Patent ID: 6826006
Filing Date: 2004-11-30
Classification: G11B

Abstract:
In a magnetic disk drive having a head disk assembly (HDA) and a sampled servo controller, the HDA including a rotating magnetic disk having distributed position information in a plurality of uniformly spaced-apart servo wedges, and an actuator for positioning a transducer head in response to a control effort signal, the transducer head for periodically reading the position information from the servo wedges, the sampled servo controller for periodically adjusting the control effort signal during a track-following operation based on the position information, a method for recursively determining repeatable runout cancellation values comprising the steps of:a) storing initial resonant filter states, each initial filter state corresponding to a servo wedge of a predetermined track; b) filtering the stored resonant filter states to substantially compensate for effects of the sampled servo controller, which effects tend to distort position error signals generated during track following, to generate current repeatable runout cancellation values, wherein a current repeatable runout cancellation value is generated for each servo wedge; c) reading the position information related to the predetermined track during track following for a disk rotation to generate position error signals based on the read position information and the current repeatable runout cancellation values; d) scaling the position error signals to generate convergence values, wherein a convergence value is generated for each servo wedge; e) applying each convergence value to each corresponding stored resonant filter state to generate a resulting updated resonant filter state; f) storing the updated resonant filter states to replace the previously stored resonant filter states; and g) repeating steps b), c), d), e) and f) until a predetermined threshold is obtained thus recursively determining the repeatable runout correction values.