Method for improved repeatable runout learning in a disk drive
A method is disclosed for adaptive learning of fundamental-frequency repeatable runout (1FRRO) compensation information in a disk drive. The disk drive includes a transducer head, a magnetic disk having a plurality of concentric data tracks defined by embedded servo wedges that provide position information, and a control system. In the method, 1FRRO compensation information is learned over a predetermined minimum number of disk revolutions. After the predetermined minimum number of disk revolutions, the 1FRRO compensation information is monitored for convergence while learning of the 1FRRO compensation information continues. Learning is terminated upon detection of convergence of the 1FRRO compensation information.
1. A method for adaptive fundamental-frequency repeatable runout (1FRRO) learning in a disk drive to reduce learn time, comprising:
learning 1FRRO compensation information over a predetermined minimum number of disk revolutions;
after the predetermined minimum number of disk revolutions, monitoring the 1FRRO compensation information for convergence while continuing learning of the 1FRRO compensation information; and
terminating learning upon detection of convergence of the 1FRRO compensation information.
2. A method for adaptive fundamental-frequency repeatable runout (1FRRO) learning as defined in claim 1 , wherein the predetermined minimum number of disk revolutions is equal to or greater than 2.
3. A method for adaptive fundamental-frequency repeatable runout (1FRRO) learning as defined in claim 2 , wherein the predetermined minimum number of disk revolutions is less than 12.
4. A method for adaptive fundamental-frequency repeatable runout (1FRRO) learning as defined in claim 1 , wherein the predetermined minimum number of disk revolutions is equal to 5.
5. A method for adaptive fundamental-frequency repeatable runout (1FRRO) learning as defined in claim 1 , wherein the step of monitoring the 1FRRO compensation information for convergence while continuing learning of the 1FRRO compensation information comprises at least one disk revolution.
6. A method for adaptive fundamental-frequency repeatable runout (1FRRO) learning as defined in claim 1 , wherein the learning steps are performed after each disk drive power-on.
7. A method for adaptive fundamental-frequency repeatable runout (1FRRO) learning as defined in claim 1 , wherein the learning steps are performed after detection of a shock event.
8. A method for adaptive fundamental-frequency repeatable runout (1FRRO) learning as defined in claim 1 , wherein the detection of convergence of the 1FRRO compensation information comprises:
initializing convergence monitoring values R and I;
updating the convergence monitoring values according to the formulas:
R=R +PES*cos(2 πi/N )
I=I +PES*sin(2 πi/N )
where:
i is an index representing one of N servo sectors;
PES is position error signal;
calculating a convergence value according to the formula:
DFT=DFT +( R 2 +I 2 ) 1/2 ;
comparing the convergence value to a threshold to detect convergence of the 1FRRO compensation information.
9. A method for adaptive fundamental-frequency repeatable runout (1FRRO) learning as defined in claim 1 , further comprising concurrently learning and monitoring harmonic-frequency repeatable runout (nFRRO) compensation information for convergence; and terminating learning of the nFRRO compensation information upon detection of convergence of the nFRRO compensation information.
10. A disk drive, comprising:
a disk having a plurality of concentric data tacks defined by embedded servo wedges, the disk having some eccentricity exhibiting fundamental frequency runout (1FRRO); and
a control system operable to:
learn 1FRRO compensation information over a predetermined minimum number of disk revolutions;
after the predetermined minimum number of disk revolutions, monitor the 1FRRO compensation information for convergence while continuing to learn the 1FRRO compensation information; and
terminate learning upon detection of convergence of the 1FRRO compensation information.
11. A disk drive as defined in claim 10 , wherein the predetermined minimum number of disk revolutions is equal to or greater than 2.
12. A disk drive as defined in claim 11 , wherein the predetermined minimum number of disk revolutions is less than 12.
13. A disk drive as defined in claim 10 , wherein the predetermined minimum number of disk revolutions is equal to 5.
14. A disk drive as defined in claim 10 , wherein the control system monitors the 1FRRO compensation information for convergence while continuing to learn the 1FRRO compensation information for at least one disk revolution.
15. A disk drive as defined in claim 10 , wherein the control system learns the 1FRRO compensation information after each disk drive power-on.
16. A disk drive as defined in claim 10 , wherein the control system learns the 1FRRO compensation information after detection of a shock event.
17. A disk drive as defined in claim 10 , wherein the detection of convergence of the 1FRRO compensation information comprises:
initializing convergence monitoring values R and I;
updating the convergence monitoring values according to the formulas:
R=R +PES*cos(2 πi/N )
I=I +PES*sin(2 πi/N )
where:
i is an index representing one of N servo sectors;
PES is position error signal;
calculating a convergence value according to the formula:
DFT=DFT +( R 2 +I 2 ) 1/2 ;
comparing the convergence value to a threshold to detect convergence of the 1FRRO compensation information.
18. A disk drive as defined in claim 10 , wherein the control system is further operatable to concurrently learn and monitor harmonic-frequency repeatable runout (nFRRO) compensation information for convergence; and terminate learning of the nFRRO compensation information upon detection of convergence of the nFRRO compensation information.
19. A disk drive with adaptive fundamental-frequency repeatable runout (1FRRO) learning to reduce learn time, comprising:
means for learning 1FRRO compensation information over a predetermined minimum number of disk revolutions;
means for monitoring, after the predetermined minimum number of disk revolutions, the 1FRRO compensation information for convergence while continuing learning of the 1FRRO compensation information; and
means for terminating learning upon detection of convergence of the 1FRRO compensation information.
20. A disk drive as defined in claim 19 , wherein the predetermined minimum number of disk revolutions is equal to or greater than 2.
21. A disk drive as defined in claim 20 , wherein the predetermined minimum number of disk revolutions is less than 12.
22. A disk drive as defined in claim 19 , wherein the predetermined minimum number of disk revolutions is equal to 5.