ON AUTO-TUNING OF FRACTIONAL ORDER PIΛ Dμ CONTROLLERS

In this paper, a method for the auto-tuning of fractional order PIΛ Dμcontrollers using relay feedback tests is proposed. A design method for this kind of controllers is discussed, based on the magnitude and phase measurement of the plant to be controlled from relay feedback tests at a frequency of interest. Simple relationships among the parameters of the fractional controller are established and specifications such as the static error constant (kss), phase margin (ϕm) and gain crossover frequency (ωC) can be fulfilled, with a robustness argument by inspecting the flatness of phase Bode plot of the controller. An illustrative example of application is presented to show the reliability and effectiveness of the method.