An interpolated DFT based adaptive notch filter for missile bending mode suppression

An interpolated Discrete Fourier Transformation (IpDFT) based adaptive notch filtering method is proposed to solve the problem that the conventional notch filter can cause a serious phase lag because flexible missile has uncertain low and wide range bending modes. A modified Jacobsen estimator is used to identify and track a bending frequency, and then the center frequency of the notch filter is tuned according to the bending frequency. The estimator closely follows the Cramer-Rao lower bound (CRLB), even when the amplitude of the bending mode is time-varying. The performance of the proposed method is verified by computer simulation, and high sensitivity, short identification time and fine resonant suppression of the method are demonstrated. Indeed, compared to the non-adaptive notch filter, the phase lag is reduced from 29.4° to 11.86°. Compared to another kind of adaptive notch filter (ANF) based filtering method, the identification time is reduced from 2 s to 0.25 s, and the bending mode amplitude is 10% of that.