Unidirectional loop network layout problem in automated manufacturing systems

In this paper, we address the design of unidirectional loop network layouts for automated manufacturing environments. We show that the problem is NP-complete. Using a workstation interchange argument, we develop dominance relationships for easy identification of local optimal solutions. Our results suggest the need for simple heuristics to solve the problem. We identify cases in which the heuristics perform optimally, and we analyze the worst case behavior of the heuristics. We develop an optimal branch-and-bound procedure that is computationally efficient for medium-sized problems. We also present a decomposition principle helpful for dealing with large workflow matrices. We report computational results on the heuristics and the branch-and-bound procedure. We show that one of the heuristics performs impressively well in terms of solution quality and computational time requirements.