On Fractional PID Controllers: A Frequency Domain Approach

Abstract A more general structure for the classical PID controller is proposed in this paper by using fractional integral and differential operators. A frequency domain approach is used to show the advantages of using these fractional PID controllers, which can be sumarized in the possibility of dealing with a more general class of control problems, in which the fractional nature of the controller can be imposed by the fractional nature of the system to be controlled, or by the special nature of the required time or frequency responses. Some illustrative examples and comments on controller tuning and realizations are given.