Tesis doctoral de Liliana Capacho Betancourt
Nowadays assembly line balancing problems are commonly found in most industrial and manufacturing systems. Basically, these problems seek to assign a set of assembly tasks to an ordered sequence of workstations in such a way that precedence constraints are maintained a given efficiency measure( e.G. The number of workstations or the cycle time) is optimized. Because of the computational complexity of balancing problems research works traditionally considered numerous simplifying assumptions in which for example, a single model of a unique product were processed in a single line; moreover, problems were mainly restricted by precedence and cycle time constrains nevertheless, the current availability of computing resources and the enterprises need to adapt to rapid changes in production and manufacturing processes have encouraged researches and decision-makers to address more realistic problems. Some examples include problems that involve mixed models parallel workstations and parallel lines, multiple objectives and also further restrictions such a workstation processing capacity and resource allocation constraints. This doctoral thesis addresses a novel assembly line balancing problem entitled here asalbp, the alternative subgraphs assembly line balancing problem which considers alternative variants for different parts of an assembly or manufacturing process each variant can be represented by a precedence subgraph that establishes the tasks required to process a particular product their precedence requirements and their processing times. Therefore, to efficiently solve the alternative subgraphs assembly line balancing problem two subproblems need to be solved simultaneously(1) the decision problem that selects one assembly variant for each part that admit alternatives and(2) the balancing problem that assigns the tasks to the workstations. the analysis of the state-of-the-art carried out revealed that the alternative subgraphs assembly line balancing problem has not been addressed before in literature studies, which leaded to the characterization and definition of this new problem moreover, due to the impossibility of representing assembly variants in a standard precedence graph the s-graph is proposed here as a diagramming tool to represent all available assembly alternatives in a unique diagram habitually, problems involving assembly alternatives are solved by using a twestage based approach. In the initial stage, the system designer selects one of the possible le variants according to criteria such as total processing time once the assembly alternatives have been selected and a precedence graph is available (i.E. The assembly planning problem has been already solved, the line is then balanced in the second stage. However, by following this two-stage procedure it cannot be guaranteed that an optimal solution of the global problem can be obtained, because the decisions taken by the system designer restrict the problem and cause information loss i.E., A priori selection of an alternative leaves the effects of the other possibilities unexplored for instance, if the system designer uses total processing time as decision criterion the alternative with largest total processing time will be discarded notwithstanding it may provide the best solution of the problem (i.E., It requires the minimum numbers of workstations or minimum cycle time). Therefore, it seems reasonable to consider that to solve efficiently an albp that involves processing alternatives all possibilities must be considered with in the balancing process for this purpose, in this thesis both the variant selection problem and the balancing problem are jointly considered instead of independently different approaches are used here to address the alternative subgraphs assembly line balancing problem (asalbp).
Datos académicos de la tesis doctoral «Asalbp: the alternative subgraphs assembly line balancing problem formalization and resolution procedures.«
- Título de la tesis: Asalbp: the alternative subgraphs assembly line balancing problem formalization and resolution procedures.
- Autor: Liliana Capacho Betancourt
- Universidad: Politécnica de catalunya
- Fecha de lectura de la tesis: 29/02/2008
Dirección y tribunal
- Director de la tesis
- Rafael Pastor Moreno
- Tribunal
- Presidente del tribunal: albert Corominas subias
- manel Mateo doll (vocal)
- alexandre Dolgui (vocal)
- alexandre Dolgui (vocal)