The unequal area facility layout problem with shortest single-loop AGV path: how material handling method matters

This paper studies an unequal area layout problem whose objective is to find a flexible bay layout with the best shortest single loop. The problem can be used for production systems in which material handling is carried out by automated guided vehicles (AGVs) that move along a single-loop path. The designed layout is robust against future changes in material flows, which are caused by different factors such as demand fluctuations, technology advancement, and new product introduction. It is first proved that there exists a feasible single loop for any bay layout, which indicates the problem is well-defined and always has a feasible solution. Then, a powerful hybrid algorithm based on Memetic and Simulated Annealing is developed. The algorithm is tested on many randomly generated instances and well-known instances from the literature. The numerical experiment shows that the proposed heuristic is both efficient and effective. The new layout-design approach significantly improves the loop-length when compared with the traditional approach in which the layout is first determined based on rectilinear distances, and then the best single loop is found. Our study highlights the importance of adequately incorporating the material handling system into the layout design phase.