Design of Liveness-Enforcing Supervisors for FMSs Modeled by S<sup>4</sup>PR with Controllable Places and Transitions
Mowafak Hassan Abdul-Hussin
Abstract
This paper presents a liveness-enforcing supervisor synthesis technique for the Petri Net Model (PNM) of flexible manufacturing systems (FMSs). Particularly, the Petri net (PN) is an appropriate method to prevent deadlocks arising from FMS. We present a model of an S <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> PR as a general class of PN that can solve the deadlock handling of FMSs. An effective subclass of PN modeled by S <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> PR: systems of sequential systems with shared resources can be used to model many FMSs well. Siphons are given an effective tool to characterize deadlock (DL) situations and solve DL in PNs that model FMS. Two approaches are specified as PNs for the deadlock control to design monitors for siphons in S <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> PR-net. The first one has controlled methods by adding a proper control place (CP), and the second uses optimal control transitions (CTs). Besides, the specification supervisor leads to a liveness-enforcing PNs supervisor for behavior that is more permissive. These methods are verified by an FMS example, which could be modeled by an S <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> PR net, and is presented in a maximally permissive way.