An Efficient Method for Tuning of FOPI Controllers: Robustness to Order Variations of the Plant

Existence of uncertainties in the model of real-world plants can trouble the control system designer in achievement of control objectives in control of such plants. In modeling of these plants by benefiting from fractional order models, one of the most commonplace types of uncertainties is the order uncertainty. This paper deals with presenting a method for tuning fractional order PI (FOPI) controllers to be used in control of plants, modeled by fractional order transfer functions consisting of a fractional order pole in addition to a time delay, such that the control system is robust against order variations. By the proposed tuning method, values of phase margin and gain crossover frequency are adjustable in the nominal case. Furthermore, the resulting control system will be robust against order uncertainties. Numerical simulation results are presented to confirm the effectiveness of the proposed tuning method.