In: International Journal for Advanced Manufacturing Technologies, Vol. 16, No. 7, pages 498-515. 2000.
Abstract: A new Petri net based design technique, called the inhibitor arc method, for the synthesis of compiled supervisors for discrete event systems is used to solve the forbidden state problem in an experimental manufacturing system. The synthesized supervisors consist of a controlled automation Petri net model of the system. Automation Petri nets include the following extensions of the ordinary Petri net framework: sensor readings as firing conditions at transitions and actions assigned to places. The ladder logic diagram code is used to implement the supervisors on programmable logic controllers. The obtained supervisors are correct by construction, therefore there is no need for verification. The paper shows the applicability of the previous results of Jones at al. (1998) to low-level real-time control where the role of the supervisor is to arrange the low-level interactions between the control devices, such as motors, actuators, etc. This is done by considering an experimental manufacturing system.
Keywords: Petri nets, forbidden states, inhibitor arcs, real-time systems, supervisory systems.