Finite-Frequency Identification: Selftuning of Test Signal

A linear stable plant with unknown coefficients in the presence of an unknown-but-bounded disturbance is considered.The finite-frequency technique for identification of the plant makes use of a test signal with minimal number of harmonics (this value is equal to a plant state-space dimension). It is shown that if frequencies of the test signal are chosen outside of a natural frequencies band (where log magnitude of plant has corner frequencies) then identification results may very strongly depend on errors of the frequency characteristics determination. In order to find a estimate of the boundaries of the natural frequencies band a procedure of selftuning of test signal frequencies is given. Test signal amplitudes are selftuned as well. It provides the prescribed boundaries of the input and output plant.