A Cumulative Score Control Scheme for detecting process shift: Operating Characteristic and Design Strategy

• Main Authors: I-Che Huang, 黃一哲
• Other Authors: Cheun-Sheng Cheng
• Format: Others
• Language: zh-TW
• Online Access: http://ndltd.ncl.edu.tw/handle/58606828036441813065

碩士 === 元智大學 === 工業工程研究所 === 82 === Control charting is an important technique in statistical process control.It is often used to determine if a manufacturing process has achieved a state of control and to detect the out-of-control situations. A process is in control if no point falls outside the control limits or no systematic variations are present in the process data. Over the years, Shewhart control charts have been the most widely used control scheme in industry. They are simple to use and can detect large shifts faster than other cont ol schemes. A criticism of Shewhart control schemes is that they only use the information about the process contained in the last observation. This feature makes Shewhart control charts relatively insensitive to small shifts in the process mean. In this research, a cumulative score control procedure based on a single control statistic has been developed. The proposed control procedure is designed to supplement the traditional Shewhart charts in detecting small process shifts. The ARL properties of the proposed schemes were determined by a finite state Markov chain. An extensive comparison shows that the ARL properties of the improved cumulative score procedure are comparable to those of Shewhart-CUSUM control schemes. The proposed scheme required only simple algorithmetic and is very easy to implement.