Magnetic recording disk drive with write position error signal values written in the data tracks for compensation of track misregistration

Patent metadata

Field	Value
Publication number	US-9437232-B1
Application number	US-201514800444-A
Country	US
Kind code	B1
Filing date	Jul 15, 2015
Priority date	Jul 15, 2015
Publication date	Sep 6, 2016
Grant date	Sep 6, 2016

Abstract

A hard disk drive is adapted to take the most recent estimated read head positions (the position error signal or PES values) that are obtained during writing and write those values into the data sectors as written PES (WPES) values. The WPES values are available on readback for use as a predictor of the positions in which subsequent data sectors were written and are also available for use in a data recovery procedure should a particular data sector fail to be recovered. In two-dimensional magnetic recording, the difference between the WPES value and the read PES value is a quantity required to rapidly select the best 2D equalizer. The PES values may be encoded prior to being written into the data sectors. The WPES values are appended to the data sectors after the preamble and sync fields, which occur after every servo sector.

First claim

What is claimed is:

1. A magnetic recording disk drive comprising;
a magnetic recording disk comprising
a plurality of radially spaced data tracks, the data tracks including data sectors;
a plurality of radially spaced servo tracks having a plurality of angularly spaced servo sectors extending across the servo tracks and data tracks, the servo sectors containing position error signal (PES) blocks;

at least one read head for reading data from the data tracks and PES blocks from the servo tracks;
a write head for writing to the data tracks;
a head carrier supporting the read head and write head;
an actuator connected to the carrier for moving the read and write heads radially across the disk;
read/write electronics coupled to the read head and write head for decoding the PES blocks read by the read head into PES values and for causing data to be written into the data sectors by the write head, the read/write electronics being adapted to cause the write head to write PES values into the data tracks when writing data into the data sectors; and
servo electronics coupled to the actuator for adjusting the radial position of the read head in a data track in response to the written PES values (WPES values) read by the read head.

2. The disk drive of claim 1 wherein the read/write electronics is adapted to cause the write head to write the WPES values together with the data in the data sectors.

3. The disk drive of claim 1 further comprising an encoder for encoding the PES values prior to writing the PES values as WPES values and a decoder for decoding the encoded WPES values.

4. The disk drive of claim 3 wherein the encoder is adapted to encode a code selected from a repetition code, a Reed-Muller code and a combination of a repetition code and a Reed-Muller code, and the decoder is adapted to decode said selected code.

5. The disk drive of claim 3 wherein the read/write electronics is adapted to append the encoded WPES values to the data sectors.

6. The disk drive of claim 5 wherein the read/write electronics is adapted to append the encoded WPES values at the beginning of the data sectors.

7. The disk drive of claim 5 wherein a preamble field and a sync field are located immediately after each servo sector and wherein the read/write electronics is adapted to append the encoded WPES values immediately after the preamble field and sync field.

8. The disk drive of claim 1 wherein the read/write electronics is adapted to cause the write head to write a WPES value in response to each servo sector read by the read head.

9. The disk drive of claim 1 wherein the servo electronics is adapted to cause the read head to follow a data track by modifying the PES values decoded from the PES blocks in the servo sectors with the WPES values read from the data track.

10. The disk drive of claim 1 wherein the disk drive is a shingled magnetic recording disk drive, wherein the write head has a cross-track width greater than the cross-track width of the read head and the disk has overlapping data tracks, and wherein the read/write electronics is adapted to cause the write head to write PES values into adjacent overlapping data tracks in succession in a first radial direction, and to cause the read head to read the WPES values from adjacent overlapping data tracks in succession in a radial direction opposite said first radial direction.

11. The disk drive of claim 1 wherein the disk drive is a two-dimensional magnetic recording (TDMR) disk drive and wherein the servo electronics is adapted to calculate, from the PES values decoded from the PES blocks and the WPES values, the offset of the read heads from a data track centerline.

12. The disk drive of claim 1 wherein the servo electronics includes a processor for running a servo control loop that receives the decoded PES values from the PES blocks read by the read head from the servo sectors and outputs read head position to the actuator, wherein the processor is adapted to modify said read head position in response to WPES values read by the read head from the data tracks.

13. A two-dimensional magnetic recording (TDMR) disk drive comprising;
a magnetic recording disk comprising
a plurality of radially spaced data tracks, the data tracks including data sectors;
a plurality of radially spaced servo tracks having a plurality of angularly spaced servo sectors extending across the servo tracks and data tracks, the servo sectors containing position error signal (PES) blocks;

two read heads for reading data from the data tracks, at least one of the read heads adapted to read PES blocks from the servo tracks;
a write head for writing to the data sectors;
a head carrier supporting the read heads and write head;
an actuator connected to the carrier for moving the read heads and write head radially across the disk;
read/write electronics coupled to the read heads and write head for causing data to be written into the data sectors of a data track by the write head and for decoding the PES blocks read by said at least one read head from a first servo track into PES values while the write head is writing data in the data sectors of said data track, the read/write electronics adapted to cause the write head to write said PES values (WPES values) into the data sectors when writing data into the data sectors of said data track;
an encoder for encoding the PES values into encoded WPES values prior to causing the WPES values to be written into the data sectors of said data track;
a decoder for decoding the encoded WPES values read by the read heads from the data sectors of said data track; and
servo electronics coupled to the actuator for moving said at least one read head to a second servo track prior to reading data sectors from said data track, the servo electronics adapted to adjust the radial position of said at least one read head relative to said second servo track when reading said data track in response to the difference between the decoded WPES values from the data sectors in said data track and the PES values decoded from the PES blocks in said second servo track.

14. The disk drive of claim 13 wherein the encoder is adapted to encode a code selected from a repetition code, a Reed-Muller code and a combination of a repetition code and a Reed-Muller code, and the decoder is adapted to decode said selected code.

15. The disk drive of claim 13 wherein the read/write electronics is adapted to append the encoded WPES values to the data sectors.

16. The disk drive of claim 15 wherein the read/write electronics is adapted to append the encoded WPES values at the beginning of the data sectors.

17. The disk drive of claim 15 wherein a preamble field and a sync field are located immediately after each servo sector and wherein the read/write electronics is adapted to append the encoded WPES values immediately after the preamble field and sync field.

18. The disk drive of claim 13 wherein the read/write electronics is adapted to cause the write head to write a WPES value in response to each servo sector read by the read head.

19. The disk drive of claim 13 wherein the TDMR disk drive is a shingled magnetic recording disk drive, wherein the write head has a cross-track width greater than the cross-track width of the read head and the disk has overlapping data tracks.

20. The disk drive of claim 13 wherein the servo electronics is adapted to calculate, from the PES values decoded from the PES blocks and the decoded WPES values, the offset of the read heads from a data track centerli

Assignees

• HGST Netherlands BV

Inventors

• Galbraith Richard Leo
• Hanson Weldon Mark
• Wood Roger William

Classifications

• G11B5/59688

  Servo signal format patterns or signal processing thereof, e.g. dual, tri, quad, burst signal patterns · CPC title

• G11B5/59627 Primary

  Aligning for runout, eccentricity or offset compensation (G11B5/5534, G11B5/59677, G11B5/59688 take precedence) · CPC title

• G11B5/59672

  Servo re-writing, e.g. for the correction of offsets or 'fading' of servo marks · CPC title

• G11B5/012

  Recording on, or reproducing or erasing from, magnetic disks (G11B17/00, G11B19/00 take precedence) · CPC title