Petri net based hierarchical and distributed implementation of robotic manufacturing systems

In this paper, based on discrete event driven systems, a method of representing cooperative behavior of multiple robots and machines in robotic manufacturing systems using Petri nets is presented. By decomposing a discrete event process into conditions, events and their interrelations with special purpose communication functions for real-time control of machines, extended Petri net models of robotic processes and behaviors are efficiently defined. Simulation and control is realized through client-server communication between several local controllers and one system controller. Implementation of hierarchical and distributed control is described for an example multi-robot manufacturing system. Fundamental experiments confirmed that the proposed system can be used as an effective tool for consistent modeling and control of large and complex manufacturing systems.