Direct Adaptive Disturbance Observer Design for Rejecting the Narrow-Band Disturbance With Unknown Frequency in Hard Disk Drives

This paper presents an adaptive add-on compensator to handle a single narrow-band disturbance with unknown frequency in hard disk drives (HDDs). A disturbance observer (DOB) loop with a narrow band pass Q filter is built around the baseline servo controller to reject the narrow-band disturbance. The frequency parameter of the Q filter is directly adapted to the optimal value in the sense of minimizing the track following track mis-registration (TMR). The performance of the proposed compensator is demonstrated by simulation on an open-source realistic hard disk drive system.