An analytical method for the auto-calibration of PID controllers

A method for the auto-calibration of proportional integral (PI) and proportional integral derivative (PID) controllers is presented, using a frequency domain model of the plant to be controlled (obtained by relay excitation). The tuning rules of this indirect design method are derived from the symmetrical optimum principles introduced by Kessler (1958). They take in account both robustness aspects (phase margin, gain margin, sensitivity, neglected dynamics) and desired closed loop characteristics. They also cover a large domain of current real applications. The proposed method is compared with the Ziegler-Nichols method both theoretically and experimentally. Results from industrial experiences are given.<>