预防维修和VSS EWMA方差控制图联合经济决策模型

针对潜在故障导致过程质量方差漂移的可修系统,提出了一种将预防维修和监控过程方差的可变样本容量EWMA控制图联合考虑的经济决策模型.在分析确定预防维修和过程质量监控耦合机制形成的五种更新策略基础上,构建了以单位时间期望成本最小化为目标的集成决策模型.针对每种状况的期望更新成本和周期计算问题,与传统模型大多基于受控和失控两个总过程来构建的思路不同,本文采取了基于每个抽样间隔期的思路进行建模,避免了控制图平均失控运行长度计算的复杂性等问题.实例分析结果表明,本文模型由于充分考虑了预防维修和控制图两者之间耦合关系,能够获得比原先独立决策更优经济效益的决策结果.最后,利用试验设计和回归分析方法,对模型的时间和成本参数进行了灵敏度分析.

Joint economic decision-making model of preventive maintenance and VSS EWMA variance control chart

This paper develops a joint economic design approach to preventive maintenance and variable sampling size exponentially weighted moving average (VSS EWMA) chart for monitoring process variance. Incipient fault resulting in shift of process quality variance is considered and it contributes to five renewal scenarios of the production process. On this basis, a mathematical model is given to minimize the expected cost per unit time. In the model, the cycle cost and the cycle time of each scenario are established based on each sampling interval, instead of on in-control process and out-control process adopted by previous models. It can avoid the complex calculation of the average runs length during out-of-control period and other issues. The results of a case show that the hourly cost of the model is lower than that of the previous method used in the enterprise where preventive maintenance period schedule and control chart design are planed independently. Finally, orthogonal-array experimental design and multiple regressions are employed to demonstrate the sensitivity of the time and cost parameters.