Direct synthesis-based fractional-order PID controller design: application to AVR system

In this paper, a novel method for tuning PIλDμ controllers is proposed. Based on the direct synthesis approach, the proposed technique consists of taking the closed-loop system equivalent to Bode's ideal loop transfer function. Using a semi-analytical technique, the parameters of the controller are derived from the desired closed-loop transfer function and the plant's input/output signals without using any identification technique. Simulation examples are given to show the efficiency and the applicability of the proposed method to high-order and time delay systems. The results confirm that the proposed controller satisfies the dynamics requirements with iso-damping property when compared with two other related tuning methods. As an application example, the proposed tuning method is applied to the automatic voltage regulator system in order to study the efficiency and robustness of the proposed controller.