ABSTRACT

Quality control charts are extensively used to monitor processes. The EWMA chart is a good alternative to the Shewhart chart to quickly detect small and moderate shifts in the process mean. The DEWMA charting procedure is an enhanced approach for the EWMA chart and performs much better, especially for small and moderate shifts. In this article, we propose the triple EWMA (TEWMA) chart in an effort to improve much more the detection ability of the classical EWMA chart. Monte Carlo simulations are used to evaluate the run-length characteristics of the proposed chart. A comparison study versus the DEWMA, EWMA and GWMA charts indicates that the TEWMA chart with time-varying control limits is more effective in detecting small shifts while it is comparable with the other charts in moderate and large shifts. Moreover, the proposed chart has better inertia properties than the competing charts and is also shown to be in-control robust for small values of the smoothing parameter. Finally, two examples are given to display the application of the TEWMA chart.

摘要

质量控制图广泛用于监视过程。EWMA图表可以很好地替代Shewhart图表，以快速检测过程平均值中的中小变化。DEWMA图表过程是EWMA图表的增强方法，并且执行效果要好得多，尤其是对于中小班次。在本文中，我们提出了三重EWMA（TEWMA）图表，以期进一步提高经典EWMA图表的检测能力。蒙特卡洛模拟用于评估建议图表的游程长度特征。与DEWMA，EWMA和GWMA图表进行的比较研究表明，带有时变控制极限的TEWMA图表在检测小变速时更有效，而在中等和大变速时它可以与其他图表相提并论。而且，建议的图表具有比竞争图表更好的惯性属性，并且对于较小的平滑参数，也显示出控制上的鲁棒性。最后，给出两个示例来显示TEWMA图表的应用。