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International audience; Ergonomics is a growing concerned in production systems. Companies aim to reduce work-related illnesses and the induced expenses (absenteeism, occupational accidents,...). The working conditions are mostly determined by the production system design, so this objective must be included early in the system design. The assignment of the tasks to the workstations plays a key role for ergonomics. The simple assembly line balancing problem (SALBP) is both one of the simplest and one of the most studied variants of this problem. In this work, we propose a solution method for the SALBP, introduced in [1], considering two objectives. The first one is related to the cost (by the number of stations) and the other is an ergonomic measure of the fatigue and recovery of operators. This last objective is based on the idea that the fatigue of the operator at the end of a cycle depends on the duration and difficulty of the tasks executed and on the recovery time. The method is an extension of the work presented in [2], integrating the ergonomic objective which is non-linear. Experimental results compare the performance of the bi-objective branch-and-bound to an epsilon-constraint.

International audience; Assembly lines are production systems designed for the final assembly of a manufacturing product, this mode of production is suitable for mass production, or mass customization.Assembly lines are composed of workstations connected between them with conveyors, semifinished products are transported in a constant speed (takt time) between the different workstations where the parts are added in sequence to form the final finished product. To maximize the profit, a cost-effective approach should be adopted to design assembly systems [6]. Optimization problems related to the design of the assembly systems are the combinatorial problem of assigning different tasks to workstations to assemble a product, denoted the Assembly Line Balancing Problem (ALBP) [3]. Moreover, in the design stage of assembly systems, a relevant problem is the equipment selection problem, when we select equipment to assign to different workstations in order to execute the different tasks, with the optimization of the design cost.The joint problem of equipment selection and line balancing will be referred to as the Assembly Line Design Problem (ALDP) [4].Due to the repetitive aspect of work in assembly lines, the manipulation of loads and heavy tools, industrial workers are exposed to work-related musculoskeletal disorders (MSDs). MSDs are the major source of disease and absenteeism among industrial workers, affecting the economics of the production system and resulting in high compensation and absenteeism costs with a decrease in the overall system productivity. Equipment to improve the efficiency of the work and/or the ergonomics of the workstation are costly. Hence, designers should consider the trade-off between the cost of equipment and their effects on ergonomics. There is a wide type of equipment to improve the work efficiency and ergonomics load, ranging from industrial lifts, tool balancers and mechanical manipulators up to new technological equipment such as augmented reality, collaborative robot (cobot) that interact with workers in a shared workspace and assistive exoskeleton technology.Advantages of considering ergonomics in the design stage are greater flexibility in balancing the workload and lower costs of interventions on existing lines. For designers, it is of primary importance to dispose of information on the trade-off between the investment and the ergonomics level ; the selection of equipment involves cost related to the purchase, the powering with electrical energy, air powering, cost of maintenance and worker’s training and formation. The expected level of ergonomics in the line is also of great importance since equipment could enhance the ergonomics but decrease the execution time, or vice-versa. Costly equipment comes with an improvement, either fastening the execution time, or decreasing the load of the execution of tasks, or both.

International audience; Dans un système de production, le processus de fabrication d’un produit est décomposé en tâches élémentaires, effectuées sur des stations de travail. La décision de la répartition de ces tâches sur les stations est un problème central de la conception des systèmes de production, puisqu’il détermine les caractéristiques de notre système de production, telles que le takt time(c’est-à-dire la cadence de la production), le nombre de stations (contribuant largement au coût), les conditions de travail des opérateurs... Les problèmes d’équilibrage de ligne d’assemblage consistent à déterminer cette répartition des tâches sur les stations, tout en respectant les contraintes de précédences entre les tâches. Parmi les nombreuses variantes des problèmes d’équilibrage de ligne [2], une des plus étudiée est le Simple Assembly Line Balancing Problem(SALBP) [6]. Ce problème considère une variante simple du problème d’équilibrage de ligne, dans lequel un seul type de produit est considéré, avec des temps opératoires pour chaque tâche déterministes et indépendants de la station sur laquelle les tâches sont effectuées. Les méthodes de résolution développées pour ce problème ont souvent servi de base pour des variantes plus complexes du problème d’équilibrage. Le SALBP est un problème NP-difficile [6]. Trois versions classiques du problème se retrouvent dans la littérature, différant par l’objectif optimisé :— SALBP-1 : minimise le nombre de stations, le takt time étant donné— SALBP-2 : minimise le takt time, le nombre de stations étant fixé— SALBP-E : minimise le produit du nombre de stations et du takt time.Les méthodes de résolutions exactes développées pour le résoudre sont généralement des algorithmes de branch-and-bound ou de programmation dynamique.

International audience

International audience; The aim of this paper is to provide a study of the existing methods and devices to be put into practice for the workplace analysis in terms of workload evaluation. In fact, the design of the workplace can impact on the physical fatigue and discomfort perceived by workers, resulting in the reduction of work quality and the increasing of tasks time. In addition, the repetition of activities which imply awkward postures with considerable impact on fatigue can lead in a long-term to a higher probability of injuries and to the reduction of workers capability in performing the activity. In this paper, we put in evidence how existing methods for workload evaluation can be applied both during the pre-design stage and for the improvement of the existing workplaces. The value of this work is to provide companies of an overall view of all the existing workload evaluations, developed formulations and devices to be used for predicting the impact of the tasks workload on operators and consequently on the system performance. This knowledge helps decision-makers in determining the most effective design-level decisions. Finally, some practical examples of pushing, pulling and carrying activities evaluation are given putting in evidence the output that such devices can give to a practitioner.