Patent ID: 6972922
Filing Date: 2005-12-06
Classification: G11B

Abstract:
1. A magnetic disk drive, comprising: a head disk assembly (HDA) including a rotating magnetic disk having distributed position information in a plurality of uniformly spaced-apart servo wedges for defining data storage tracks, and including 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 and reading data from the data storage tracks; and a sampled servo controller for periodically adjusting the control effort signal during a track-following operation based on the position information and repeatable runout (RRO) cancellation values; wherein the magnetic disk stores RRO information relating to predetermined RRO cancellation values, for at least one data storage track, for reducing effects of RRO in the distributed position information during track following of the respective data track, the RRO information for the at least one data storage track including at least one first data structure having a first predetermined number of data bits for representing an initial RRO cancellation value, and including at least one second data structure having a second predetermined number of data bits associated with a respective subsequent RRO cancellation value, the first predetermined number of data bits being greater than the second predetermined number of data bits.