AUTOMATIC TUNING OF PID REGULATORS IN PRESENCE OF MODEL PERTURBATIONS NEAR THE DESIRED CLOSED-LOOP CUTOFF

A method for the automatic tuning of PID regulators is presented. The proposed technique relies on the closed-loop identification of two points of the plant Nyquist diagram, and is specifically aimed at improving robustness against model perturbations with significant effects near the desired cutoff frequency. This is achieved by means of convenient tuning formulae, which allow one to impose some control on the direction along which the open-loop Nyquist diagram will cross the unit circle. Also, attention is paid so as to achieve low computational effort and moderate tuning time.