Improved net rewriting system-based approach to model reconfiguration of reconfigurable manufacturing systems

摘要

This work aims at presenting a method for rapidly reconfiguring Petri net (PN) models of reconfigurable manufacturing systems (RMS). We start with introducing the model of improved net rewriting systems (INRS), which supports dynamic structural changes in a PN model without losing its important behavioral properties, i.e., liveness, boundedness (or safeness), and reversibility. Based on INRS, the method for rapid reconfiguration of Petri net models for RMS is proposed and an implementation algorithm is designed as well. In our method, changes in a RMS configuration adjusted with production demands can be rapidly formalized into graph rewriting rules of an INRS called model reconfigurator whose underlying Petri net is the existing Petri net model. Subsequently, by applying these rewriting rules, the existing Petri net model can be reconfigured rapidly into a new one for the RMS with a new configuration. Validity of the resulting Petri net model can be guaranteed naturally throughout the whole reconfiguration process and thereby there is no need for verification. A case study is provided that demonstrates the reconfiguration process of a Petri net model for a reconfigurable manufacturing cell. The given case study shows that the proposed method is capable for reconfiguring PN models of RMS in a rapid and successive manner, without requiring verification.