风险质检行为下的模糊生产-库存决策

Fuzz Decision of Production-inventory with Quality Screening Risk

本文研究在风险质检行为下需求与生产率具有模糊属性的由一个制造商与一个零售商构成的生产-库存问题。在假设制造商生产的产品存在质量缺陷,零售商在质检过程中存在质检风险的基础上,分别建立了需求模糊下的生产-库存总成本模型,需求与生产率模糊下的总成本模型,运用符号距离法进行了逆模糊化处理,将模糊化的生产-库存总成本转化为确定性成本。证明了两类情形下的总成本均是关于最优订购量与最优缺货量的联合凸函数。数值分析结果表明：随着期望缺陷率的增加,最优订购量增加,最优缺货量减少,最优成本增加,且最优成本增加的速度越来越快。一类质检风险增大引起总成本增加,二类质检风险增大引起总成本减少。最优订购策略对质检一类风险敏感,对质检二类风险不敏感。

During production, product quality is not always perfect, since it is directly affected by the reliability of the production process. To ensure the customer requirement of quality, quality screening is neces- sary. However, the inspector may make inspection errors during the screening process, which leads to two types of quality inspection risk, i. e. , type- I risk and type- II risk. Due to quality inspection risk,shortages may sometimes occur. On the other hand, there is uncertainty outside demand, and it is fuzzy. In the meanwhile, the productivity is also changeable, which is also fuzzy. Based on these internal and ex- ternal fuzzy demand and fuzzy productivity, as well as the quality inspection risks, a two-level production -inventory decision with fuzzy demand and fuzzy production rate is studied. In the production-inventory system, there is one manufacturer and one retailer. The manufacturer produces imperfect quality products and delivers the products to the retailer in small lots of equally sized shipments. Upon receipt of the prod- ucts, the retailer will conduct a 100% inspection. As mentioned before, quality screening risk may occur for the retailer. By using JIT philosophy, the retailer has to determine the optimal order size and backorde- ring quantity, and the manufacturer has to determine the optimal production batch and the optimal number of shipments between the manufacturer and the retailer per production cycle. The objective of this study is to minimize the total joint annual costs incurred by the manufacturer and the retailer. The signed distance method for fuzzy numbers is employed to transform the fuzzy total cost into the crisp cost. The total cost is proved to be a joint convex function of the size of the shipments and the backordering quantity of the retailer. Numerical examples show that with the increase of the expected defect rate, the optimal ordering quantity increases, the optimal backordering quantity decreases, and the optimal cost increases with a fast rapid speed. Type- I risk makes total cost increase, but type- II risk makes total cost decrease. The optimal ordering strategy is sensitive to type- I risk, but not sensitive to type- II risk. The contributions of this study are twofold. First, the inspection risk behavior is incorporated into the optimal decisions of the JIT production-inventory model. Second, the fuzzy demand and fuzzy production rate are considered to establish the model.