Disturbance attenuation fictitious reference iterative tuning using frequency domain approach

The paper gives a design method for a Fictitious Reference Iterative Tuning (FRIT) method for disturbance attenuation which can be designed using the frequency domain approach. The proposed method obtains the control parameters that optimize a performance index represented in the frequency domain, which evaluates how the closed loop frequency response is close to the ideal one in the presence of a given deterministic disturbance. The frequency domain performance index for the FRIT method consists of the Fourier transformation of one-shot experimental input-output data and disturbance signal. The paper shows that a band-path filter plays an important role in the Fourier transformation of the one-shot input-output data, and the optimal pre-filter, which well approximates the performance index to the original performance index, can be easily calculated in the frequency domain. Finally, numerical examples show that the control parameter tuning using frequency domain FRIT method with the optimal pre-filter contributes to deriving a better control parameters which improve the disturbance response.