The stability analysis and optimal design of discount factors for Double EWMA controller

• Main Authors: Yi-Xian Zhou, 周宜賢
• Other Authors: Ming-Shan Lu
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/44343459013547252938

碩士 === 雲林科技大學 === 工業工程與管理研究所碩士班 === 99 === The run-to-run controller which integrates the SPC and EPC is widely applied to MIMO manufacturing systems nowadays. Double EWMA controller is a kind of run-to-run controller. Mainly, it adjusts the intercept and disturbance items of the estimated process and then generates the controllable input recursively so the stable process outputs are close to the targets. Double EWMA controller is used to avoid the unstable phenomenon of process output which is caused by the shift, drift and white noise generated by machine wear and different material quality et al. The performance of the Double EWMA controller is determined by the choice of discount factors. In this research, the stable analysis and optimal design of discount factors for the Double EWMA controller are proposed. First, the recursive least square (RLS) method is used to construct the process model. Based on the process model, the state space method is applied to analyze the stability of the system and to determine the scope of discount factors under the stable condition. Then, the optimal discount factors are searched by the ant algorithm method under the stability condition. The objective is to minimize the cost of the output deviating from the target and the adjustment amounts of the control input between each run. A chemical mechanical polishing (CMP) process is given as an example to verify the proposed concept.