DE solution for the earliness/tardiness case of Hybrid Flow-shop Scheduling problem with priority strategy

The earliness/tardiness (E/T) case of Hybrid Flow-shop Scheduling problem (HFSP) is an NP hard problem, which is difficult to deal with, however, the local assignment existing in the practical production increases the complexity of this problem. How to solve the combinatorial optimization problem effectively and optimally is still an open issue today. In this paper, differential evolution algorithm (DE) combined with priority strategy is used to solve this E/T scheduling problem. Firstly, DE algorithm is used to make global assignment and obtain each job´s process route. Secondly, the operating priority of the jobs in buffer area deduced from the expectation completion sequence is used to direct the local production assignment between stages, then the starting time of each job can be determined. Finally, under the constraints of the due-date, the global optimization with the minimal penalty sum of E/T is obtained. Several scheme comparisons with simulation results show the effectiveness of the proposed method.