Granted Patent B1

US 9,047,901 · App. 13/903,197 · Granted Jun 2, 2015

Abstract

Claims (172)

1. A disk drive comprising:

a disk comprising at least a first spiral track and a second spiral track;

a head;

an actuator operable to actuate the head over the disk; and

control circuitry operable to:

measure a slope of the first spiral track at a plurality of radial locations across the disk;

generate a first spiral track error at each radial location based on a difference between the measured slope of the first spiral track and a target slope;

measure a slope of the second spiral track at a plurality of radial locations across the disk;

generate a second spiral track error at each radial location based on a difference between the measured slope of the second spiral track and the target slope; and

actuate the head over the disk based on the spiral track and the first and second spiral track errors.

2. The disk drive as recited in claim 1 , wherein the spiral track error represents a position error between the spiral track and a nominal spiral track.

3. The disk drive as recited in claim 2 , wherein the position error is generated based on:

R

^

i

=

R

^

i

-

1

+

r

·

(

s

i

+

s

i

-

1

)

/

2

s

t

;

Δ

⁢

⁢

R

i

=

(

(

i

+

1

)

·

r

)

-

R

^

i

;

i

=

1

,

2

,

…

⁢

,

N

-

2

where:

r represents a radial increment between each radial location;

s i represents the measured slope of the spiral track at radial location i;

s t represents the target slope;

{circumflex over (R)} represents a measured radial position of the head;

ΔR represents the position error; and

N represents the plurality of radial locations.

4. The disk drive as recited in claim 1 , wherein the control circuitry is further operable to interpolate the spiral track error to increase a resolution of the spiral track error.

5. The disk drive as recited in claim 2 , wherein the control circuitry is further operable to actuate the head over the disk by:

measuring a radial position of the head based on the spiral track;

adjusting the measured radial position based on the position error to generate an adjusted radial position; and

generating a control signal applied to the actuator based on the adjusted radial position.

6. The disk drive as recited in claim 5 , wherein the control circuitry is further operable to write servo data to the disk while actuating the head over the disk such that the servo data is written based on the target slope of the spiral track.

7. The disk drive as recited in claim 6 , wherein the servo data comprises servo sectors of concentric servo tracks.

8. The disk drive as recited in claim 7 , wherein the servo data comprises a spiral servo track.

9. The disk drive as recited in claim 8 , wherein the control circuitry is further operable to process the spiral servo track in order to write concentric servo sectors to the disk that define concentric servo tracks.

10. The disk drive as recited in claim 1 , wherein the target slope is predetermined.

11. The disk drive as recited in claim 1 , wherein the control circuitry is further operable to generate the target slope based on the measured slopes of the first and second spiral track.

12. A method of operating a disk drive comprising a disk comprising at least a first spiral track and a second spiral track, a head, and an actuator operable to actuate the head over the disk, the method comprising:

measuring a slope of the first spiral track at a plurality of radial locations across the disk;

generating a first spiral track error at each radial location based on a difference between the measured slope of the first spiral track and a target slope;

measuring a slope of the second spiral track at a plurality of radial locations across the disk;

generating a second spiral track error at each radial location based on a difference between the measured slope of the second spiral track and the target slope; and

actuating the head over the disk based on the spiral track and the first and second spiral track errors.

13. The method as recited in claim 12 , wherein the spiral track error represents a position error between the spiral track and a nominal spiral track.

14. The method as recited in claim 13 , wherein the position error is generated based on:

R

^

i

=

R

^

i

-

1

+

r

·

(

s

i

+

s

i

-

1

)

/

2

s

t

;

Δ

⁢

⁢

R

i

=

(

(

i

+

1

)

·

r

)

-

R

^

i

;

i

=

1

,

2

,

…

⁢

,

N

-

2

where:

r represents a radial increment between each radial location;

s i represents the measured slope of the spiral track at radial location i;

s t represents the target slope;

{circumflex over (R)} represents a measured radial position of the head;

ΔR represents the position error; and

N represents the plurality of radial locations.

15. The method as recited in claim 12 , further comprising interpolating the spiral track error to increase a resolution of the spiral track error.

16. The method as recited in claim 13 , further comprising actuating the head over the disk by:

measuring a radial position of the head based on the spiral track;

adjusting the measured radial position based on the position error to generate an adjusted radial position; and

generating a control signal applied to the actuator based on the adjusted radial position.

17. The method as recited in claim 16 , further comprising writing servo data to the disk while actuating the head over the disk such that the servo data is written based on the target slope of the spiral track.

18. The method as recited in claim 17 , wherein the servo data comprises servo sectors of concentric servo tracks.

19. The method as recited in claim 18 , wherein the servo data comprises a spiral servo track.

20. The method as recited in claim 19 , further comprising processing the spiral servo track in order to write concentric servo sectors to the disk that define concentric servo tracks.

21. The method as recited in claim 13 , wherein the target slope is predetermined.

22. The method as recited in claim 13 , further comprising generating the target slope based on the measured slopes of the first and second spiral track.

Assignments (8)