A new nonparametric identification procedure for online controller tuning

The automation of the Ziegler-Nichols sustained oscillation method through the use of an online relay experiment by Astrom and Hagglund has initiated a wide range of research investigations. Some of these studies have been related to rules for PID control design, but other studies have taken inspiration from the autotune culture and have sought alternative ways of performing the nonparametric identification task of the relay experiment. In this paper a new nonparametric method is described based on a digital phase-lock loop principle. The flexibility of the method to solve different frequency domain identification problems is explored. Simulation results to illustrate the accuracy obtainable are given