The synthesis and PLC implementation of hybrid modular supervisors for real time control of an experimental manufacturing system

In this paper, synthesis and PLC based implementation of hybrid modular supervisors for real time supervisory control of an experimental manufacturing system are proposed. The hybrid approach couples Ramadge-Wonham (RW) supervisors in the form of automata to uncontrolled PN models through inhibitor arcs. The RW supervisors can be obtained in monolithic or modular forms. In the monolithic case, there is only a single supervisor that has complex structure and huge number of states and events. The modularity of supervisors provides simple and small control structures compared to monolithic ones. Modular hybrid approach offers fewer states for the PLC implementation of the hybrid controller with less memory requirements. The applicability and effectiveness of the modular hybrid approach are demonstrated by the PLC based real-time control of an experimental manufacturing system for different cases. The obtained results show that modular supervisors require less memory space compared to monolithic counterparts. (C) 2014 The Society of Manufacturing Engineers. Published by Elsevier Ltd. All rights reserved.