A new adaptive Smith predictor controller

The principle of normal-mode-inaction (NMI) adaptation is utilized to derive an adaptive Smith predictor controller. This new adaptive system differs from a conventional adaptive Smith predictor in that the adaptation of its control parameters only occurs during the instances of an unambiguous abnormality. This abnormality is defined as a significant change in the magnitude or phase of certain points on the continuously tracked Nyquist plot. The ability of the NMI adaptive Smith predictor controller to overcome the effects of an unmeasurable load disturbance is superior to that of the conventional adaptive Smith predictor. The NMI adaptive Smith predictor controller uses a relay auto-tuner, and the adjustment of the controller parameters is based on the Ziegler-Nichols tuning formula. Simulation examples demonstrate the usefulness and the advantages of the new adaptive control scheme