Integrating Petri Nets and hybrid heuristic search for the scheduling of FMS

Abstract

This paper studies modelling and scheduling of Flexible Manufacturing Systems (FMS) using Petri Nets (PNs) and Artificial Intelligence (AI) based on heuristic search methods. A subclass of PNs, Buffer nets or B-nets is obtained by the systematic synthesis of PN models from FMS formulations. Scheduling is performed as heuristic search in the reachability tree, which is guided by a new heuristic function that exploits PN information. This heuristic is derived from a new concept, the Resource Cost Reachability (RCR) matrix which builds on the properties of B-nets. To mitigate the complexity problem, a hybrid search algorithm is proposed. The algorithm combines dispatching rules based on analysis information provided by the PN simulation with a modified stage-search algorithm. Experimental results are provided and indicate the effectiveness of the approach and the potential of PN-based heuristic search for FMS scheduling.