一种多指标质量动态控制图及其应用

Multivariate Dynamic Quality Control Chart and Its Application

研究了将多指标在一个图上标示的多指标控制图。提出了三种质量控制限并作了比较。控制上限(UCL)取Hotelling的T2统计量的α/2上侧分位数。预控上限(UPCL)取Hotelling的T2统计量的λα/2上侧分位数。当第k个观测点的T2k值超过UPCL时,则接下去的抽样区间将缩短,以便及早发现失控状态。对超出控制限的情况下如何确定哪一个质量指标发生异常的问题,提出了一种可靠的分析方法。用这种方法解决了某卷烟厂的烟丝生产过程中的多指标质量控制和管理问题。

Several correlated process eharaeteristies are usually measured simultaneously in manufacturing for monitor the quality . Multivariate control charts which eombine multiple eharaeteristies into a single chart are used to monitor industrial process. Three kinds of control limits are given and compared with each other. The upper control limit （UCL） is obtained by determining the α/2 quantile of the T^2 distribution to give a false alarm rate of α/2. The upper predietion eontrol limit （UPCL） is obtained by determining the 1 -λα/2 quantile of the T^2 distribution. When a value of T^2 exeeeds an UPCL , the next sampling interval is reduced. Once an out-of-control signal is given ,it is diffieuh to determine which component of process is out of control . We propose a diagnostic method to distinguish the component which is out of control. An application of this procedure can be illustrated using a cigarette silk quality monitoring example that 76 observations were measured on five variables.