Optimal Firing Sequence Problem Research Articles

Petri Net Decomposition Approach for Dispatching and Conflict-Free Routing of Bidirectional Automated Guided Vehicle Systems

In this paper, we address a Petri net decomposition approach for simultaneous dispatching and conflict-free routing for bidirectional automated guided vehicle (AGV) systems in dynamic environments. To solve the dynamic problem, static problems for finding near-optimal dispatching and conflict-free routing are solved each time when transportation requests are given. The static problem is converted to an optimal firing sequence problem for a timed Petri net. A Petri net decomposition approach is applied to solve the problem efficiently. In the algorithm, the entire Petri net is decomposed into task and AGV subnets. The penalty function method is used to derive a solution for all subnets. A deadlock avoidance method is embedded in the proposed methodology to ensure the feasibility and the quality of the solution. Computational results show that the proposed method with a deadlock avoidance algorithm efficiently maximizes the throughput for dynamic situations.

Petri Net Decomposition Approach for Bi-Objective Routing for AGV Systems Minimizing Total Traveling Time and Equalizing Delivery Time

In this paper, we propose Petri net decomposition approach for bi-objective optimization of conflict-free routing for AGV systems. The objective is minimizing total traveling time and equalizing delivery time simultaneously. The dispatching and conflict-free routing problem for AGVs is represented as a bi-objective optimal firing sequence problem for Petri Net. A Petri net decomposition approach is proposed to solve the bi-objective optimization problem efficiently. The convergence of the proposed algorithm is improved reducing search region by the proposed coordination method. The effectiveness of the proposed method is compared with that of a nearest neighborhood dispatching method. Computational results are provided to show the effectiveness of the proposed method.