PROMETHEE: A comprehensive literature review on methodologies and applications

A survey on problems and methods in generalized assembly line balancing

State-of-the-art exact and heuristic solution procedures for simple assembly line balancing

A classification of assembly line balancing problems

Assembly lines are special flow-line production systems which are of great importance in the indus-trial production of high quantity standardized commodities. Recently, assembly lines even gained importance in low volume production of customized products (mass-customization). Due to high capital requirements when installing or redesigning a line, its configuration planning is of great rele-vance for practitioners. Accordingly, this attracted attention of plenty researchers, who tried to sup-port real-world configuration planning by suited optimization models (assembly line balancing prob-lems). In spite of the enormous academic effort in assembly line balancing, there remains a consider-able gap between requirements of real configuration problems and the status of research. To ease communication between researchers and practitioners, we provide a classification scheme of assem-bly line balancing. This is a valuable step in identifying remaining research challenges which might contribute to closing the gap.

The purpose of this paper is to describe the main problems concerning the design and operation of mixed-product assembly lines. We will focus on the design of assembly lines, which is most of the time composed in three steps. The first is the elaboration of the logical layout of the line, which consists in the distribution of operations among workstations along the line. The second is the choice of the most efficient product mix and production sequence in relation to the operation phase. The third is the subsequent elaboration of the physical layout of the line, i.e., deciding about the disposition of the workstations, conveyor(s), possible buffers, etc., on the shop floor. In this paper, the accent will be put exclusively on the first two steps. The concept of balance for ordering (BFO) is introduced to solve these two interrelated problems. After an overview of the current work in this area, this paper presents in detail a very promising approach to solve the BFO: the grouping and ordering genetic algorithms (genetic algorithms heavily modified to solve grouping/ordering problems). In all cases, the main concern is the quality of the resulting line in terms of cost and its suitability to the line designer's needs (special user preferences are followed as closely as possible). Academic and experimental results are presented, and they confirm the efficiency of the proposed approaches.

Designing mixed-product assembly lines

The layout problem arises in a production plant during the study of a new production system, but also during a possible restructuring. The main aim of layout design is to reduce transportation and maintenance, which simplifies management, shortens lead time, improves product quality and speeds up the response to market fluctuations. A principle of Group Technology (GT) advocates the division of a unity into small groups or cells. As it is most of the time impossible to design totally independent cells, the problem is to minimise traffic of items between the cells, for a fixed maximum cell size. This problem is known as cell formation problem (CFP). We propose here an original approach to solve this NP-hard problem. It is based on a Grouping Genetic Algorithm (GGA), a special class of genetic algorithms, heavily modified to suit the structure of grouping problems. The crucial advantage of this GGA is that it is able to deal with large instances of the problem thus becoming a powerful tool for an engineer determining a plant layout, allowing him or her to try several plant options, without the limitation of huge computation times.

Grouping genetic algorithms: an efficient method to solve the cell formation problem

The paper describes a new method to deal with the hybrid assembly line design, taking multiple objectives into account. It aims to assign a set of tasks to stations and to select the resources to perform each of them, while minimizing the total cost of the line and integrating design and operation issues. A grouping genetic algorithm was developed to solve the problem, hybridized with a branch-and-cut algorithm and the multicriteria decision-aid method PROMETHEE II. The study presents the method used for the allotment of tasks to stations and the determination of the assembly equipment used for each operation. It also introduces a manner to take into account user's preferences 'transparently' in multiple objectives' design problems. The essential concepts adopted in this approach are described and the application of the algorithm to an industrial case study is presented.

Hybrid assembly line design and user's preferences

The equal piles problem applied to assembly lines seeks to assign assembly tasks to a fixed number of workstations in such a way that the workload on each station is nearly equal. We present a new algorithm to treat this special application of the assembly line balancing problem. The algorithm uses a grouping genetic algorithm (GCA), based on an equal piles approach, and heavily modified with respect the precedence constraints between operations. The main concern is the quality of the resulting line in terms of balancing, and its suitability to the user's preferences. The essential and distinct concepts adopted by the method are described along with its step-by-step execution procedure and an illustrative example.

Applying the equal piles problem to balance assembly lines

The aim of the research presented in this paper was to propose a simple and cheap system, able to produce a macroscopic (centimetric) travel with a very high (nano-metric) resolution. The solution principle described yields a theoretically infinite travel range based on the accumulation of successive steps. The travel range of the prototype realised is equal to 2 cm , the size of the steps being about 20 nm . The actuation is based on the stick–slip effect: during the first stage of a step, the legs of the actuator slowly translate the carried structure; in the second stage the legs are moved back in their initial position very quickly, so that, thanks to their inertia, the structure stays at the same place. Each leg of the system, glued on a main frame, consists in a piezoelectric device working in shear mode, ended by a ruby hemisphere. The structure itself is in steel to get a sufficiently high inertia. An originality of the proposed translator is that the guiding elements of the structure (guiding grooves) are also used to transmit the motion. The friction force between the legs and the grooves can be tuned thanks to a magnet placed in the main frame, allowing to adjust the normal load on the legs. The paper presents the different functional elements of the translator and its electronic command system, and explains its functioning. The influence of several parameters (supported load, friction, resistive axial load) on the step size and thus on both the resolution, hence the speed of the system is then studied. Finally, the power losses are identified and estimated.

P. De Lit

Papers

Designing mixed-product assembly lines

Grouping genetic algorithms: an efficient method to solve the cell formation problem

Hybrid assembly line design and user's preferences

Applying the equal piles problem to balance assembly lines

Design and performances of a one-degree-of-freedom guided nano-actuator