A Direct PID Gain Tuning Based on FRIT Method Using Optimal Filter in the Frequency Domain

The paper gives a PID gain tuning method using a Fictitious Reference Iterative Tuning (FRIT) approaches in the frequency domain. The proposed method obtains the PID gains that optimize a performance index, which evaluates the difference between the closed loop output and the reference model output in the frequency domain. The performance index is calculated using the Fourier transformation of one-shot experimental input-output data. The paper shows that a bandpath 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, and contributes to deriving a better PID gains improving the closed loop response through numerical examples.