Scheduling of Flexible Manufacturing Systems Based on Place-Timed Petri Nets and Basis Reachability Graphs

TL;DR

This paper introduces an efficient scheduling method for flexible manufacturing systems using place-timed Petri nets and basis reachability graphs, significantly improving search efficiency and solution quality for large systems.

Contribution

It develops an improved beam search algorithm utilizing a compact basis reachability graph to optimize scheduling in large flexible manufacturing systems.

Findings

Enhanced search efficiency over existing methods

Maintains high solution quality in scheduling

Effective for large-scale manufacturing systems

Abstract

Scheduling is a key decision-making process to improve the performance of flexible manufacturing systems. Place-timed Petri nets provide a formal method for graphically modeling and analyzing such systems. By generating reachability graphs and combining intelligent search algorithms, operation sequences from the initial state to the target state can be found for the underlying system. However, the reachability graph grows exponentially with the system size increases, which is the main challenge of existing methods for scheduling large systems. To this end, we develop an efficient improved beam search algorithm to optimize the makespan based on a compact representation of reachability graph called basis reachability graph. The key idea behind the proposed method is to form a state together with the basis markings and its corresponding transition sequences, and evaluate the cost of the state based on the resource idle time. Experimental results are conducted on several benchmark systems which show that the developed method improves the search efficiency while ensuring the quality of the solution compared with existing methods.