Evaluation of operational policies in the design phase of material handling networks

We compare quality of solution and solution times of alternative operational dispatching policies that are integrated into the design phase of a material handling network for automated guided vehicle systems. Exact formulations describe the problem of optimal concurrent design of the unidirectional loop track layout along with the locations of the pickup and drop-off stations. The objective is to minimize the total loaded and empty vehicle trip distances, which is the main driver of the fleet size of the vehicles. A primary interest of our work is to illustrate the superiority of the shortest-trip-distance-first (STDF) over the first-come-first-served (FCFS) when integrated into the design phase. We also show that optimization under STDF in the design phase produces the best solution for first-encountered-first-served (FEFS) in the operation phase. The findings of the optimization models in the design phase are well supported by the outcomes of the simulation model in the operation phase.