Method and apparatus for offset control in a disk drive

Abstract

According to one embodiment, a disk drive capable of performing a dynamic offset control (DOC) is provided. The disk drive has an offset module and an updating module. The offset module calculates an offset value that changes during a one-rotation period of a disk, from the offset-measuring position data recorded in the disk. The updating module updates the offset value to a new one if a disk shift has occurred.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2008-304835, filed Nov. 28, 2008, the entire contents of which are incorporated herein by reference.BACKGROUND[0002]1. Field[0003]One embodiment of the present invention relates to a disk drive such as a hard disk drive. More particularly, the invention relates to a technique of controlling the offset between the read head and the write head, both incorporated in a disk drive.[0004]2. Description of the Related Art[0005]Most disk drives, a representative example of which is the hard disk drive, have a magnetic head that may record data in, and reproduce data from, a disk, i.e., magnetic recording medium. The magnetic head is mounted on a rotary-type actuator. The magnetic head can be moved in the radial direction of the disk and can be positioned at a target track (or cylinder) provided on the disk.[0006]The magnetic head has a read head...

AI Technical Summary

Benefits of technology

The patent text describes a technique for controlling the offset between the read and write heads in a disk drive. The technique takes into account the offset between the read and write heads when the magnetic head is positioned at a different position on the disk. The problem addressed by the patent is the need for accurate offset control to ensure accurate positioning of the magnetic head, even in the event of a disk runout or impact. The patent proposes a method for measuring the offset value directly, which is important for accurate positioning of the magnetic head.

Problems solved by technology

This results in a servo-track runout.

Consequently, accurate offset control can no longer be performed on the magnetic head in the same track, because the offset value remains unchanged while the disk is rotating 360°.

Further, another disk runout develops when the disk with the servo data recorded on it is incorporated into the disk drive.

However, the offset value calculated by this method is far from accurate.

This method can hardly provide an accurate setoff value, particularly because the sizes of the parts and mechanisms greatly vary from one disk drive to another.

However, this method takes a long time to measure the offset, and can hardly be put to practical use.

Moreover, when the disk drive receives an impact from outside, a disk shift occurs, inevitably changing the disk runout.

This ultimately impairs the data-access ability of the disk drive.

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