Disk drive adjusting fly height actuator to compensate for laser induced head protrusion in heat assisted magnetic recording
View Patent ↗A disk drive is disclosed comprising a head actuated over a disk, wherein the head comprises a laser operable to heat the disk while writing data to the disk, and a fly height actuator (FHA) operable to adjust a fly height of the head over the disk. When a write command is received to write data to a target data track, the head is positioned over the target data track. When the head approaches a target data sector of the target data track, a power applied to the FHA is increased to decrease the fly height of the head. When the head reaches the target data sector, a power applied to the laser is increased to heat the disk, and the power applied to the FHA is decreased substantially monotonically while writing data to the target data sector.
1. A disk drive comprising:
a disk comprising a plurality of data tracks defined by servo sectors, wherein each data track comprises a plurality of data sectors;
a head actuated over the disk, wherein the head comprises a laser operable to heat the disk while writing data to the disk and a fly height actuator (FHA) operable to adjust a fly height of the head over the disk; and
control circuitry operable to:
receive a write command to write data to a target data track;
position the head over the target data track;
when the head approaches a target data sector of the target data track, increase a power applied to the FHA to decrease the fly height of the head; and
when the head reaches the target data sector, increase a power applied to the laser to heat the disk, and decrease substantially monotonically the power applied to the FHA while writing data to the target data sector.
2. The disk drive as recited in claim 1 , wherein the control circuitry is further operable to decrease substantially monotonically the power applied to the fly height actuator based on a function comprising at least one exponential.
3. The disk drive as recited in claim 1 , wherein the control circuitry is further operable to decrease substantially monotonically the power applied to the FHA prior to the head reaching the target data sector.
4. The disk drive as recited in claim 1 , wherein the control circuitry is further operable to:
decrease the power applied to the laser after writing the data to the target data track; and
after decreasing the power applied to the laser, increase substantially monotonically the power applied to the FHA.
5. The disk drive as recited in claim 4 , wherein the control circuitry is further operable to increase substantially monotonically the power applied to the FHA based on a function comprising at least one exponential.
6. The disk drive as recited in claim 4 , wherein after decreasing the power applied to the laser the control circuitry is operable to:
increase the power applied to the FHA by a step increment; and
after increasing the power applied to the FHA by the step increment, increase substantially monotonically the power applied to the FHA.
7. The disk drive as recited in claim 6 , wherein the control circuitry is further operable to increase substantially monotonically the power applied to the FHA based on a function comprising at least one exponential.
8. A method of operating a disk drive, the disk drive comprising a head actuated over a disk comprising a plurality of data tracks defined by servo sectors, wherein each data track comprises a plurality of data sectors, and the head comprises a laser operable to heat the disk while writing data to the disk and a fly height actuator (FHA) operable to adjust a fly height of the head over the disk, the method comprising:
receiving a write command to write data to a target data track;
positioning the head over the target data track;
when the head approaches a target data sector of the target data track, increasing a power applied to the FHA to decrease the fly height of the head; and
when the head reaches the target data sector, increasing a power applied to the laser to heat the disk, and decreasing substantially monotonically the power applied to the FHA while writing data to the target data sector.
9. The method as recited in claim 8 , further comprising decreasing substantially monotonically the power applied to the FHA based on a function comprising at least one exponential.
10. The method as recited in claim 8 , further comprising decreasing substantially monotonically the power applied to the FHA prior to the head reaching the target data sector.
11. The method as recited in claim 8 , further comprising:
decreasing the power applied to the laser after writing the data to the target data track; and
after decreasing the power applied to the laser, increasing substantially monotonically the power applied to the FHA.
12. The method as recited in claim 11 , further comprising increasing substantially monotonically the power applied to the FHA based on a function comprising at least one exponential.
13. The method as recited in claim 11 , wherein after decreasing the power applied to the laser further comprising:
increasing the power applied to the FHA by a step increment; and
after increasing the power applied to the FHA by the step increment, increasing substantially monotonically the power applied to the FHA.
14. The method as recited in claim 13 , further comprising increasing substantially monotonically the power applied to the FHA based on a function comprising at least one exponential.