Scheduling research has mainly focused on development of efficient· algorithms for solving deterministic and single criterion models to overcome the associated computational time complexity. However, scheduling in practice, demands development of effective approaches in order to fill the gap between the theory and practice. As many other decision processes, scheduling usually involves imprecisely defined problem parameters and multiple conflicting criteria in real-life domains. This thesis aims to put forward novel methodologies for solving some real-life production scheduling problems. In particular two problems have been tackled that are faced in the production process of the collaborating establishment Denby Pottery Ltd: an integrated loading and scheduling problem of a batch processing kiln that is used to fire glazed products and scheduling of parallel flow-lines where products to be input to the firing kiln are glazed. The first problem concerns both short-term criteria of relevance to the shop-floor and criteria that are related to the longer term objectives of the firm. The short-term objectives, which are reduction of energy consumption and work-in-process inventories, can be modelled using crisp objective functions. The longer-term objectives of meeting financial targets of the firm and attaining balanced end-product inventory levels constitute imprecise goals to be achieved. Moreover, the relative importance of criteria is also iniprecisely defmed. A novel fuzzy goal programming method is developed for solving the kiln loading and scheduling problem. This method takes into account not only fuzzy goals but also fuzzy •importance relations among the goals. A new fuzzy goal programming model of the problem is built. A prototype decision support system is developed that involves this model as its model base. The effectiveness of the developed methodolo.gy in producing different non- .dominated solutions has been demonstrated. The second problem considers scheduling of a set ofjobs on parallel non-identical flow.~ ines with respect to sequence dependent set-ups, flow-line eligibilities and fuzzy due-dates. A hierarchical optimisation approach is proposed for solving the problem. In the first phase a s~redule maximising the minimum satisfaction degree with respect to the fuzzy due-dates is ·~ought. This is accomplished using a novel fuzzy mixed integer linear programming model :3f~~;problem. In the second phase further optimisation ofmachine utilisations is carried out '. ;Und~r co~sideration of the solutions obtained in the first phase using a secondary model. The .,c~.T~utational analysis of the models and their effectiveness in producing optimal solutions ''th~real-life instances ofthe problem are presented.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:492374 |
| Date | January 2007 |
| Creators | Akoz, Onur |
| Publisher | Coventry University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
Page generated in 0.0019 seconds