New control charts for monitoring frequency and magnitude of critical events

• Main Author: Qu, Liang.
• Other Authors: School of Mechanical and Aerospace Engineering
• Format: Theses and Dissertations
• Language: English
• Published: 2013
• Subjects: DRNTU::Engineering::Industrial engineering
• Online Access: http://hdl.handle.net/10356/51341
• Institution: Nanyang Technological University

Quality is an extremely important feature for satisfying customers and winning market shares nowadays. When a quality problem occurs, it is crucial to detect it quickly in order to avoid serious consequence and economic loss. A very effective method in Statistical Process Control (SPC) is control chart which is used for monitoring important quality characteristics in the processes. A major category of SPC chart is the control chart for monitoring Time between Event (TBE). The TBE control charts are particularly effective for high yield production line with very low defect rate. Its applications can be extended to many non-manufacturing sectors. The studies for this category of charts are relatively fewer compared with the studies for other types of charts. Especially, most of the studies for event monitoring focus on the time interval between events only, but completely neglect the magnitude of the events. This thesis proposes several new TBE control charts to achieve the highest overall detection effectiveness. All of the four projects in this thesis focus on the development of the advanced charts for monitoring TBE and/or the magnitude of an event. An optimal model which uses an overall performance measure, Average Loss (AL), as the objective function is adopted to design these charts. The performance of these charts is compared with that of the most effective TBE charts in the literature. The results convincingly show that the proposed new control charts outperform all existing charts in overall detection effectiveness to a significant degree.