An LQ self-tuning controller with reduced nonminimum phase model

The robustness of an LQ self-tuning controller is considered. An implicit algorithm is used to identify parameters of both the plant and the controller. The frequency-weighted estimator is used to capture the nonminimum phase nominal plant in the face of plant uncertainty. Simulation results are displayed to demonstrate the robustness property of the proposed scheme. An improved stability robustness compared with model reference adaptive control is obtained. The frequency-domain weighted estimator uses a Butterworth filter with the cut-off frequency in the intermediate range together with the desired closed-loop polynomial with a relatively high-pass property to capture the reduced-order nonminimum phase model in the set