Optimal Dynamic Behavior of Adaptive WIP Regulation with Multiple Modes of Capacity Adjustment

It is desirable to maintain consistent dynamic behavior of WIP regulation in work systems with multiple modes of capacity adjustment (floaters, overtime, etc.) and different adjustment periods, delays and limits in the various modes. Coordination of these modes is necessary in order to keep optimal dynamic behavior. In this paper, a control-theoretic model of WIP regulation is presented first that accommodates multiple capacity adjustment modes with different adjustment periods (per shift, per day, per week, etc.) and different delays in implementing adjustments. Then an algorithm is presented for adapting WIP adjustment parameters in the presence of capacity adjustment limits and mode priorities so that a specified dynamic performance goal continues to be met. Results of simulations driven by industrial data are used to illustrate the effect of limits and performance goals on dynamic behavior, and conclusions are drawn regarding the effectiveness of adaptive regulation of WIP by coordinating multiple modes of capacity adjustment.