions, when the policy itself is developed under the assumption that all the transitions are controllable and observable. Moreover, the author develops a deadlock prevention policy to design liveness-enforcing supervisors for a class of Petri nets with partial observability and controllability of transitions. Furthermore, a sufficient condition to decide the existence of a monitor to enforce a liveness constraint is developed.
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2. Uncontrollable And Unobservable Transitions

Uncontrollable transitions are first proposed in automata (Ramadge & Wonham, 1989). Later, they are introduced into Petri nets (Giua et al., 1992). In this section, we give the definitions of uncontrollable and unobservable transitions.

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