Abstract
An improved continuous-cycling method is proposed for the autotuning of the proportional−integral−derivative (PID) controller. The proposed method can identify the frequency response of the process at a preset phase angle without a modeling error. Moreover, it provides an exact frequency response even if a static disturbance is present. The proposed method is an improved version of the continuous-cycling method. The gain of the proportional controller in the continuous-cycling method is updated to obtain the continuous-cycling status automatically. To guarantee the preset phase angle of the frequency response, we place a phase shifter in the form of a time delay after the proportional controller. The results of simulation and experimental studies show that the proposed method can provide an exact frequency response even under static disturbance conditions and can be applied to real processes.