Repeatable runout determination within a rotating media storage device
View Patent ↗A rotating media storage device (RMSD) includes a disk having at least one track with a plurality of servo wedges, a moveable head, and a microprocessor. The microprocessor receives a plurality of position error signal (PES) values during track following and sums PES values for a plurality of different sets of servo wedges of the track to generate a plurality of shifted summed position error signal (SSPES) values. The microprocessor shifts the plurality of generated SSPES values by a phase shift value to generate a plurality of corrected shifted summed position error signal (CSSPES) values, which correspond to the repeatable runout (RRO) of the disk.
1. In a rotating media storage device (RMSD), the RMSD having a disk including at least one track having a plurality of servo wedges, a moveable head, a servo control loop for controlling the position of the moveable head to perform track following, a method for repeatable runout (RRO) determination, the method comprising the steps of:
a. track following on the plurality of servo wedges of the track to obtain a plurality of position error signal (PES) values;
b. summing the PES values for a plurality of different sets of servo wedges of the track to generate a plurality of shifted summed position error signal (SSPES) values; and
c. shifting the plurality of SSPES values for the track by a phase shift value to generate a plurality of corrected shifted summed position error signal (CSSPES) values corresponding to the repeatable runout.
2. The method of claim 1 , wherein a normalization factor is applied to one of:
a. the generated SSPES values;
b. or the generated CSSPES values.
3. The method of claim 2 , wherein the normalization factor is a constant divided by one half of the total number of servo wedges of the track.
4. The method of claim 3 , wherein each set of servo wedges includes a predetermined number of servo wedges that is one half of the total number of servo wedges of the track.
5. The method of claim 4 , wherein the phase shift value is one quarter of the total number of servo wedges of the track.
6. The method of claim 3 , wherein the constant is equal to a value of approximately 1.57.
7. The method of claim 6 , wherein each set of servo wedges includes a predetermined number of servo wedges that is one quarter of the total number of servo wedges of the track.
8. The method of claim 7 , wherein the phase shift value is one eighth of the total number of servo wedges of the track.
9. The method of claim 1 , further comprising modifying the amplitude of one of the SSPES values or the CSSPES values based on an error rejection curve for the servo control loop (FIG. 8 ).
10. The method of claim 9 , wherein the error rejection curve is a predicted error rejection curve.
11. The method of claim 10 , wherein the amplitude of the one of the CSSPES values or the SSPES values is modified based on the predicted error rejection curve for a specific frequency value.
12. The method of claim 11 , wherein the specific frequency value is an integral multiple of a spindle rotational frequency.
13. The method of claim 9 , wherein the error rejection curve is a measured error rejection curve.
14. The method of claim 13 , wherein the amplitude of the one of the CSSPES values or the SSPES values is modified based on the measured error rejection curve for a specific frequency value.
15. The method of claim 14 , wherein the specific frequency value is an integral multiple of a spindle rotational frequency.
16. A rotating media storage device (RMSD), the RMSD having a disk including at least one track having a plurality of servo wedges, a moveable head, the RMSD further comprising:
a servo control loop for controlling the position of the moveable head to perform track following on a plurality of servo wedges of a track and to measure a plurality of position error signal (PES) values; and
a microprocessor under the control of a program to:
a. receive the plurality of position error signal (PES) values;
b. sum the PES values for a plurality of different sets of servo wedges of the track to generate a plurality of shifted summed position error signal (SSPES) values; and
c. shift the plurality of SSPES values for the track by a phase shift value to generate a plurality of corrected shifted summed position error signal (CSSPES) values.
17. The RMSD of claim 16 , wherein a normalization factor is applied to one of:
a. the generated SSPES values;
b. or the generated CSSPES values.
18. The RMSD of claim 17 , wherein the normalization factor is a constant divided by one half of the total number of servo wedges of the track.
19. The RMSD of claim 18 , wherein each set of servo wedges includes a predetermined number of servo wedges that is one half of the total number of servo wedges of the track.
20. The RMSD of claim 19 , wherein the phase shift value is one quarter of the total number of servo wedges of the track.
21. The RMSD of claim 18 , wherein the constant is equal to a value of approximately 1.57.
22. The RMSD of claim 21 , wherein each set of servo wedges includes a predetermined number of servo wedges that is one quarter of the total number of servo wedges of the track.
23. The RMSD of claim 22 , wherein the phase shift value is one eighth of the total number of servo wedges of the track.
24. The RMSD of claim 16 , further comprising the microprocessor modifying the amplitude of one of the SSPES values or one of the CSSPES values based on an error rejection curve for the servo control loop.
25. The RMSD of claim 24 , wherein the error rejection curve is a predicted error rejection curve.
26. The RMSD of claim 25 , wherein the amplitude of the one of the CSSPES values or the SSPES values is modified based on the predicted error rejection curve for a specific frequency value.
27. The RMSD of claim 26 , wherein the specific frequency value is an integral multiple of a spindle rotational frequency.
28. The RED of claim 24 , wherein the error rejection curve is a measured error rejection curve.
29. The RMSD of claim 28 , wherein the amplitude of the one of the CSSPES values or the SSPES values is modified based on the measured error rejection curve for a specific frequency value.
30. The RMSD of claim 29 , wherein the specific frequency value is an integral multiple of a spindle rotational frequency.
31. A computer system comprising a host computer and a rotating media storage device (RMSD), the RMSD further comprising:
a disk including at least one track having a plurality of servo wedges;
a moveable head;
a servo control loop for controlling the position of the moveable head to perform track following on a plurality of servo wedges of a track and to measure a plurality of position error signal (PES) values; and
a microprocessor under the control of a program to:
a. receive the plurality of position error signal (PES) values;
b. sum the PES values for a plurality of different sets of servo wedges of the track to generate a plurality of shifted summed position error signal (SSPES) values; and
c. shift the plurality of SSPES values for the track by a phase shift value to generate a plurality of corrected shifted summed position error signal (CSSPES) values.
32. The computer system of claim 31 , wherein a normalization factor is applied to one of:
a. the generated SSPES values;
b. or the generated CSSPES values.
33. The computer system of claim 32 , wherein the normalization factor is a constant divided by one half of the total number of servo wedges of the track.
34. The computer system of claim 33 , wherein each set of servo wedges includes a predetermined number of servo wedges that is one half of the total number of servo wedges of the track.
35. The computer system of claim 34 , wherein the phase shift value is one quarter of the total number of servo wedges of the track.
36. The computer system of claim 33 , wherein the constant is equal to a value of approximately 1.57.
37. The computer system of claim 36 , wherein each set of servo wedges includes a predetermined number of servo wedges that is one quarter of the total number of servo wedges of the track.
38. The computer system of claim 37 , wherein the phase shift value is one eighth of the total number of servo wedges of the track.
39. The computer system of claim 31 , further comprising the microprocessor modifying the amplitude of one of the SSPES values or the CSSPES values based on an error rejection curve for the servo control loop.
40. The computer system of claim 39 , wherein the error rejection curve is a predicted error rejection curve.
41. The computer system of claim 40 , wherein the amplitude of the one of the CSSPES values or the SSPES values is modified based on the predicted error rejection curve for a specific frequency value.
42. The computer system of claim 41 , wherein the specific frequency value is an integral multiple of a spindle rotational frequency.
43. The computer system of claim 39 , wherein the error rejection curve is a measured error rejection curve.
44. The computer system of claim 43 , wherein the amplitude of the one of the CSSPES values or the SSPES values is modified based on the measured error rejection curve for a specific frequency value.
45. The computer system of claim 44 , wherein the specific frequency values is an integral multiple of a spindle rotational frequency.