Method and apparatus for canceling repeatable run-out errors in positioning on recording medium
A method and apparatus cancel repeatable run-out (RRO) errors in positioning on a recording medium using a RRO cancellation control voltage. The RRO cancellation includes (a) estimating a rotation period of the recording medium, (b) determining an update interval for the RRO cancellation control voltage based on the estimated rotation period and a desired number of updates to be performed per rotation, (c) updating a value of the RRO cancellation control voltage if a time period passed from a last update is greater than the update interval, and (d) applying the updated RRO cancellation voltage to control the positioning. A phase and a magnitude of the RRO cancellation control voltage may be determined for a RRO frequency range.
1. A method for canceling repeatable run-out (RRO) errors in positioning on a recording medium using a RRO cancellation control voltage, said method comprising:
estimating a rotation period of the recording medium;
determining an update interval for the RRO cancellation control voltage based on the estimated rotation period and a desired number of updates to be performed per rotation;
updating a value of the RRO cancellation control voltage if a time period passed from a last update is greater than the update interval; and
applying the updated RRO cancellation voltage to control the positioning.
2. The method of claim 1 , further comprising:
determining a phase and a magnitude of the RRO cancellation control voltage for a RRO frequency range.
3. The method of claim 2 , further comprising:
generating a sinusoidal function having the phase and the magnitude of the RRO cancellation control voltage.
4. The method of claim 3 , further comprising:
storing information of the sinusoidal function representing the RRO cancellation control voltage.
5. The method of claim 3 , further comprising:
calculating the sinusoidal function using a difference equation.
6. The method of claim 2 , wherein said determining the RRO cancellation control voltage includes:
measuring a servo control voltage in a feedback control loop for a driving system of the recoding medium, the servo control voltage being measured for a RRO frequency range when the positioning is locked.
7. The method of claim 2 , wherein said determining the RRO cancellation control voltage includes:
measuring a tracking error in the positioning for a RRO frequency range when the positioning is locked.
8. The method of claim 1 , wherein said estimating the rotation period includes:
measuring a rotation period of a spindle motor adapted to drive the recording medium.
9. The method of claim 1 , wherein said estimating the rotation period includes:
determining a rotation period of a spindle motor based on a target speed of the spindle motor.
10. The method of claim 1 , further comprising:
recalculating the update interval for the RRO cancellation control voltage if the rotation period changes.
11. The method of claim 1 , wherein in said updating the time period is measured using a software timer independent of rotation of a spindle motor adapted to drive the recording medium.
12. The method of claim 1 , wherein in said updating the time period is measured using a counter independent of rotation of a spindle motor adapted to drive the recording medium.
13. The method of claim 1 , wherein the RRO cancellation control voltage is applied through a feed-forward control.
14. The method of claim 1 , wherein the recording medium includes:
a compact disc (CD); and
a digital versatile disc (DVD).
15. The method of claim 1 , wherein the recording medium is an optical recording medium.
16. The method of claim 1 , further comprising:
monitoring a residual RRO; and
increasing the number of update based on an amount of the residual RRO.
17. An apparatus for canceling repeatable run-out (RRO) errors in positioning on a recording medium using a RRO cancellation control voltage, said apparatus comprising:
means for estimating a rotation period of the recording medium;
means for determining an update interval for the RRO cancellation control voltage based on the estimated rotation period and a desired number of updates to be performed per rotation;
means for updating a value of the RRO cancellation control voltage if a time period passed from a last update is greater than the update interval; and
means for applying the updated RRO cancellation voltage to control the positioning.
18. The apparatus of claim 17 , further comprising:
means for determining a phase and a magnitude of the RRO cancellation control voltage for a RRO frequency range.
19. The apparatus of claim 18 , further comprising:
means for generating a sinusoidal function having the phase and the magnitude of the RRO cancellation control voltage.
20. The apparatus of claim 19 , further comprising:
means for storing information of the sinusoidal function representing the RRO cancellation control voltage.
21. The apparatus of claim 19 , further comprising:
means for calculating the sinusoidal function using a difference equation.
22. The apparatus of claim 18 , wherein said means for determining the RRO cancellation control voltage includes:
means for measuring a servo control voltage in a feedback control loop for a driving system of the recoding medium, the servo control voltage being measured for a RRO frequency range when the positioning is locked.
23. The apparatus of claim 18 , wherein said means for determining the RRO cancellation control voltage includes:
means for measuring a tracking error in the positioning for a RRO frequency range when the positioning is locked.
24. The apparatus of claim 17 , wherein said means for estimating the rotation period includes:
means for measuring a rotation period of a spindle motor adapted to drive the recording medium.
25. The apparatus of claim 17 , wherein said means for estimating the rotation period includes:
means for determining a rotation period of a spindle motor based on a target speed of the spindle motor.
26. The apparatus of claim 17 , further comprising:
means for recalculating the update interval for the RRO cancellation control voltage if the rotation period changes.
27. The apparatus of claim 17 , wherein said means for updating performs updates using a software timer independent of rotation of a spindle motor adapted to drive the recording medium.
28. The apparatus of claim 17 , wherein said means for updating performs updates using a counter independent of rotation of a spindle motor adapted to drive the recording medium.
