基于简单检测方法的动态npx控制图的经济统计优化设计

Economic-statistical Optimization Design of Dynamic npx Control Chart Based on Simply Inspection

npx图是一种应用于监控连续型变量的均值变化的计数型控制图方法,具有检测简便、成本较低的优势,但对过程异常偏移的监测效率不高。为此,本文提出了一种结合动态控制图设计方法的动态npx图,并给出了平均产品长度和单位产品平均质量成本的计算方法,由此建立了动态npx图经济统计多目标优化设计模型。通过一个具体的算例与静态npx图、可变参数控制图、指数加权移动平均图等进行比较分析,结果表明本文提出的优化设计方法均优于其他几种控制图方法。

Quality has been used as a decisive factor in choosing products and services.As a result,control chart has been widely researched and applied as an effective quality control tool.When the measurement of a specific quality characteristic is expensive and time consuming,common control chart methods are often difficult to play a effective role in process control.For this reason,npx chart is proposed as an attribute control chart applied to monitor mean shifts of a variable,which has the advantages of simple measurement and cost saving,but its ability to monitoring abnormal shifts is often not strong.In order to improve the monitoring efficiency,a dynamic npx chart design method is proposed in this paper based on dynamic control chart method.As an accurate assessment of monitoring efficiency,average product length of dynamic npx chart is calculated by probabilistic method.Based on Taguchi quadratic quality loss function,average quality cost per unit of product is proposed and calculated to evaluate quality cost of dynamic npx chart.Taking average product length in control as constraint,average product length out of control and average quality cost per unit of product as objec⁃tive functions,a multi-objective optimization design model of this chart is established.A numerical example of the model is calculated by non-dominated sorting genetic algorithm(NSGA)and is used to compare with static npx chart,variable parameters(VP)chart,exponentially weighted moving average(EWMA)chart,the results show that the optimal design method proposed in this paper is superior to other control chart methods.The research will further enrich the theory of control chart optimization design,and provide an easy-to-use and efficient quality control method for quality management practice.