Stabilized-Cycle Strategy for Capacitated Lot Sizing with Multiple Products: Fill-Rate Constraints in Rolling Schedules

摘要

In practice, deterministic, multi-period lot-sizing models are implemented in rolling schedules since this allows the revision of decisions beyond the frozen horizon. Thus, rolling schedules are able to take realizations and updated forecasts of uncertain data (e.g., customer demands) into account. Furthermore, it is common to hold safety stocks to ensure given service levels (e.g., fill rate). As we will show, this approach, implemented in rolling schedules, often results in increased setup and holding costs while (over-)accomplishing given fill rates. A well-known alternative to deterministic planning models are stochastic, static, multi-period planning models used in the static uncertainty strategy, which results in stable plans. However, these models have a lack of flexibility to react to the realization of uncertain data. As a result, actual costs may differ widely from planned costs, and downside deviations of actual fill rates from those given are very high. We propose a new strategy, namely the stabilized cycle. This combines and expands upon ideas from the literature for minimizing setup and holding costs in rolling schedules, while controlling actual product-specific fill rates for a finite reporting period. A computational study with a multi-item capacitated medium-term production planning model has been executed in rolling schedules. On the one hand, it demonstrates that the stabilized-cycle strategy yields a good compromise between costs and downside deviations. Furthermore, the stabilized-cycle strategy weakly dominates the order-based strategy for both constant and seasonal demands.