Method and apparatus for spindle motor control

• US 7,378,810 B1
• Filed: 01/06/2004
• Issued: 05/27/2008
• Est. Priority Date: 05/20/2003
• Status: Active Grant

• Current Assignee: Marvell Asia Pte Limited (Marvell Technology Group Limited)
• Original Assignee: Marvell International Limited (Marvell Technology Group Limited)
• Inventors: Sutardja, Pantas, Richgels, Jerry
• Primary Examiner(s): Leykin; Rita
• Application Number:
  US10/752,601
• Time in Patent Office: 1,603 Days
• Field of Search: 318/255, 318/254, 318/59, 318/268, 318/778, 318/779, 318/439, 318/560, 318/301, 318/445, 388/800, 388/808, 388/823, 388/825, 388/834
• US Class Current: 318/268
• CPC Class Codes: G11B 19/28 Speed controlling, regulating, or indicating G11B19/24 takes precedence
• CPC Class Codes: H02P 6/182 using back-emf in windings

Abstract

Information indicative of the placement of spindle motor components may be obtained and used to provide a correction to one or more BEMF-derived attributes used to control the spindle speed. In some implementations, first and second signals indicative of BEMF of different stator windings may be used to determine a speed-related characteristic. The speed related characteristic may be used to determine an error amount, which may be used to determine a correction factor to control the speed of the spindle motor.

Claims

1. A method of spindle motor control, comprising:

(A) receiving a first signal indicative of a back electromotive force (BEMF) induced in a first stator winding;

(B) receiving a second signal indicative of a BEMF induced in a second different stator winding;

(C) determining a speed-related characteristic associated with motor asymmetry based on at least one of the first signal and the second signal;

(D) determining an error amount based on the speed-related characteristic;

(E) determining a correction factor for the speed-related characteristic based on the error amount; and

(F) controlling a speed of the spindle motor using the correction factor.

2. The method of claim 1, wherein the speed-related characteristic is a measured time difference between a characteristic of the first signal and a corresponding characteristic of the second signal.

3. The method of claim 2, wherein the characteristic of the first signal is a zero crossing of the first signal corresponding to a rotational state of a rotor, and wherein the corresponding characteristic of the second signal is a zero crossing of the second signal corresponding to the rotational state of the rotor.

4. The method of claim 2, wherein determining the error amount based on the speed-related characteristic comprises determining a difference between the measured time difference and a reference time difference.

5. The method of claim 4, wherein the reference time difference corresponds to a desired rotational speed of the spindle motor.

6. The method of claim 1, further comprising controlling the speed of the spindle motor using the speed-related characteristic.

7. The method of claim 1, wherein determining a correction factor comprises determining the correction factor based on only the error amount.

8. The method of claim 1, wherein determining a correction factor comprises repeating (A) through (C) one or more times to determine one or more additional error amounts and determining the correction factor based on at least one of the error amount and the one or more additional error amounts.

9. The method of claim 8, wherein determining the correction factor based on at least one of the error amount and one or more additional error amounts comprises determining the correction factor based on an average of the error amount and the one or more additional error amounts.

10. The method of claim 8, further comprising filtering the error amount and the one or more additional error amounts to produce filtered error amount data, and wherein determining the correction factor based on at least one of the error amount and one or more additional amounts comprises determining the correction factor based on the filtered error amount data.

11. The method of claim 1, wherein the speed-related characteristic based on at least one of the first signal and the second signal is a phase difference between a characteristic of the first signal and a characteristic of a reference clock.

12. The method of claim 1, further comprising:

controlling a spindle motor speed using the correction factor;

repeating (A) to (D); and

determining a second correction factor for the speed-related characteristic.

13. The method of claim 1, further comprising determining a gain of a spindle motor control feedback system, and wherein the correction factor is further based on the gain.

14. The method of claim 1, further comprising controlling the spindle motor speed based on timing marks from servo sectors.

15. The method of claim 14, wherein controlling the spindle motor speed based on timing marks from servo sectors comprises:

receiving a first signal from a first servo sector;

receiving a second signal from a second servo sector;

determining a speed-related characteristic based on at least one of the first signal and the second signal;

determining an error amount based on the speed-related characteristic; and

determining a correction factor for the speed-related characteristic based on the error amount.

16. A computer program operable to cause one or more machines to perform operations comprising:

(A) receiving a first signal indicative of a back electromotive force (BEMF) induced in a first stator winding;

(B) receiving a second signal indicative of a BEMF induced in a second different stator winding;

(C) determining a speed-related characteristic associated with motor asymmetry based on at least one of the first signal and the second signal;

(D) determining an error amount based on the speed-related characteristic;

(E) determining a correction factor for the speed-related characteristic based on the error amount; and

(F) controlling a speed of the spindle motor using the correction factor.

17. The program of claim 16, wherein the speed-related characteristic is a measured time difference between a characteristic of the first signal and a corresponding characteristic of the second signal.

18. The program of claim 17, wherein the characteristic of the first signal is a zero crossing of the first signal corresponding to a rotational state of a rotor, and wherein the corresponding characteristic of the second signal is a zero crossing of the second signal corresponding to the rotational state of the rotor.

19. The program of claim 17, wherein determining the error amount based on the speed-related characteristic comprises determining a difference between the measured time difference and a reference time difference.

20. The program of claim 19, wherein the reference time difference corresponds to a desired rotational speed of the spindle motor.

21. The pro of claim 16, further comprising controlling the speed of the spindle motor using the speed-related characteristic.

22. The program of claim 16, wherein determining a correction factor comprises determining the correction factor based on only the error amount.

23. The program of claim 16, wherein determining a correction factor comprises repeating (A) through (C) one or more times to determine one or more additional error amounts and determining the correction factor based on at least one of the error amount and the one or more additional error amounts.

