Adaptive disturbance rejection in the presence of uncertain resonance mode in hard disk drives

An adaptive on-line scheme is designed to identify the uncertain and time-varying resonance modes in hard disk drive servo systems. Based on the identified results, the uncertain resonance mode is extracted and a peak filter is designed accordingly to provide stronger capability of disturbance suppression. The scheme does not require any extra excitation signal nor additional signal processing for the parameter identification. Compared to conventional method, the rates of learning and error convergence are greatly increased. The scheme can provide good stability margin at high frequency subject to the variation of the resonance frequency and the peak gain. Simulation results show the validity and effectiveness of the proposed scheme.