29. The apparatus of claim 17 , wherein the RRO cancellation control voltage is applied through a feed-forward control.
30. The apparatus of claim 17 , wherein the recording medium includes:
a compact disc (CD); and
a digital versatile disc (DVD).
31. The apparatus of claim 17 , wherein the recording medium is an optical recording medium.
32. The apparatus of claim 17 , further comprising:
monitoring a residual RRO; and
increasing the number of update based on an amount of the residual RRO.
33. A system for canceling repeatable run-out (RRO) errors in positioning on a recording medium using a RRO cancellation control voltage, said system comprising:
a rotation period determiner adapted to receive a pulse signal from a disc driver for driving the recording medium; and
a RRO cancellation generator coupled to said rotation period determiner, said RRO cancellation generator outputting an updated cancellation control signal at an update interval such that a desired number of updates are performed per rotation in accordance with a clock signal independent of rotation of the spindle motor.
34. The system of claim 33 , further comprising:
a spindle speed controller coupled to said rotation speed detector and a spindle motor of the disc driver; and
a servo controller adapted to control tracking and positioning of a read/write unit of the disc driver.
35. The system of claim 33 , wherein said RRO cancellation generator includes:
a memory adapted to store information of a sinusoidal function representing the RRO cancellation control voltage.
36. The system of claim 35 , wherein the information is in form of a lookup table.
37. The system of claim 33 , said RRO cancellation generator includes:
a calculator adapted to calculate a sinusoidal function representing the RRO cancellation control voltage using a difference equation.
38. The system of claim 33 , wherein said rotation period determiner includes:
a rotation detector adapted to measure a rotation period of the spindle motor.
39. The system of claim 33 , wherein said rotation period determiner includes:
a rotation period calculator adapted to calculate a rotation period of a spindle motor based on a target speed of the spindle motor and servo control information.
40. The system of claim 33 , wherein said rotation period determiner includes:
a rotation period re-calculator adapted to recalculate the update interval for the RRO cancellation control voltage if the rotation period changes.
41. The system of claim 33 , wherein the clock signal is supplied by a software timer.
42. The system of claim 33 , wherein the clock signal is supplied by a hardware counter.
43. The system of claim 33 , wherein the recording medium includes:
a compact disc (CD); and
a digital versatile disc (DVD).
44. The system of claim 33 , wherein the recording medium is an optical recording medium.
45. The system of claim 33 , further comprising:
a monitor adapted to monitor a residual RRO; and
an update incrementor coupled to said monitor and said RRO cancellation generator, adapted to increase the number of update based on an amount of the residual RRO.
46. A program storage device readable by a machine, tangibly embodying a program of instructions executable by the machine to perform a method for canceling repeatable run-out (RRO) errors in positioning on a recording medium using a RRO cancellation control voltage, said method comprising:
estimating a rotation period of the recording medium;
determining an update interval for the RRO cancellation control voltage based on the estimated rotation period and a desired number of updates to be performed per rotation;
updating a value of the RRO cancellation control voltage if a time period passed from a last update is greater than the update interval; and
applying the updated RRO cancellation voltage to control the positioning.
47. The program storage device of claim 46 , wherein said method further comprises:
determining a phase and a magnitude of the RRO cancellation control voltage for a RRO frequency range.
48. The program storage device of claim 47 , wherein said method further comprises:
generating a sinusoidal function having the phase and the magnitude of the RRO cancellation control voltage.
49. The program storage device of claim 48 , wherein said method further comprises:
storing information of the sinusoidal function representing the RRO cancellation control voltage.
50. The program storage device of claim 48 , further wherein said method further comprises:
calculating the sinusoidal function using a difference equation.
51. The program storage device of claim 47 , wherein in said method, said determining the RRO cancellation control voltage includes:
measuring a servo control voltage in a feedback control loop for a driving program storage device of the recoding medium, the servo control voltage being measured for a RRO frequency range when the positioning is locked.
52. The program storage device of claim 47 , wherein in said method, said determining the RRO cancellation control voltage includes:
measuring a tracking error in the positioning for a RRO frequency range when the positioning is locked.
53. The program storage device of claim 46 , wherein in said method, said estimating the rotation period includes:
measuring a rotation period of a spindle motor adapted to drive the recording medium.
54. The program storage device of claim 46 , wherein in said method, said estimating the rotation period includes:
determining a rotation period of a spindle motor based on a target speed of the spindle motor.
55. The program storage device of claim 46 , wherein said method further comprises:
recalculating the update interval for the RRO cancellation control voltage if the rotation period changes.
56. The program storage device of claim 46 , wherein in said updating the time period is measured using a software timer independent of rotation of a spindle motor adapted to drive the recording medium.
57. The program storage device of claim 46 , wherein in said updating the time period is measured using a counter independent of rotation of a spindle motor adapted to drive the recording medium.
58. The program storage device of claim 46 , wherein in said method, the RRO cancellation control voltage is applied through a feed-forward control.
59. The program storage device of claim 46 , wherein the recording medium includes:
a compact disc (CD); and
a digital versatile disc (DVD).
60. The program storage device of claim 46 , wherein the recording medium is an optical recording medium.
61. The program storage device of claim 46 , wherein said method further comprises:
monitoring a residual RRO; and
increasing the number of update based on an amount of the residual RRO.