Scheduling and Routing of AGVs for Large-scale Flexible Manufacturing Systems

In this paper, we propose a new heuristic as well as several improvements to an existing approach based on Benders decomposition for solving the conflict free scheduling and routing of automated guided vehicles (AGVs), with promising results. The existing method solves the problem in two stages; task assignment/sequencing, and feasibility check of the first stage’s solution subject to collision-avoidance constraints. The method is not suitable for large-scale AGV systems. We proposed several improvements and speedup strategies that result in fast methods capable of scheduling AGVs in a realistic layout with a graph of several hundred nodes and arcs. This is done by reformulating the mathematical model of the problem. We also introduce a new heuristic based on the improved method that yields high-quality solutions quickly. Moreover, we solve a real large-scale industrial instance by a commercial constraint programming solver and an open-source SMT solver. The results show that both of these general-purpose solvers can effectively solve our proposed models.