Automatic tuning of the modified Smith predictor controllers

A simple relay feedback automatic tuning method is proposed for the modified Smith predictor, to provide a controller for stable, unstable and integrating processes with long dead time. A single asymmetrical relay feedback test is used to obtain a reduced order process model in terms of a second order dynamics plus dead time model. Very simple but straightforward tuning formulae are derived for the controllers which have a simple relationship with the plant model parameters. Thus the plant model blocks in the Smith predictor structure, as well as all the controllers are designed from a single asymmetrical relay test. Excellent performance of the auto-tuned Smith predictor has been substantiated by simulations