Adjusting track width to compensate for offset writing of a track
View Patent ↗An offset from track center of a writer that is writing to a track of a magnetic recording medium is determined. A write current applied to a write coil of the writer is adjusted to compensate for the offset. The adjusting of the write current affects a width of the track.
1. A method, comprising:
positioning a read/write head over a track of a magnetic recording medium via a voice coil motor and a microactuator;
determining an offset from track center of a writer of the read/write head that is writing to the track via a servo feedback signal from a reader of the read/write head; and
based on a high frequency part of the servo feedback signal, adjusting a write current applied to a write coil of the writer to compensate for the offset, the adjusting of the write current affecting a width of the track, a low frequency part of the feedback signal being used to control the microactuator.
2. The method of claim 1 , wherein the writer is writing shingled tracks to the magnetic recording medium.
3. The method of claim 1 , wherein adjusting the write current comprises changing a DC level of the write current.
4. The method of claim 1 , wherein adjusting the write current comprises changing one or more of an overshoot magnitude of the write current and an overshoot duration of the write current.
5. The method of claim 1 , wherein the offset is caused by a repeatable runout, and wherein a previously measured value of the repeatable runout is used to determine the offset from track center.
6. The method of claim 1 , wherein adjusting the write current to affect the width of the track comprises using a thermal sensor to compensate for write width changes due to temperature.
7. The method of claim 1 , wherein the writer operates in an open servo control loop mode, and the microactuator and the voice coil motor operate in a closed servo control loop mode.
8. An apparatus comprising:
interface circuitry configured to:
write to a track of a magnetic recording medium via a writer of a read/write head;
read a servo feedback signal from a reader of the read/write head that indicates a position of the read/write head over the track; and
position the read/write head over tracks of the magnetic recording medium via control signals sent to a voice coil motor and a microactuator; and
a controller coupled to the interface circuitry and configured to:
determine an offset from track center of the track as it is written based on the servo feedback signal, a low frequency part of the servo feedback signal being used to control at least the microactuator; and
based on a high frequency part of the servo feedback signal, adjust a width of the track to compensate for the offset.
9. The apparatus of claim 8 , wherein the magnetic writer is writing shingled tracks to the magnetic recording medium.
10. The apparatus of claim 8 , wherein adjusting the width of the track comprises adjusting a write current applied to a write coil of the writer.
11. The apparatus of claim 10 , wherein adjusting the write current comprises changing one or more of a DC level, an overshoot magnitude, and an overshoot duration of the write current.
12. The apparatus of claim 8 , wherein the recording medium comprises a heat-assisted magnetic recording medium, and adjusting the width of the track comprises adjusting a laser power used to heat the heat-assisted magnetic recording medium.
13. The apparatus of claim 8 , wherein the offset is caused by a repeatable runout, and wherein a previously measured value of the repeatable runout is used to determine the offset from track center.
14. The apparatus of claim 10 , wherein adjusting the write current to affect the width of the track comprises using a thermal sensor to compensate for write width changes due to temperature.
15. The apparatus of claim 8 , wherein the writer operates in an open servo control loop mode, and the microactuator and the voice coil motor operate in a closed servo control loop mode.
16. A method, comprising:
positioning a read/write head over a track of a heat-assisted magnetic recording medium via a voice coil motor and a microactuator;
determining an offset from track center of a writer of the read/write head that is writing to the track via a servo feedback signal from a reader of the read/write head; and
based on a high frequency part of the servo feedback signal, adjusting a laser power applied to a laser of the writer to compensate for the offset, the adjusting of the laser power affecting a width of the track, a low frequency part of the servo feedback signal being used to control the microactuator.
17. The god of claim 16 , wherein the writer is writing shingled tracks to the recording medium.
18. The method of claim 16 , wherein the offset is caused by a repeatable runout, and wherein a previously measured value of the repeatable runout is used to determine the offset from track center.
19. The method of claim 16 , wherein the servo feedback signal is further used to control the voice coil motor.
20. The method of claim 16 , wherein the writer operates in an open servo control loop mode, and the microactuator and the voice coil motor operate in a closed servo control loop mode.