Servo method and device for controlling head position for a hard disk drive

A hard disk drive comprising:

• a head for reproducing information including an MR head having a magnetoresistive effect;
• an information recording disk including a track having a servo region with servo information for identifying a track position;
• a device for reproducing the servo information from the information recording disk;
• a device for storing a correspondence between a distance information corresponding to an offset of the head from a reference position and gain information;
• a distance information derivation device for using the servo information to derive the distance information corresponding to the offset of the head from the reference position;
• and
• a feedback control device for referencing the correspondence, for reading the gain information corresponding to the derived distance information, and for using the derived gain information and the servo information to position a center of the head in a predetermined offset position relative to a center of a track.

A servo method for a hard disk drive for using a MR head that at least reproduces information and has sensitivity which is not uniform to reproduce servo information for identifying a track position from an information recording disk comprising at least one track including at least one servo region in which said servo information is stored and using the reproduced servo information and predetermined gain information to provide feedback for the control of said head to be positioned in a predetermined reference position on said track;

• wherein the correspondence between the distance information corresponding to the offset of said head from said reference position and said gain information is stored in advance;
• said reproduced servo information is used to derive the distance information corresponding to the offset of said head from said reference position;
• said correspondence is referenced to derive the gain information corresponding to the distance information obtained;
• and
• feedback control is carried out using the gain information derived and the reproduced servo information to position a center of said head in the predetermined offset position relative to a center of said track which may be said reference position.

A hard disk drive comprising:

• a head that at least reproduces information and has sensitivity, part of which is not uniform, including an MR head, having a magnetoresistive effect;
• an information recording disk comprising at least one track including at least one servo region in which said servo information for identifying a track position is stored;
• a reproduction device for reproducing said servo information from said information recording disk;
• a storage device for storing the correspondence between the distance information corresponding to the offset of said head from said reference position and gain information;
• a distance information derivation device for using said reproduced servo information to derive the distance information corresponding to the offset of a center of said head from said reference position;
• and
• a feedback control device for referencing said correspondence, reading the gain information corresponding to the distance information derived, and using the read gain information and the reproduced servo information to position the center of said head in the predetermined offset position relative to a center of said track which may be said reference position.