AUTO-TUNING OF FRACTIONAL LEAD-LAG COMPENSATORS

Abstract In this paper, a method for auto-tuning of a fractional order lead-lag compensator using relay feedback tests is proposed. A design method for this kind of compensators 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 this 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 compensator. The auto-tuning method proposed can be taken as a first step for a latter generalization of these lead-lag compensators to the fractional PIΛDμ controllers.

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