Abstract
A simple PI/PID controller tuning formula is presented in this article, where the maximum closed-loop amplitude ratio in the frequency domain is set to +2 dB, a value recommended by Luyben (1990) for considering performance robustness. A first-order-plus-dead-time (FOPDT) model or a second-order-plus-dead-time (SOPDT) model is first identified for process dynamics. The PI/PID settings for the FOPDT/SOPDT models are then derived based on the internal model control (IMC) principle. The robustness parameter left for adjusting in the IMC tuning is determined according to the specified value of maximum closed-loop magnitude. Several testing processes with an extensive variety of dynamic characteristics are used, demonstrating the effectiveness and robustness of the proposed tuning method on typical processes.
