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Analysis Of Siphon-Based Deadlock Prevention Polices For Flexible Manufacturing Systems

Posted on:2006-08-28Degree:MasterType:Thesis
Country:ChinaCandidate:W X CaoFull Text:PDF
GTID:2132360152971484Subject:Mechanical and electrical engineering
Abstract/Summary:PDF Full Text Request
The competition for limited resources can produce deadlocks in flexible manufacturing systems (FMS). Petri nets are an effective way to model, analyze, and control deadlocks in FMS. A variety of important Petri net-based methods to prevent deadlocks arising in FMS are to add some control places and related arcs to strict minimal siphons (SMS) such that no siphon can be emptied. Since the" number of siphons grows in general exponentially with respect to the size of a Petri net, their disadvantages lie in that they often add too many additional places to the net, thereby making the resulting net supervisor more complex than the originally built one. This thesis explores ways to minimize the new additions of places while achieving the same control purpose.Proposed by our previous work, elementary siphons are an efficient method to investigate the deadlock problems in Petri nets. An elementary siphon based deadlock prevention policy is developed in this thesis. Also this research presents an analysis to show the advantages of elementary siphons in the design of liveness-enforcing Petri net supervisors. By analyzing the deadlock control problems in some different scale FMS examples, we show that our policy always leads to structurally simple liveness-enforcing net supervisors. Moreover, the superiority of our approach can be clearly shown by large scale FMS.And in the process of investigation, we have a difficult problem of adding control places for many control places in the initial net. When we have a little mistake in the process of adding for our carelessness, we will get an unbelievable result. Hence, based on this problem, we put forward an algorithm to add arcs and develop a program for the initial net.
Keywords/Search Tags:Deadlock prevention, Elementary siphon, Flexible manufacturing systems, Petri nets
PDF Full Text Request
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