Controller selection to reduce written-in run-out

1. A system comprising:

a servo controller configured to select and employ a controller from a plurality of controllers, where the selected controller produces a least amount of written-in run-out error among the plurality of controllers; and

a mode selector that is configured to receive outputs of the plurality of controllers and to generate an actuator control signal in response to a contribution of the outputs of at least two of the plurality of controllers that are operating in parallel, wherein the mode selector is configured to provide a continuous transition between outputs of the at least two of the controllers.

2. The system of claim 1 , wherein the controller selected is used for writing servo information in a disk drive.

3. The system of claim 2 ,

wherein the system is operable for use with the disk drive, the disk drive having a disk, and

wherein the least amount of written-in-run-out error appears in servo tracks of the disk.

4. The system of claim 1 , wherein each of the controllers is optimized based on a respective disturbance signature associated with each respective controller.

5. The system of claim 1 , wherein the respective amount of written-in run-out error of each of the controllers is computed by applying a cost function.

6. The system of claim 1 , further comprising one or more disks wherein the selected controller is employed with one of the one or more disks.

7. The system of claim 1 , further comprising one or more disks wherein the selected controller is employed with all of the one or more disks.

8. The system of claim 1 , wherein the servo controller is a self-servo writing controller.

9. The system of claim 1 ,

wherein the servo controller is configured to determine the written-in run-out error produced by each of the controllers, and

wherein the selected controller corresponds to the controller determined to produce the least written-in run-out error among the controllers.

10. The system of claim 1 ,

wherein the system is operable for use with a disk drive, and

wherein each of the controllers is configured to process a position error signal (PES) and selectively output a control signal, based on the PES, to an actuator of the disk drive.

11. The system of claim 10 ,

wherein the servo controller is configured to provide to the actuator the control signal of the selected controller, free of the respective control signals of the one or more other controllers of the controllers.

12. The system of claim 1 , wherein the least amount of written-in run-out error is produced by the selected controller in servo data written by the selected controller.

13. The system of claim 1 , wherein the mode selector is further configured to increase a contribution in the actuator control signal of the output of the selected controller and to decrease a contribution in the actuator control signal of a non-selected controller in response to a position error signal to thereby provide a continuous transition in the actuator control signal.

14. The system of claim 1 , wherein the mode selector is configured to delay a transition between outputs of a non-selected controller and the selected controller until a transducer operatively controlled by the servo controller is moved between tracks in a seek operation.

15. A method comprising:

providing a plurality of controllers operating in parallel; and

selecting a controller from the controllers producing a least expected amount of written-in run out error among the controllers; and

smoothly transitioning between an output of a first one of the controllers to the selected one of the controllers to provide a continuous control signal in response to contributions of the outputs of at least two of the plurality of controllers operating in parallel.

16. A method according to claim 15 , further comprising:

determining a position error produced by each of the controllers in writing servo data, wherein the selected controller produces the lowest determined position error among the controllers.

17. The method of claim 16 , wherein determining the position error produced by each of the controllers comprises performing a fast Fourier transform.

18. A method according to claim 15 further comprising:

calculating a cost function for each of the controllers, wherein the selected controller has the lowest calculated cost of the controllers.

19. The method of claim 15 , wherein the selected controller is employed to write servo data.

20. The method of claim 15 , wherein each of the controllers is optimized for a respective disturbance signature.

21. The method of claim 15 , wherein said selecting is performed with respect to each disk in a disk drive.

22. The method of claim 15 , wherein said selecting is performed with respect to all disks in a disk drive.

23. The method of claim 15 , wherein the method is performed during a self-servo write process.

24. A system operable for use with a plurality of disk controllers, the system comprising:

determining means for determining an amount of written-in run-out error produced by each of the disk controllers wherein the disk controllers are operating in parallel;

servo controller means for employing and selecting a disk controller corresponding to the disk controller determined to produce the least amount of written-in run-out error among the controllers; and

mode selection means for receiving outputs of the plurality of disk controllers and for generating an actuator control signal in response to a contribution of the outputs of at last two of the plurality of controllers that are operating in parallel, wherein the mode selection means is configured to provide a continuous transition between outputs of the at least two of the controllers.

25. The system of claim 24 , wherein the determined amount of written-in run-out is computed using a cost function.

26. The system of claim 24 , wherein the servo controller means is a self-servo writing controller.