Abstract: A disc drive 22 having a head 26 actuated by an actuator 32 for seeking out a destination track 30 includes servo velocity control circuitry 51 and servo position control circuitry 41. The servo velocity control circuitry 51 seeks out the destination track and places the head within the boundaries of that track while the servo position control circuitry 41 using servo information places the head on the centerline of the destination track. The fine servo control circuitry 20 is provided for communicating the information generated by the servo position control circuitry 41 to the servo velocity circuitry 51 when the head 26 is several tracks from the destination track in order to allow the actuator 32 to smoothly and quickly cause the head to seek within the boundaries of the destination track without overshooting that track.

Abstract: A disc drive 22 having a head 28 actuated by an actuator 27 includes a head loading velocity control for successfully and accurately loading the head 28 onto a disc 26 so as not to cause damage to the head 28 or the disc 26.

Abstract: Disclosed is a servo control apparatus for controlling a servo means that positions a recording head over a disk-shaped data storage medium. If the disk-shaped data storage medium is improperly mounted on a disk drive causing wobble of the disk as it turns, then the problem of runout occurs so that each of the tracks of data on the disk do not pass directly under the head throughout the whole rotation of the disk. The present invention provides a reference track near the outside circumference of the disk on which reference data is stored in a plurality of bursts spaced around the reference track. The servo control apparatus detects the reference data for each of the bursts and calculates the position of the centerline of the reference track with respect to the head for each of the bursts.