Journées de l'optimisation 2007 Optimizations days

Une méthode analytique pour évaluer les performances d’une ligne de production composée de stocks intermédiaires et de machines réparables pouvant avoir deux modes de défaillances, est proposée. Chacun de ces modes est caractérisé par ses propres temps de bon fonctionnement et de réparation qui sont des variables aléatoires exponentiellement distribuées. Un modèle continu est utilisé pour décrire le débit d’une machine ou le niveau d’un stock. La méthode procède par agrégation de machines. L’approche proposée est validée par simulation.

In this paper we study multi-product lot streaming problems in a flow shop by considering capacitated buffer size and capacitated material handling equipment between production stages. The problem involves splitting given order quantities of different products into sublots and determining their optimal sequence. Lot streaming problems with equal, consistent and variable sublot sizes are studied. Moreover, problems with and without machine intermittent idling, job waiting and job pre-emitting are investigated.

This presentation introduces a hybrid optimization approach to solve the multi-state system (MSS) expansion scheduling problem. MSS availability modeling considers that a system and its elements may experience a range of performance levels from perfect functioning to complete failure. The system study horizon is divided into several periods. At each period the demand distribution is predicted in the form of a cumulative demand curve. The system consists of several components connected in series. Redundant elements are included in order to achieve a desirable level of production availability. Each element is characterized by its capacity or its productivity, its availability and its cost. For example, these elements can represent machines in a manufacturing system or electric generating devices in a power system. The proposed heuristic determines the minimal investment-cost over the study period under availability constraints. An originality of our approach is that it proceeds by dividing the search space into a set of disjoint subsets, and then uses a combination of genetic algorithm and tabu search approach. Numerical results for test problem from previous research are reported and compared. The results show the advantages of our hybrid algorithm for solving this type of problem.