Search

We present a new control scheme for releasing parts into a flexible manufacturing system (FMS) that is based on incremental optimization. Our objective is to exploit the available routing flexibility of parts in an enhanced manner by viewing part release as an assignment problem using system status information. In particular, we propose an “intelligent” part release mechanism with some look-ahead and optimization features in order to allow for optimization-based “cooperation” of workcenters. The cooperative dispatching concept is implemented in an object-oriented computer simulation model, and experiments with a varying degree of average routing flexibility are performed. The experimental results are used for a statistical analysis of the benefits of cooperative dispatching versus the common approach of standard dispatching. Finally, we investigate the robustness of the presented FMS control scheme in the case of random machine breakdowns.

Score orienteering is a variant of the orienteering game where competitors start at a specified control point, visit as many control points as possible and thereby collect prizes, and return to the starting point within a prescribed amount of time. The competitor with the highest amount of prizes wins the game. In this paper, we propose the minimum directed 1-subtree problem as a new relaxation to this problem and develop two methods to improve its lower bound. We describe a cut and dual simplex method and a Lagrangian relaxation method, and construct an algorithm that combines these two methods in an appropriate way. Computational experiments are carried out to analyse the behavior of the proposed relaxation with respect to the characteristics of the test problems. Especially for large-scale instances, we find that the proposed relaxation is superior to the ordinary assignment relaxation.