Solution Strategy of Integrated Optimization of Production Planning and Scheduling in a Flexible Job-shop

Abstract

To cope with the interaction between production planning and scheduling in a flexible job shop(FJS),an integrated optimization model for production planning and scheduling is presented.Safety stock,demand loss and flexible process routing of jobs are involved in the model.A decomposition algorithm based on Lagrangian relaxation(LR) is used to solve this model,and the integrated problem is decomposed into a production planning sub-problem and a flexible scheduling sub-problem.For the relaxed production planning sub-problem,a new cost structure is provided in order to make the decision-making coincide with the practical problem,and an algorithm which combines varying fix-and-relax with rolling-horizon is developed to solve the planning sub-problem.For the flexible process routing of the scheduling sub-problem,a new strategy of machine assignment is addressed.Numerical experiments validate the efectiveness of the proposed model and algorithm.