Design, analysis and implementation of a real-world manufacturing cell controller based on Petri nets

摘要

The primary function of a flexible manufacturing cell controller is to coordinate equipment within a cell to perform a sequence of manufacturing operations required by flexible production. In this paper, we present the modelling, analysis and implementation of a real-world cell controller. A Petri net-based development environment for cell controller design and implementation is described. The intended advantage of the proposed environment is that, users can define and/or change operation flow directly on the modelled Petri net, without programming efforts, otherwise required for general cell controller implementation. The proposed environment is used to design and implement a real-world flexible manufacturing cell controller at National Taiwan University of Science and Technology (NTUST). A scenario-based approach is adopted to model the operation flows in the cell, and from the scenario, we construct its Petri net model. To our knowledge, this is the first work that formalizes the conversion of scenarios to Petri nets. The resultant net is an augmented marked graph (Chu and Xie, 1997, IEEE Trans. Robotics Automat., 13(6), 793 - 804), whose liveness and reversibility are related to empty siphons. For qualitative analysis, after we reduce the net, we are able to generate all minimal siphons and traps, and show that the cell model is live and reversible.