A simple procedure to design PID controllers in the frequency domain

In this paper, a simple method to design PID controllers in the frequency domain is proposed. The method is based on the use of a single tuning factor, defined as the quotient between the final cross over frequency and the zero of the controller. Classical methods described in the basic control books propose to fix the above parameter in a predetermined value (usually 10), independently of the process model. Several examples show that this fixed value is not the best choice in general, in the sense that the behavior can be greatly improved if an adequate tuning of that parameter is done. A tuning procedure for the parameter is also proposed, based on the maximization of a controller gain. The procedure is valid for PI, PD and PID controller design, and is tested with a set of well known benchmark systems for PI and PID design and compared with other (more complex) approaches.