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This study deals with the problem of dependence between production and failure rates in the context of a multi-product manufacturing system. It provides an answer about how to produce (i.e. the production rates) and what to produce (i.e. which product) over a finite horizon of H periods of equal length. We consider a single randomly failing and repairable manufacturing system producing two products Pa and Pb. The product Pa is produced to supply the strategic demand d(k) of the principal customer via a buffer stock S over k periods (k = 1, 2, ... , H). The second product Pb is produced to meet a secondary but very profitable demand. It is produced during a given interval at the end of each period k. We develop a genetic algorithm to determine simultaneously the optimal production rate of the first product during each period k and the optimal duration of the production interval of the second product, maximising the total expected profit. [ABSTRACT FROM AUTHOR]

This article, inspired by an industrial problem, develops efficient maintenance and just-in-time production policies in a subcontracting environment according to two orientations. The first invokes subcontracting with the objective of satisfying a constant customer demand knowing that our production system, composed of a machine M1, cannot satisfy the totality of demand. Subcontracting is represented by a machine M2 which has a constant failure rate, while three maintenance policies for M1 are tested and evaluated. The second orientation takes the perspective of our production system as a supplier which is obliged to allocate part of its production capacity to subcontracting so as to satisfy a constant demand. We consider a production system made up of two machines, both of which produce a single type of product, are subject to breakdowns and can carry out subcontracting tasks. The objective of this part of the article is to prove the efficiency of the so-called integrated maintenance policy, which combines production and maintenance decisions in a subcontracting environment. [ABSTRACT FROM AUTHOR]

In this paper, we deal with the problem of joint maintenance and production management under a subcontracting constraint. We will study a system with a machine M which undergoes corrective maintenance actions together with preventive maintenance actions, both of which have random durations. A stock S with a capacity h is developed at a rate α = Umax - d, where Umax = production rate, d = constant demand, and Umax > d. In addition, machine M is allocated to carry out subcontracting tasks (ST) at a frequency A1, for an effective duration A2, during which time it cannot be used to fulfil our system's demand d. We initially study the system analytically when the machine M is forced to carry out a single subcontracting task during each cycle T. We thereafter present a generalization of the subcontracting constraint which entails assigning the machine M to subcontracting several times during each cycle. [ABSTRACT FROM AUTHOR]

This paper investigates an integrated strategy of inventory control and preventive maintenance for a randomly failing production unit subject to a minimum required availability level. The production unit is submitted to a maintenance action as soon as it reaches a certain age m or at failure, whichever occurs first. A buffer stock h is built up at time A from the start of a production cycle in order to allow a continuous supply of the subsequent production unit at a constant rate during repair and preventive maintenance actions whose respective durations are random. A mathematical model and a numerical procedure are developed to find simultaneously the optimal values of the three decision variables (m*, h*, A*) which minimize the total average cost per time unit and satisfy the availability constraint. [ABSTRACT FROM AUTHOR]

A marked graph-based control synthesis method is proposed for discrete event systems. The proposed approach solves the forbidden state problems characterized by a set of General Mutual Exclusion Constraints (GMEC) and takes into account unobservable transitions. It exploits the structural dependence of places involved in GMEC constraints. For each case, analytical expression of the GMEC in its worst case, in terms of reachable marking, is given according to the observable firing sequence of the system. These constraints are then evaluated on-line by the supervisor. The proposed approach is illustrated on a real example. [ABSTRACT FROM AUTHOR]