Integrated Maintenance and Service Policies Definition for Urban Ropeway Transport System

International audienceThis work proposes a stochastic model for integrating service and maintenance policies in order to address the queuing problem and the cost of maintenance for public transport systems. The authors adopt the following approaches: (i) a cost-model that considers the uncertainty of passengers’ plans to compute the waiting time; (ii) a maintenance cost-model which take into account two different maintenance policies (periodic block-type and age-based); and (iii) a bi-objective optimisation process to bring together the service and maintenance policies. Finally, the proposed work is applied to a massive-urban ropeway belonging to a public transportation system, in which the current service policy has been evaluated, considering the established transportation operation

Optimization of Two-Level Disassembly/Remanufacturing/Assembly System with an Integrated Maintenance Strategy

International audienceWith an increase of environmental pressure on economic activities, reverse flow is increasingly important. It seeks to save resources, eliminate waste, and improve productivity. This paper investigates the optimization of the disassembly, remanufacturing and assembly system, taking into account assembly-disassembly system degradation. An analytical model is developed to consider disassembly, remanufacturing of used/end-of-life product and assembly of the finished product. The finished product is composed of remanufactured and new components. A maintenance policy is sequentially integrated to reduce the system unavailability. The aim of this study is to help decision-makers, under certain conditions, choose the most cost-effective process for them to satisfy the customer as well as to adapt to the potential risk that can perturb the disassembly-assembly system. A heuristic is developed to determine the optimal ordered date of the used end-of-life product as well as the optimum release dates of new external components. The results reveal that considering some remanufacturing and purchase components costs, the proposed model is more economical in comparison with a model without remanufactured parts. Numerical results are provided to illustrate the impact of the variation of the ordering cost and quality of the used end-of-life product on the system profitability. Finally, the risk due to system repair periods is discussed, which has an impact on managerial decision-making

Optimal integrated maintenance/production policy for randomly failing systems with variable failure rate

International audienceThis article deals with the combined production and maintenance plans for a manufacturing system satisfying a random demand. We first establish an optimal production plan which minimises the average total inventory and production cost. Second, using this optimal production plan, and taking into account the deterioration of the machine according to its production rate, we derive an optimal maintenance schedule which minimises the maintenance cost. A numerical example illustrates the proposed approach, this analytical approach, based on a stochastic optimisation model and using the operational age concept, reveals the significant influence of the production rate on the deterioration of the manufacturing system and consequently on the integrated production/maintenance policy

Geometric Approach and Taboo Search for Scheduling Flexible Manufacturing Systems

This paper addresses the scheduling and deadlock avoidance of a class of automated manufacturing systems. In such systems, a set of jobs is to be performed on a set of resources and each job requires several operations- . An operation may require several types of resources with several units of each type. Further, upon the completion of an operation, its related resources cannot be released until resources needed for the next operation become available. One important characteristic of such systems is the possibility of deadlock. The scheduling problem deals with the allocation of resources such that jobs are completed within a minimal makespan and deadlocks are avoided. We extend the classical geometric approach to solve the two­job case of our model. A greedy algorithm based on this result and the taboo search heuristic is then developed for the general case. Numerical results show that the proposed algorithm is fast and provides good schedules

No-wait scheduling of a two-machine flow-shop to minimize the makespan under non-availability constraints and different release dates

International audienceIn this paper, we consider the two-machine no-wait flow-shop scheduling problem, when every machine is subject to one non-availability constraint and jobs have different release dates. The non-availability intervals of the machines overlap and they are known in advance. We aim to find a non-resumable schedule that minimises the makespan. We propose several lower bounds and upper bounds. These bounding procedures are used in a branch-and-bound algorithm. Computational experiments are carried out on a large set of instances and the obtained results show the effectiveness of our method

Maintenance strategy for lease equipment

International audienceIn case of leasing, the user rents equipment for a predetermined time. During this period, all maintenance actions are performed by the lessor. In this research paper, the aim consists to determine an optimal maintenance policy for ensuring a minimum reliability, required by the customer. Two strategies are proposed: the first consists to perform preventive actions whenever the system reliability reaches a predefined reliability threshold. These actions are characterized by a reduction of the system age. The objective is therefore to determine the efficiency factor of the optimal maintenance minimizing maintenance costs. For the second strategy, "improvement” actions replace the corrective actions during an interval to be determined to minimize maintenance costs. The first strategy will be solved using a numerical procedure and the second strategy uses an algorithm of discrete event simulation

Chapter 11 - Intelligent integrated maintenance policies for manufacturing systems

Artificial tntelligence techniques for networked manufacturing enterprises management, ISBN: 978-1-84996-118-9 (in press)International audienceNowadays, the fierce competition between enterprises has led many of them to revise their maintenance and production or service strategies. Satisfying customer demand in a timely fashion has become difficult due to the demand's random nature, a problem compounded by machine failures and low system availability. Much of the literature addressing this situation describes models and methods to optimize maintenance policies. By contrast, the research presented in this chapter is geared toward the development of a set of intelligent maintenance policies, which optimize integrated maintenance, inventory and production elements while satisfying random demand over future periods. This is a complex task due to the various uncertainties involved, which are due to external or internal factors. For instance, the variations in the environmental and operational conditions can be considered as external factors whereas the variations in the material availability can be considered as internal factors. The approach described in this chapter demonstrates the significant influence these factors have on the system failure rate, which is in turn important in the determination of an optimal intelligent maintenance strategy. We also emphasize that, on the one hand, high machine availability is an underlying assumption of just-in-time production control policies, and on the other hand, the traditional approach, which dissociates maintenance and production, is no longer satisfactory

An integrated production planning model for molds and end items

International audienceThis study develops a mathematical modelling framework for simultaneously generating production plans for molds and the end items that are made with them. The inputs considered are the item demand (assumed constant over an infinite planning horizon), holding costs and shortage costs, together with the molds' statistical lifetime distribution (in terms of number of uses) and costs pertaining to amortization, preventive replacements and corrective replacements