Impulsive disturbance rejection in hard disk drives

This paper proposes filtering methods to cancel the impulsive disturbance contained in position error signal (PES) in hard disk drives (HDDs). The impulsive disturbances may be observed as a few single sudden changes or some consecutive changes in PES. The filtering includes impulsive disturbance identification and estimation. A recursive method is used to determine the dynamic boundaries for identification. Two methods are proposed for estimation: a linear interpolation and an adaptive least mean square (LMS) algorithm. The former is used to estimate the normal PES directly and the later is used to estimate the impulsive disturbance for cancellation. It turns out that these methods are able to effectively cancel the impulsive disturbance and do not affect the servo performance.