Genetic search for facility layout design under interflows uncertainty

We introduce the concept of fuzzy interflow into the facility layout design problem. We address the fuzzy facility layout problem where the uncertainty of material flows among facilities is represented as trapezoidal fuzzy numbers. Genetic algorithms are applied to such a hard fuzzy combinatorial problem. Polish expression is adopted as the coding scheme of chromosomes. The condition of legality for Polish expression coding and the condition for the searching cut point in a chromosome are given. Based on these conditions, an effective initialization procedure and layout construction procedure are built. The fuzzy ranking method is used to select the best layout in fuzzy context. A penalty to the violation of aspect ratio for each facility is used to guide genetic search effectively towards the promising part of the solution space. The possibility theory and fuzzy integral are used to meaningfully interpret the fuzzy results. The simulation results demonstrate that the genetic algorithm and fuzzy approach can be efficient tools to solve large-scale layout problems