Design of Liveness-Enforcing Supervisors for Flexible Manufacturing Systems Using Petri Nets

• Published in: IEEE transactions on systems, man and cybernetics. Part C, Applications and reviews Vol. 37; no. 4; pp. 517 - 526
• Main Authors: Li, Zhi Wu, Hu, He Suan, Wang, An Rong
• Format: Journal Article
• Language: English
• Published: IEEE 01.07.2007
• Subjects: C (programming language); Control systems; Deadlock prevention; elementary siphon; Enumeration; flexible manufacturing system (FMS); Flexible manufacturing systems; Linear programming; Manufacturing systems; Mathematical models; Monitoring; Monitors; Partial response channels; Petri net; Petri nets; Power system modeling; Siphons; Supervisors; System recovery
• ISSN: 1094-6977; 1558-2442
• DOI: 10.1109/TSMCC.2007.897333

This correspondence develops a methodology to synthesize supervisors for a special class of Petri nets that can well model many flexible manufacturing systems. In our previous work, siphons in a Petri net are divided into elementary and dependent ones on the condition that all emptiable minimal siphons are computed. In this research, a mixed integer programming (MlP)-based deadlock detection technique is used to find some, in general not all, minimal siphons in a plant model without complete siphon enumeration. For each siphon found, depending on its noncontrollability, a monitor is added such that it is invariant-controlled. Our siphon control method guarantees that no emptiable control-induced siphon is generated due to the addition of the monitors. The siphon control process proceeds iteratively until there is no unmarked siphon in the supervisor of a plant model. Compared with the existing approaches, the novel deadlock prevention policy can usually lead to a structurally simple liveness-enforcing supervisor by adding only a small number of monitors and arcs. More importantly, complete siphon enumeration is avoided. A practical flexible manufacturing system (FMS) example is utilized to illustrate the proposed methods.