An Improved Convex Optimization Model for Two-Dimensional Facility Layout

Abstract

The facility layout design problem is a fundamental optimization problem encountered in many manufacturing and service organizations that was originally formulated in 1963 by Armour & Buffa. This thesis derives a convex programming model, IBIMODEL, that is designed to improve upon the ModCoAR model of Anjos & Vannelli for the facility layout problem with unequal areas. The purpose of IBIMODEL is to find 'good' initial locations for the departments that a second model then uses to produce a detailed solution to the facility layout problem. The proposed model has four ideas behind it: unlike ModCoAR, it does not improve the objective function as the departments start overlapping, it takes into account the aspect ratio requirements, it introduces a systematic approach to making parameter choices, and it uses a new second stage recently proposed by Luo, Anjos & Vannelli to obtain the actual facility layouts. In this way, IBIMODEL efficiently generates a reasonably diverse set of superior solutions that allow the second stage to provide a wide variety of layouts with relatively low aspect ratios and total cost.

The proposed methodology was implemented and numerical results are presented on well-known large layout problems from the literature. To demonstrate the potential of the combination of IBIMODEL with Luo, Anjos & Vannelli's model, our results are compared with the best layouts found to date for these well-known large facility layout problems. The results support the conclusion that the propose a methodology consistently produces competitive, and often improved, layouts for large instances when compared with other approaches in the literature.