In: International Journal of Intelligent Control Systems, Vol. 3, No. 3, pages 297-325. 1999.
Abstract: A rule-based methodology for the synthesis of Petri-net-based compiled supervisors for discrete event systems (DESs) is proposed to solve the forbidden state problem. The methodology proposed ensures that the size of the supervisor to be synthesized consists of a controlled automation Petri nets (APN) model of the system. In order to obtain the controlled APN model, the uncontrolled APN model which represents the uncontrolled behavior of the system and a set of token passing marking (TPM) rules are used. TPM rules are obtained by converting the forbidden state specifications into a set of related rules and they are implemented by using inhibitor and/or enabling arcs. APNs include the following extensions to the ordinary Petri net framework: sensor readings as firing conditions at transitions, and actions assigned to places. Ladder logic diagram code is used to implement the supervisor obtained. The applicability of this technique is demonstrated by considering a discrete manufacturing system.
Keywords: controlled Petri nets, forbidden states, rule-based, supervisory control.