Robust tuning of PID controllers via uncertainty model identification

A tuning method for a controller of given structure is proposed. with particular emphasis on the PID form. The method consists in the processing of experimental results and "a priori" information on the plant to be controlled. in order to obtain a plant uncertainty model, composed of a nominal model and a bounded perturbation representing the modeling error. The number of poles and zeros of the controller being fixed, a procedure is described. which allows to obtain the so called robust Q set. This is the set of the controller parameter values for which the desired performance specifications are satisfied, whatever plant perturbation may be present within the previously estimated uncertainty model. Evaluating the robust Q set and pointing out performances that constraint its boundary constitute a good aid for the designer to tune controller parameters, in order to achieve a suitable balance among the closed loop performances that can be guaranteed on the actual plant.