Data storage device servoing heads based on virtual servo tracks
View Patent ↗A data storage device is disclosed comprising a first disk surface comprising servo tracks defined by servo sectors and recorded at a first radial density, and a first head actuated over the first disk surface. A servo sector on the first disk surface is read to generate a first physical position measurement that is converted into a first virtual position measurement corresponding to a nominal radial density of servo tracks different from the first radial density. The first head is servoed over the first disk surface based on the first virtual position measurement.
1. A data storage device comprising:
a first disk surface comprising servo tracks defined by servo sectors and recorded at a first radial density;
a first head actuated over the first disk surface; and
control circuitry configured to:
read a servo sector on the first disk surface to generate a first physical position measurement;
first convert the first physical position measurement into a first virtual position measurement corresponding to a nominal radial density of servo tracks different from the first radial density; and
servo the first head over the first disk surface based on the first virtual position measurement.
2. The data storage device as recited in claim 1 , further comprising:
a second disk surface comprising servo tracks defined by servo sectors and recorded at a second radial density different from the first radial density; and
a second head actuated over the second disk surface;
wherein the control circuitry is further configured to:
read a servo sector on the second disk surface to generate a second physical position measurement;
second convert the second physical position measurement into a second virtual position measurement corresponding to the nominal radial density, wherein the second radial density is different from the nominal radial density; and
servo the second head over the second disk surface based on the second virtual position measurement.
3. The data storage device as recited in claim 1 , wherein the control circuitry is further configured to first convert the first physical position measurement into the first virtual position measurement based on a first conversion function.
4. The data storage device as recited in claim 2 , wherein the control circuitry is further configured to second convert the second physical position measurement into the second virtual position measurement based on a second conversion function.
5. The data storage device as recited in claim 2 , wherein when the first head and the second head are both positioned at a first radial location:
the first physical position measurement substantially equals the second physical position measurement; and
the first virtual position measurement substantially equals the second virtual position measurement.
6. The data storage device as recited in claim 5 , wherein at the first radial location the first virtual position measurement and the second virtual position measurement identify a boundary servo track.
7. The data storage device as recited in claim 5 , wherein the control circuitry is further operable to read at least one parameter for the first conversion and the second conversion from at least one of the first disk surface and the second disk surface at the first radial location.
8. The data storage device as recited in claim 5 , wherein when the first head and the second head are both positioned at a second radial location:
the first physical position measurement does not equal the second physical position measurement; and
the first virtual position measurement substantially equals the second virtual position measurement.
9. The data storage device as recited in claim 8 , wherein:
the servo tracks of the first and second disk surfaces are grouped to define servo zones;
a servo data rate of each servo zone varies across the servo zones; and
the second radial location defines a servo zone boundary between servo zones on both the first and second disk surface.
10. The data storage device as recited in claim 9 , wherein the control circuitry is further configured to servo write the servo sectors on the first disk surface and the second disk surface such that the second radial location defines the servo zone boundary.
11. The data storage device as recited in claim 1 , wherein:
when the first head is positioned at a first radial location the first physical position measurement substantially equals the first virtual position measurement; and
when the first head is positioned at a second radial location the first physical position measurement does not equal the first virtual position measurement.
12. The data storage device as recited in claim 11 , wherein at the first radial location the first virtual position measurement identifies a boundary servo track.
13. The data storage device as recited in claim 11 , wherein the control circuitry is further operable to read at least one parameter for the first conversion from the first disk surface at the first radial location.
14. A method of operating a data storage device, the method comprising:
reading a servo sector on a first disk surface to generate a first physical position measurement;
first converting the first physical position measurement into a first virtual position measurement corresponding to a nominal radial density of servo tracks different from a first radial density of servo tracks on the first disk surface; and
servoing a first head over a first disk surface based on the first virtual position measurement.
15. The method as recited in claim 14 , further comprising:
reading a servo sector on a second disk surface to generate a second physical position measurement;
second converting the second physical position measurement into a second virtual position measurement corresponding to the nominal radial density of servo tracks, wherein a second radial density of servo tracks recorded on the second disk surface is different from the first radial density; and
servo a second head over a second disk surface based on the second virtual position measurement.
16. The method as recited in claim 14 , further comprising first converting the first physical position measurement into the first virtual position measurement based on a first conversion function.
17. The method as recited in claim 15 , further comprising second converting the second physical position measurement into the second virtual position measurement based on a second conversion function.
18. The method as recited in claim 15 , wherein when the first head and the second head are both positioned at a first radial location:
the first physical position measurement substantially equals the second physical position measurement; and
the first virtual position measurement substantially equals the second virtual position measurement.
19. The method as recited in claim 18 , wherein at the first radial location the first virtual position measurement and the second virtual position measurement identify a boundary servo track.
20. The method as recited in claim 18 , further comprising reading at least one parameter for the first conversion and the second conversion from at least one of the first disk surface and the second disk surface at the first radial location.
21. The method as recited in claim 18 , wherein when the first head and the second head are both positioned at a second radial location:
the first physical position measurement does not equal the second physical position measurement; and
the first virtual position measurement substantially equals the second virtual position measurement.
22. The method as recited in claim 18 , wherein:
the servo tracks of the first and second disk surfaces are grouped to define servo zones;
a servo data rate of each servo zone varies across the servo zones; and
the second radial location defines a servo zone boundary between servo zones on both the first and second disk surface.
23. The method as recited in claim 22 , further comprising servo writing the servo tracks on the first disk surface and the second disk surface such that the second radial location defines the servo zone boundary.
24. The method as recited in claim 14 , wherein:
when the first head is positioned at a first radial location the first physical position measurement substantially equals the first virtual position measurement; and
when the first head is positioned at a second radial location the first physical position measurement does not equal the first virtual position measurement.
25. The method as recited in claim 24 , wherein at the first radial location the first virtual position measurement identifies a boundary servo track.
26. The method as recited in claim 24 , further comprising reading at least one parameter for the first conversion from the first disk surface at the first radial location.