Disk drive writing wedge RRO data along a sinusoidal path to compensate for reader/writer offset

1. A disk drive comprising:

a disk comprising a plurality of tracks, wherein each track comprises a plurality of servo sectors comprising repeatable runout (RRO);

a head comprising a read element offset from a write element by a reader/writer offset; and

control circuitry operable to:

position the read element over a first track and the write element over a second track;

generate a first servo control signal for servoing the head in response to the servo sectors in the first track; and

write first wedge RRO data to the second track along a substantially sinusoidal path corresponding to the reader/writer offset, wherein the first wedge RRO data are for writing data to a third track,

wherein:

the control circuitry is further operable to generate the first servo control signal for servoing the head by generating first jog adjustment values to cause the write element to travel in the substantially sinusoidal path;

the control circuitry generates the first jog adjustment values in response to NF RRO values and the reader/writer offset; and

the NF RRO values represent at least one of a fundamental frequency and a harmonic frequency of the RRO.

2. The disk drive as recited in claim 1 , wherein the control circuitry is further operable to generate the first servo control signal for servoing the head by:

generating a position error signal (PES) in response to the servo sectors in the first track and the first jog adjustment values to cause the write element to travel in the substantially sinusoidal path; and

filtering the PES with a servo compensator.

3. The disk drive as recited in claim 1 , wherein the first jog adjustment values comprise feedforward compensation values.

4. The disk drive as recited in claim 3 , wherein the control circuitry is further operable to generate the first servo control signal for servoing the head by:

generating a position error signal (PES) in response to the servo sectors in the first track and the feedforward compensation values; and

filtering the PES with a servo compensator.

5. The disk drive as recited in claim 1 , wherein the control circuitry is further operable to:

position the read element over the second track;

generate second jog adjustment values to cause the read element to follow the substantially sinusoidal path;

generate a second servo control signal for servoing the head in response to the second jog adjustment values, the servo sectors in the second track, and the first wedge RRO data in the second track; and

write data to the third track.

6. The disk drive as recited in claim 1 , wherein the reader/writer offset varies based on the radial position of the head.

7. The disk drive as recited in claim 1 , wherein the control circuitry is further operable to estimate the reader/writer offset by generating a jog slope value in response to the NF RRO values.

8. The disk drive as recited in claim 7 , wherein the control circuitry is further operable to generate the first jog adjustment values by multiplying the NF RRO values by the jog slope value.

9. The disk drive as recited in claim 1 , wherein the control circuitry is further operable to write second wedge RRO data to the disk, wherein:

the second wedge RRO data are for reading data from the disk; and

the second wedge RRO data are written along a substantially circular path.

10. A method of writing wedge RRO data to a disk of a disk drive, the disk drive comprising the disk having a plurality of tracks, wherein each track comprises a plurality of servo sectors comprising repeatable runout (RRO), and a head comprising a read element offset from a write element by a reader/writer offset, the method comprising:

positioning the read element over a first track and the write element over a second track;

generating a first servo control signal for servoing the head in response to the servo sectors in the first track; and

writing first wedge RRO data to the second track along a substantially sinusoidal path corresponding to the reader/writer offset, wherein the first wedge RRO data are for writing data to a third track,

wherein:

generating the first servo control signal for servoing the head comprises generating first jog adjustment values to cause the write element to travel in the substantially sinusoidal path;

the first jog adjustment values are generated in response to NF RRO values and the reader/writer offset; and

the NF RRO values represent at least one of a fundamental frequency and a harmonic frequency of the RRO.

11. The method as recited in claim 10 , wherein generating the first servo control signal for servoing the head comprises:

generating a position error signal (PES) in response to the servo sectors in the first track and the first jog adjustment values to cause the write element to travel in the substantially sinusoidal path; and

filtering the PES with a servo compensator.

12. The method as recited in claim 10 , wherein the first jog adjustment values comprise feedforward compensation values.

13. The method as recited in claim 12 , wherein generating the first servo control signal for servoing the head comprises:

generating a position error signal (PES) in response to the servo sectors in the first track and the feedforward compensation values; and

filtering the PES with a servo compensator.

14. The method as recited in claim 10 , further comprising:

positioning the read element over the second track;

generating second jog adjustment values to cause the read element to follow the substantially sinusoidal path;

generating a second servo control signal for servoing the head in response to the second jog adjustment values, the servo sectors in the second track, and the first wedge RRO data in the second track; and

writing data to the third track.

15. The method as recited in claim 10 , wherein the reader/writer offset varies based on the radial position of the head.

16. The method as recited in claim 10 , further comprising estimating the reader/writer offset by generating a jog slope value in response to the NF RRO values.

17. The method as recited in claim 16 , wherein the first jog adjustment values are generated by multiplying the NF RRO values by the jog slope value.

18. The method as recited in claim 10 , further comprising writing second wedge RRO data to the disk, wherein:

the second wedge RRO data are for reading data from the disk; and

the second wedge RRO data are written along a substantially circular path.

19. A disk drive comprising:

a disk comprising a plurality of tracks, wherein each track comprises a plurality of servo sectors comprising repeatable runout (RRO);

a head comprising a read element offset from a write element by a reader/writer offset; and

a means for positioning the read element over a first track and the write element over a second track;

a means for generating a first servo control signal for servoing the head in response to the servo sectors in the first track; and

a means for writing first wedge RRO data to the second track along a substantially sinusoidal path corresponding to the reader/writer offset, wherein the first wedge RRO data are for writing data to a third track, wherein:

generating the first servo control signal for servoing the head comprises generating first jog adjustment values to cause the write element to travel in the substantially sinusoidal path;

the first jog adjustment values are generated in response to NF RRO values and the reader/writer offset; and

the NF RRO values represent at least one of a fundamental frequency and a harmonic frequency of the RRO.