Compensation for nonlinearity in servo patterns

1. A method, comprising:

generating a y-position estimate based on a servo readback signal;

determining a nonlinearity-correction value corresponding to the y-position estimate by interpolation using nonlinearity-correction values corresponding to known locations in a vicinity of the estimated y-position; and

adjusting the y-position estimate using the nonlinearity-correction value.

2. The method as recited in claim 1 , wherein determining the nonlinearity-correction value corresponding to the y-position estimate includes retrieving the nonlinearity-correction value from a table.

3. The method as recited in claim 1 , wherein determining the nonlinearity-correction value corresponding to the y-position estimate includes retrieving the nonlinearity-correction value from a source selected from the group consisting of: a magnetic tape cartridge memory, data stored on a magnetic tape, and a magnetic tape library memory.

4. The method as recited in claim 1 , wherein the nonlinearity-correction value is determined by using a function for directly computing the nonlinearity-correction value as a function of the y-position estimate.

5. The method as recited in claim 1 , comprising:

generating a second y-position estimate based on a second servo readback signal;

determining a second nonlinearity-correction value corresponding to the second y-position estimate; and

adjusting the second y-position estimate using the second nonlinearity-correction value.

6. A computer program product for compensating for nonlinearity in a timing based servo pattern, the computer program product comprising a computer readable storage medium having program instructions embodied therewith, the program instructions readable and/or executable by a controller to cause the controller to:

generate, by the controller, a y-position estimate based on a servo readback signal;

determine, by the controller, a nonlinearity-correction value corresponding to the y-position estimate by using a function for directly computing the nonlinearity-correction value as a function of the y-position estimate; and

adjust, by the controller, the y-position estimate using the nonlinearity-correction value.

7. The computer program product as recited in claim 6 , wherein determining the nonlinearity-correction value corresponding to the y-position estimate includes retrieving the nonlinearity-correction value from a table.

8. The computer program product as recited in claim 6 , wherein the nonlinearity-correction value is determined by interpolation using nonlinearity-correction values corresponding to known locations in a vicinity of the estimated y-position.

9. The computer program product as recited in claim 6 , the program instructions readable and/or executable by the controller to cause the controller to:

generate, by the controller, a second y-position estimate based on a second servo readback signal;

determine, by the controller, a second nonlinearity-correction value corresponding to the second y-position estimate; and

adjust, by the controller, the second y-position estimate using the second nonlinearity-correction value.

10. An apparatus, comprising:

a controller configured to:

generate a y-position estimate based on a servo readback signal;

determine a nonlinearity-correction value corresponding to the y-position estimate,

wherein determining the nonlinearity-correction value corresponding to the y-position estimate includes retrieving the nonlinearity-correction value from a table,

wherein the table includes a plurality of nonlinearity-correction values corresponding to known locations relative to a servo band,

wherein the servo readback signal includes a signal from a servo reader reading the servo band; and

adjust the y-position estimate using the nonlinearity-correction value.

11. The apparatus as recited in claim 10 , wherein determining the nonlinearity-correction value corresponding to the y-position estimate includes retrieving the nonlinearity-correction value from a source selected from the group consisting of: a magnetic tape cartridge memory, data stored on a magnetic tape, and a magnetic tape library memory.

12. The apparatus as recited in claim 10 , wherein the nonlinearity-correction value corresponding to the y-position estimate is determined by interpolation using nonlinearity-correction values corresponding to known locations in a vicinity of the estimated y-position.

13. The apparatus as recited in claim 10 , wherein the nonlinearity-correction value is determined by using a function for directly computing the nonlinearity-correction value as a function of the y-position estimate.

14. The apparatus as recited in claim 10 , wherein the controller is further configured to:

generate a second y-position estimate based on a second servo readback signal;

determine a second nonlinearity-correction value corresponding to the second y-position estimate; and

adjust the second y-position estimate using the second nonlinearity-correction value.

15. The apparatus as recited in claim 14 , wherein the nonlinearity-correction value is determined by using a function for directly computing the nonlinearity-correction value as a function of the y-position estimate, wherein the second nonlinearity-correction value is determined by using a second function for directly computing the nonlinearity-correction value as a function of the second y-position estimate, wherein the function and second functions are different.

16. The apparatus as recited in claim 10 , the controller is configured to: use the adjusted y-position estimate for adjusting a head position of a magnetic tape head thereafter reading a servo band, wherein the servo readback signal includes a signal from a servo reader of the magnetic tape head reading the servo band.