Performance of an adaptive algorithm for sinusoidal disturbance rejection in high noise

The paper proposes a discrete-time algorithm for the rejection of sinusoida l disturbances of unknown frequency. The algorithm is adapted from an exist ing continuous-time algorithm and the overall nonlinear system is analyzed using a linear approximation. The paper shows that the noise rejection prop erties may be predicted using an in-phase/quadrature decomposition of the n oise similar to the one encountered in the theory of phase-locked loops. Es timates are obtained for the standard deviations of the plant output and of the adaptive parameters. Simulations validate the predictions of the analy sis, despite the nonlinear nature of the adaptive system and the high level of noise applied. (C) 2001 Elsevier Science Ltd. All rights reserved.