MAGNETIC DISK DEVICE AND HEAD-POSITION CONTROL METHOD

• US 20130083424A1
• Filed: 09/07/2012
• Published: 04/04/2013
• Est. Priority Date: 09/29/2011
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: KUBOTA, Hiroshi, TAKAISHI, Kazuhiko, ABE, Takao, IWASHIRO, Masafumi
• Granted Patent: US 8,773,808 B2
• Time in Patent Office: Days
• US Class Current: 360/75
• CPC Class Codes: G11B 5/59622 Gain control; Filters

Abstract

A magnetic disk device includes a magnetic disk on which servo information is recorded, a head to read the servo information of the magnetic disk, and a position control module. When carrying out positioning control of the head, the position control module estimates frequency components of noise in a head positioning control process, using a high-order digital filter that includes first and second variable coefficients that are each based on position error information generated from the servo information read by the head.

Claims

1. A magnetic disk device comprising:

a magnetic disk on which servo information is recorded;

a head to read the servo information on the magnetic disk;

a position control module comprising a high-order adaptive digital filter containing first and second variable coefficients that are each based on position error information generated from the servo information read by the head.

2. The magnetic disk device of claim 1, wherein the position control module, at the time of carrying out positioning control of the head, integrates a first value that is obtained by multiplying, by a first factor, a second value obtained by multiplying an output value of the high-order adaptive digital filter and a third value derived from a first delayed sample of the position error information, and the first and second variable coefficients are obtained by multiplying the integrated first value with the third value.

3. The magnetic disk device of claim 2, wherein the output value of the high-order adaptive digital filter is derived from a fourth value that is obtained based on a difference between noise and the position error information.

4. The magnetic disk device of claim 3, wherein the output value of the high-order adaptive digital filter is further based on a fifth value derived from an undelayed sample of the position error information.

5. The magnetic disk device of claim 4, wherein the output value of the high-order adaptive digital filter is equal to one-half of a sum of the fourth value, the fifth value multiplied a second factor, and a sixth value that is a sum of the second variable coefficient and a seventh value, which is derived from a second delayed sample of the position error information, multiplied by a third factor.

6. The magnetic disk device of claim 5, wherein the second variable coefficient is obtained by multiplying the third value with an eighth value that is a sum of the integrated first value and a fourth factor.

7. A magnetic disk device comprising:

a magnetic disk on which servo information is recorded, a head to read the servo information on the magnetic disk, and a position control module comprising first and second high-order adaptive filters that are arranged such that an output of one is connected to an input to the other, each of first and second high-order adaptive filters containing first and second variable coefficients that are each based on the position error information generated from the servo information read by the head.

8. The magnetic disk device of claim 7, wherein

the position control module, at the time of carrying out positioning control of the head, integrates a first value that is obtained by multiplying, by a first factor, a second value obtained by multiplying an output value of the respective high-order adaptive digital filter and a third value derived from a first delayed sample of the position error information, and the first and second variable coefficients are obtained by multiplying the integrated first value with the third value.

9. The magnetic disk device of claim 8, wherein the output value of the respective high-order adaptive digital filter is derived from a fourth value that is obtained based on a difference between noise and the position error information.

10. The magnetic disk device of claim 9, wherein the output value of the respective high-order adaptive digital filter is further based on a fifth value derived from an undelayed sample of the position error information.

11. The magnetic disk device of claim 10, wherein the output value of the respective high-order adaptive digital filter is equal to one-half of a sum of the fourth value, the fifth value multiplied a second factor, and a sixth value that is a sum of the second variable coefficient and a seventh value, which is derived from a second delayed sample of the position error information, multiplied by a third factor.

12. The magnetic disk device of claim 11, wherein the second variable coefficient is obtained by multiplying the third value with an eighth value that is a sum of the integrated first value and a fourth factor.

13. A position control method in a magnetic disk device comprising a magnetic disk on which servo information is recorded, a head to read the servo information on the magnetic disk, and a high-order adaptive digital filter, the method comprising:

filtering an output value of the high-order adaptive digital filter to obtain position error information;

feeding back the position error information to the high-order adaptive digital filter; and

adjusting first and second variable coefficients of the high-order adaptive digital filter based on noise and the position error information that was fed back.

14. The position control method of claim 13, wherein a first value that is obtained by multiplying, by a first factor, a second value obtained by multiplying the output value of the high-order adaptive digital filter and a third value derived from a first delayed sample of the position error information is integrated, and wherein the first and the second variable coefficients are obtained by multiplying the integrated first value with the third value.

15. The position control method of claim 14, wherein the output value of the high-order adaptive digital filter is derived from a fourth value that is obtained based on a difference between noise and the position error information.

16. The position control method of claim 15, wherein the output value of the high-order adaptive digital filter is further based on a fifth value derived from an undelayed sample of the position error information.

17. The position control method of claim 16, wherein the output value of the high-order adaptive digital filter is equal to one-half of a sum of the fourth value, the fifth value multiplied a second factor, and a sixth value that is a sum of the second variable coefficient and a seventh value, which is derived from a second delayed sample of the position error information, multiplied by a third factor.

18. The position control method of claim 17, wherein the second variable coefficient is obtained by multiplying the third value with an eighth value that is a sum of the integrated first value and a fourth factor.