Propagation self servowrite using self-written spiral signals for in-process calibration
View Patent ↗The operation of propagation self servowrite can be improved by using spirals written upon the disk. The spirals can be used to reduce the DC drift of the propagation of the self servowrite. The writing of the spirals can be improved by using the back EMF signal for the VCM to control the velocity of the actuator during the writing of the spirals to produce a more consistent spiral shape. Additionally, back EMF crossings of the spindle can be used to space the spirals evenly about the disk.
1. A disk drive comprising:
an actuator including a write element and a read element; and
a controller to produce control signals for the actuator, the controller writing spirals on a disk of the disk drive, and propagation self servowriting on the disk, the self-servowriting propagating servo wedges using previously written servo wedges, the spirals being used to adjust the self-servo writing.
2. The disk drive of claim 1 , wherein the spirals are used to adjust DC drift in the servo wedges positioning during propagation self servowriting.
3. The disk drive of claim 1 , wherein the spiral writing includes controlling the velocity of the actuator during the writing of the spirals using the actuator back EMF as feedback.
4. The disk drive of claim 1 , wherein spacing the spirals uses spindle back EMF zero-crossings.
5. The disk drive of claim 4 , using a phase lock loop to the spindle back EMF zero-crossings.
6. A disk drive comprising:
an actuator including a write element and a read element; and
a controller to produce control signals for the actuator, the controller writing spirals on a disk of the disk drive, the spiral writing including controlling the velocity of the actuator unit during the writing of the spirals using the actuator back EMF as feedback, the controller using the spirals during self servowriting.
7. The disk drive of claim 6 , wherein the self servowriting is propagation self servowriting, the self-servowriting propagating servo wedges using previously written servo wedges, the spirals being used to adjust the self-servo writing.
8. The disk drive of claim 7 , wherein the spirals are used to adjust DC drift in the servo wedges positioning during propagation self servowriting.
9. The disk drive of claim 6 , wherein spacing the spirals uses spindle back EMF zero-crossings.
10. The disk drive of claim 6 , using a phase lock loop to the spindle back EMF zero-crossings.
11. A disk drive comprising:
an actuator including a write element and a read element; and
a controller to produce control signals for the actuator, the controller writing spirals on a disk of the disk drive, the spiral writing including spacing the spirals using spindle back EMF zero-crossings, the controller using the spirals during self servowriting.
12. The disk drive of claim 11 , wherein the self servowriting is propagation self servowriting, the self-servowriting propagating servo wedges using previously written servo wedges, the spirals being used to adjust the self-servo writing.
13. The disk drive of claim 12 , wherein the spirals are used to adjust DC drift in the servo wedges positioning during propagation self servowriting.
14. The disk drive of claim 11 , using a phase lock loop to the spindle back EMF zero-crossings.
15. The disk drive of claim 11 , wherein the spiral writing includes controlling the velocity of the actuator during the writing of the spirals using the actuator back EMF as feedback.
16. A method of servowriting a disk of a disk drive comprising:
writing spirals on a disk;
propagation self servowriting on the disk, the self-servowriting propagating servo wedges using previously written servo wedges, the spirals being used to adjust the self-servo writing.