Adaptive Control Scheme for a Process with Incorrect Adjustment

This article considers an adaptive process control scheme for a process with incorrect adjustment. Incorrect adjustment of a process may result in shifts in both the process mean and variance, ultimately affecting the quality of products. We construct control charts with adaptive sampling intervals (ASI) to control the quality variable produced by the process with incorrect adjustment. The performance of the proposed control charts is measured by the adjusted average time to signal derived by a Markov chain approach. An example of process control for automobile braking system shows the application and the performance of the proposed control charts in detecting small and medium shifts in mean and variance. Furthermore, some numerical analysis results show that the performance of the ASI control charts is much better than the FSI control charts in detecting small and medium shifts in mean and variance.