Western Digital Technologies, Inc.

John Yin Kwong Li

Jonathan V Nguyen

Guoxiao Guo

Jie Yu

Duc T Phan

Robert J McNab

Kuang-Yang Tu

Hemant Melkote

David D Nguyen

Aswartha Narayana

David Dung Tien Nguyen

Teddy T C Chen

Eugene Chun-Tsing Wu

Gary Gaoxiang Zhu

Tuong M Vu

A disk drive for implementing a head switch operation is disclosed. The disk drive comprises: an actuator; a first head and a second head attached to the actuator; a disk having a plurality of tracks; and a processor. The processor controls operations in the disk drive including: executing a head switch command from the first head to the second head; determining that a sync-up operation is not successful for the second head at a first track; applying a torque to the actuator to move the second head to a second track; and determining that the sync-up operation is successful.

Head switch operation for a disk drive

The present invention may be embodied in a magnetic disk, of a disk drive, having eight-bit fields storing wedge repeatable runout (WRRO) compensation values and redundancy information. The WRRO compensation value of each field includes a six-bit binary value of which five bits represent a compensation magnitude and one bit represents a sign bit indicating a compensation direction. The redundancy information of each field has a first bit based on the sign bit.

Magnetic disk having efficiently stored WRRO compensation value redundancy information and method for using the redundancy information

A disk drive is disclosed comprising a plurality of servo sectors that define a plurality of tracks, and a head comprising a read element radially offset from a write element. The read element is positioned over a first track, and the first track is read to generate first read wedge repeatable runout (WRRO) values. A first seek operation of the head positions the read element over a second track, and the second track is read to generate first write WRRO values. The first write WRRO values are used to write the first read WRRO values to the first track. A second seek operation of the head positions the read element over a third track, and the third track is read to generate second write WRRO values. The second write WRRO values are used to write the first write WRRO values to the second track.

Disk drive writing wedge RRO values in a butterfly pattern

A method is disclosed for identifying wedge time shift zones on a magnetic disk of a disk drive. The disk drive further includes a spindle motor for rotating the disk at an operating speed in response to a spindle control current generated by a spindle control system, and a head that is actuated over the disk. During operation, the control systems causes a seek of the head across the disk and measures wedge-to-wedge times between servo wedges. The control system then calculates a wedge-to-wedge time shift value using the wedge-to-wedge times and determines whether the wedge-to-wedge time shift time value exceeds a predetermined threshold. If the wedge-to-wedge time shift value exceeds the predetermined threshold, then the control system identifies a wedge time shift zone, and stores information for compensating for the identified wedge time shift zone during disk operations.

Method for wedge time shift calibration in a disk drive

A method for reducing an estimation period for repeatable runout (RRO) errors in a disk drive comprising a head, a disk surface having a track partitioned by servo-wedges, and a servo control system for controlling the movement of the head relative to a track during revolutions of the disk. The method includes estimating the RRO errors of the track based on a) a series of position error signal values obtained during a current revolution of the disk surface, and b) a previous estimation of the RRO errors of the track obtained during a previous revolution of the disk surface and determining a differential value between a first measure of the estimated RRO errors and a second measure of the previous estimation of RRO errors, and repeating the estimating and determining for subsequent revolutions of the disk surface until the determined differential value is smaller than a pre-selected threshold value.

Reducing estimation period for repeatable runout errors in a disk drive

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Laguna Niguel, CA, United States of America

John Yin Kwong Li