A disturbance observer approach to detecting and rejecting narrow-band disturbances in hard disk drives

This paper presents a servo compensator to detect and reject narrow-band disturbances in the non-repeatable runout (NRRO) for hard disk drives (HDDs). A disturbance observer (DOB) with a band-pass Q filter is used to detect the presence of the narrow-band disturbance. Once the disturbance is detected, the frequency of the disturbance is identified by the least mean squares (LMS) algorithm. Based on the frequency estimate, a narrow band-pass Q filter centered at the estimated frequency is applied to the DOB to compensate for the disturbance. The performance of this compensator is demonstrated by simulation on an open-source realistic hard disk drive model.