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Messina, Montgomery, Keats & Runger

EWMA and tracking signal on the manipulated variable is to quickiy indicate that an assignable cause has occurred. The generał role of the appropriate statistical monitoring scheme on the deviation from target is two-fold : (1) To ensure that when an assignable cause has occurred it will eventually be found, and (2) to reduce the number of false alarms when the process is in a State of statistical control.

Summary

The results of this study have demonstrated that veiy effective integrated EPC/SPC strategies can be developed for the control engineer to employ in practice. The three strategies proposed for usage employ monitoring both the deviation from target and the control action. The cost objective of the process under examination dictates which strategy should be employed in practice.

References

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Box, G. E. P. and Jenkins, G. M. (1976), Time Series Analysis : Forecasting and Control, 2nd Ed. San Francisco : Holden-Day.

Box, G. E. P. and Kramer, T. (1992), "Statistical Process Monitoring and Feedback Adjustment-A Discussion," Technometrics, 29, 393-400.

Deming, W. E. (1993), The New Economics For Industry, Government, Education, Cambridge, MA, MIT Center for Advanced Engineering.

English, J. E. and Case, K. E., (1990) "Control Charts Applied as Filtering Devices Within a Feedback Control Loop." 11E Transactions, 22 (3), 255-269.

Harris, T. J. and Ross, W. H. (1991), "Statistical Process Control Procedures for Correlated Observations," The Canadian Journal of Chemical Engineering, 69, 48-56.