在傳統上,管制圖之設計都只是考慮到統計層面,其注重於樣本大小的 選擇及管制界限,用來偵測製程是否落於管制界限中,然而都忽略了管 制圖的經濟層面,例如﹕消除可歸屬原因的成本、抽樣及檢驗成本、調 查管制外相關訊息成本、製程在管制中或管制外的利潤、產生不良品所 造成的成本損失 (不合格品遭顧客退回的損失) 等。根據經濟層面來設 計管制圖之步驟稱為管制圖之經濟設計。管制圖經濟模式之設計是指要 決定下列三個參數:(1) 抽樣樣本大小,(2)抽樣間隔,(3) 管制界限。 過去有關管制圖經濟模式之最佳參數設計之研究,由於牽涉太多數學公 式而須以近似方法求解。本研究主要的目的是要以基因演算法的求解觀 念,運用於管制圖經濟模式之最佳參數的求解,我們以田口方法找出基 因演算法中較佳參數水準的組合。本研究以 -R管制圖之設計及 管制圖 加入警告界限兩種模式來驗證。研究結果顯示基因演算法之求解品質與 傳統方法相似或可優於傳統方法。
Traditionally, control charts have been designed with respect to statistical criteria only. This usually involves selecting the sample size and control limits such that the power of the test to detect a particular shift in the quality characteristic and the type I error probability are equal to specified values. The design of a control chart has economic consequences in that the costs of sampling and testing, costs associated with investigating out-of-control signals and possibly correcting assignable causes, and costs of allowing nonconforming units to reach the consumer are all affected by the choice of the control chart parameters. This research applies the genetic algorithm to determining the parameters in the economic design of control charts. Taguchi*s design experiment is employed to determine some important parameters of genetic algorithm. The performances of the genetic algorithm are verified using the economic design of x-bar-R control charts and x-bar control charts with warming limits. The results show that the genetic algorithm performs as well as or better than traditional methods.