Patent ID: 7876523

Claim:
A disk drive comprising: a disk comprising a plurality of spiral tracks, wherein each spiral track comprises a high frequency signal interrupted by a sync mark at a sync mark interval; a head actuated over the disk; and control circuitry operable to: position the head over the disk; use the head to read the spiral tracks to detect a plurality of spiral-to-spiral times each representing a time between consecutive spiral crossings; estimate a velocity of the head in response to the spiral-to-spiral times; generate velocity feedforward compensation values from the estimated head velocity; generate a control signal to position the head over the disk in response to the velocity feedforward compensation values; when the detected spiral-to-spiral times are substantially constant, initialize position feedforward compensation values in response to the velocity feedforward compensation values; estimate a position of the head in response to the spiral tracks; and servo the head in response to the estimated head position and the position feedforward compensation values.