A hierarchical weight assignment model in hierarchical production planning

Abstract

In this study, a linear programming model is developed which integrates aggregate planning and scheduling systems in a hierarchical planning system of a tire manufacturer. In the hierarchical planning system, medium-term production plans are formed initially by using an aggregate production planning system. According to those plans, schedules are made in which short-term operational decisions are made by using of scheduling system. In this planning process, schedules should be revised because of changing status in shop-floor or fluctuations in demand. However, the system may fall short of the optimal solution that is found with aggregate plans when revision is made only in the schedules. At this point aggregate production planning and scheduling system should be integrated in addition schedules and medium-term production plans revised simultaneously. The proposed extended aggregate planning model aims to coordinate that integration simultaneously. Since the proposed model has a multi-criteria objective function with many competing objectives, it is hard to manage the results of linear programming model. In this study, a second mathematical model, which is hierarchical weight assignment model, is proposed to solve this problem. The proposed model includes comparison matrices which are similar with the matrix form in the analytic hierarchy processes to make optimal aggregate plans according to the planner’s preferences in customer and product priorities. Finally, the calculated weights from the hierarchical weight assignment model are integrated to the capacity planning (CP) model in the hierarchical planning system of tire manufacturer and the proposed model is tested in order to visualize the performance.