Hybrid optimization approach for layout design of unequal-area facilities

A hybrid optimization approach is presented for the layout design of unequal-area facilities. Simulated annealing is used to optimize a randomly generated initial placement on an `extended plane' considering the unequal-area facilities enclosed in magnified envelop blocks. An analytical method is then applied to obtain the optimum placement of each envelop block in the direction of steepest descent. Stepwise reduction of the sizes of the envelop blocks allows controlled convergence in a multi-phase optimization process. The presented test problems include two large size benchmark problems of 50 and 100 facilities of unequal areas. The results indicate that although the computational cost is relatively quite high, the technique is a significant improvement over previously published techniques for unequal-area facilities and can yield solutions of the same quality as obtained by PLANOPT, a general-purpose layout optimization program based on pseudo-exhaustive search.