Zhou YIdong
M.S. |
Iterative algorithms for batching and scheduling to minimize the total tardiness in two-stage hybrid flow shops This study addresses loading and scheduling for flexible manufacturing systems with controllable processing times, i.e. processing times are not given, but can be changed according to energy consumption, precision levels, scheduling performances, and so on. For given set of parts to be produced during the upcoming period, the problem is to determine the allocation of operations and their cutting tools to machines, the operation processing times, and the sequence of the parts to be processed on each machine for the objective of minimizing the sum of operation processing costs and weighted tardiness. Some practical considerations such as tool lives, tool copies and tool sharing are also incorporated into the problem. A mixed integer programming model is developed to represent the problem mathematically. Then, an iterative solution approach is proposed that solves the two sub-problems repeatedly until no more improvement can be obtained, where the loading sub-problem is solved by a modified bin packing algorithm under given initial operation processing times and the resulting scheduling sub-problem is solved by the priority scheduling approach while changing the initial operation processing times. To test the performance of the iterative solution approach, computational experiments were done on various test instances, and the results are reported. |
