变样本容量比例控制图设计及应用

针对单边休哈特比例控制图失控状态下平均报警时间长的问题,提出一种单边变样本容量比例控制图来监控两个正态变量间比例的偏移。采用马尔可夫链方法计算了该控制图的平均运行链长。在保证过程处于受控状态的统计性能基础上,使失控状态下的平均运行链长最小,从而获得控制图的最优决策变量和最优性能指标。仿真结果表明,单边变样本容量比例控制图的性能明显优于单边休哈特比例控制图。最后将该方法应用于港口皮带机配煤比例监控的问题,通过仿真实验说明了该方法能够对煤炭配比过程中的比例偏移做出有效反应。

Design and Application of Ratio Control Charts with Variable Sample Size

Aiming at the problem of long average alarm time for out of control(OOC)situation of the one-sided Shewhart-RZ ratio control chart,we proposed a one-sided variable sample size ratio control chart to monitor the deviation of the ratio between two normal variables.Then,using Markov chain method,we calculated the average performance chain length of said control chart.On the basis of the statistical performance capable of keeping the process under the controlled state,we minimized the average performance chain length for the OOC state,so as to obtain the optimal decision variable and performance index of the control chart.The simulation result shows that the performance of the one-sided variable sample size ratio control chart is obviously better than that of the one-sided Shewhart-RZ ratio control chart.Finally,we applied this method to the monitoring of port belt conveyor coal blending,and found that this method can respond effectively to the ratio deviation in the process of coal blending.