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Abstract

A secondary servo compensator, in a miniature disk drive having at least one disk and a servo system to position an actuator driven read/write head over any one of a number of tracks on the disk, provides on-line real-time compensation for disk runout that occurs during operation of the miniature disk drive. The servo system includes a servo compensator that has a gain and that generates an actuator position signal for positioning the read/write head over the track in response to a position error signal. The secondary servo compensator functions independently of the servo compensator. Specifically, the secondary servo compensator receives the position error signal and analyzes the disk runout and simultaneously generates a runout compensation signal during operation of the disk drive, i.e., while the disk drive is idle, reading, or writing. An actuator signal generator combines the actuator adjustment signal that is generated using the position error signal from sector 'i' and the runout compensation signal that is generated using the position error signal for sector 'i-1' to create a runout compensated actuator signal for sector 'i'. Hence, the runout compensation is fed forward. The servo system, using the information from the servo compensator and the secondary servo compensator, continuously maintains the read/write head over the desired track centerline independent of the offset of the center of the disk from true center of rotation.

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