Mathematical modeling and solution methods for worker -activity scheduling problems in a flexible manufacturing system environment

Resource flexibility has become interesting and challenging characteristic of scheduling problems. While on one side it reduces dependency on a particular resource for executing a job, on the other side it adds more complexity to getting good solutions. Most of studies on scheduling problems show that flexibility makes the already hard scheduling problems become even harder. It is shown in this work that the complexity of the scheduling problems with resource flexibility is due to network structure, the number of resources, and the number of activities. This work develops solution methods including exact and heuristic methods as well as a method to eliminate the sources of complexity of the problem. Surprisingly, the exact method is not only able to represent the problem under study but also different types of scheduling problems.;The experimental results with a moderate sized problem show that the performance of the solution methods is satisfactory with regard to the solution time and quality. The exact method is able to provide solution in an acceptable time while the heuristic method is able to provide solution very close to the optimal. The experimental results with larger sized problems reveal that the resource flexibility provides significant improvement to the schedule makespan. The value of this work is reflected in the implementation phase, where the developed method is used to solve a real scheduling problem faced by an aircraft manufacturer considering a fixed production rate. The results show that the method is able to provide a long-range production schedule with lower total overtime hours.