Tuning of fractional PID controllers by using QFT

As it is known, a wide range of research activities deal with the application of the Quantitative Feedback Theory (QFT) for the design of different control structures. All these approaches generally use rational controllers. On the other hand, the importance of fractional order controllers is becoming remarkable nowadays, studying aspects such as the analysis, design and synthesis of this kind of controllers. The purpose of this paper is to apply QFT for the tuning of a fractional PID controller ((PID mu)-D-lambda) of the form K-P (1 + K(I)s(-lambda) + KDS mu), where lambda, mu are the orders of the fractional integral and derivative, respectively. The objective is to take advantage of the introduction of the fractional orders in the controller and fulfill different design specifications for a set of plants.