24. The program of claim 23, wherein determining the correction factor based on at least one of the error amount and one or more additional error amounts comprises determining the correction factor based on an average of the error amount and the one or more additional error amounts.

25. The program of claim 23, further comprising filtering the error amount and the one or more additional error amounts to produce filtered error amount data, and wherein determining the correction factor based on at least one of the error amount and one or more additional amounts comprises determining the correction factor based on the filtered error amount data.

26. The program of claim 16, wherein the speed-related characteristic based on at least one of the first signal and the second signal is a phase difference between a characteristic of the first signal and a characteristic of a reference clock.

27. The program of claim 16, further comprising:

controlling a spindle motor speed using the correction factor;

repeating (A) to (D); and

determining a second correction factor for the speed-related characteristic.

28. The program of claim 16, further comprising determining a gain of a spindle motor control feedback system, and wherein the correction factor is further based on the gain.

29. The program of claim 16, further comprising controlling the spindle motor speed based on timing marks from servo sectors.

30. The program of claim 29, wherein controlling the spindle motor speed based on timing marks from servo sectors comprises:

receiving a first signal from a first servo sector;

receiving a second signal from a second servo sector;

determining a speed-related characteristic based on at least one of the first signal and the second signal;

determining an error amount based on the speed-related characteristic; and

determining a correction factor for the speed-related characteristic based on the error amount.

31. A spindle motor controller, comprising:

one or more inputs configured to receive signals from a spindle motor, the signals including a first signal indicative of a back electromotive force (BEMF) induced in a first stator winding and a second signal indicative of a BEMF induced in a second different stator winding; and

a processor configured to;

determine a speed-related characteristic associated with motor asymmetry based on at least one of the first signal and the second signal;

determine an error amount based on the speed-related characteristic;

determine a correction factor for the speed-related characteristic based on the error amount; and

generate an output signal using the correction factor, the output signal to control the speed of the spindle motor.

32. The controller of claim 31, wherein the processor includes at least one of a signal processor and a data processor.

33. The controller of claim 31, wherein the speed-related characteristic is a measured time difference between a characteristic of the first signal and a corresponding characteristic of the second signal.

34. The controller of claim 33, further including a memory, the memory configured to store a reference time difference, and wherein determining the error amount based on the speed-related characteristic comprises determining a difference between the measured time difference and the reference time difference.

35. A spindle motor controller, comprising:

input means for receiving signals from a spindle motor, the signals including a first signal indicative of a back electromotive force (BEMF) induced in a first stator winding and a second signal indicative of a BEMF induced in a second different stator winding;

means for determining a speed-related characteristic associated with motor asymmetry based on at least one of the first signal and the second signal;

means for determining an error amount based on the speed-related characteristic;

means for determining a correction factor for the speed-related characteristic based on the error amount; and

means for generating an output signal using the correction factor, the output signal for controlling the speed of the spindle motor.

36. The controller of claim 35, wherein the means for determining a speed-related characteristic based on at least one of the first signal and the second signal, means for determining an error amount based on the speed-related characteristic, means for determining a correction factor for the speed-related characteristic based on the error amount;

and means for generating an output signal using the correction factor include at least one of a signal processing means and a data processing means.

37. The controller of claim 35, wherein the speed-related characteristic is a measured time difference between a characteristic of the first signal and a corresponding characteristic of the second signal.

38. The controller of claim 37, further including a means for storing data, the data including a reference time difference, and wherein determining the error amount based on the speed-related characteristic comprises determining a difference between the measured time difference and the reference time difference.

39. A disc drive, comprising:

a disc having a storage surface;

a spindle motor in communication with the disc; and

a spindle motor controller to control the spindle motor to rotate the disc, the spindle motor controller including;

one or more inputs configured to receive signals from a spindle motor, the signals including a first signal indicative of a back electromotive force (BEMF) induced in a first stator winding and a second signal indicative of a BEMF induced in a second stator winding; and

a processor to determine a speed-related characteristic associated with motor asymmetry based on at least one of the first signal and the second signal, the processor to further determine an error amount based on the speed-related characteristic, the processor further to determine a correction factor for the speed-related characteristic based on the error amount.

40. The disc drive of claim 39, wherein the processor includes at least one of a signal processor and a data processor.

41. The disc drive of claim 39, wherein the speed-related characteristic is a measured time difference between a characteristic of the first signal and a corresponding characteristic of the second signal.

42. The disc drive of claim 39, further including a head assembly, the head assembly comprising:

a head;

an actuator arm to position the head with respect to the storage surface; and

an actuator drive to move the actuator arm.

43. A disc drive, comprising:

disc means for storing data, the disc means having a storage surface;

means for rotating the disc means in communication with the disc means; and

means for controlling the means for rotating, the means for controlling including;

input means for receiving signals from a spindle motor, the signals including a first signal indicative of a back electromotive force (BEMF) induced in a first stator winding and a second signal indicative of a BEMF induced in a second different stator winding;

means for determining a speed-related characteristic associated with motor asymmetry based on at least one of the first signal and the second signal;

means for determining an error amount based on the speed-related characteristic;

means for determining a correction factor for the speed-related characteristic based on the error amount; and

means for generating an output signal using the correction factor, the output signal for controlling the speed of the spindle motor.

44. The disc drive of claim 43, wherein the means for determining a speed-related characteristic based on at least one of the first signal and the second signal, means for determining an error amount based on the speed-related characteristic, means for determining a correction factor for the speed-related characteristic based on the error amount;

and means for generating an output signal using the correction factor include at least one of a signal processing means and a data processing means.

45. The disc drive of claim 43, wherein the speed-related characteristic is a measured time difference between a characteristic of the first signal and a corresponding characteristic of the second signal.

46. The disc drive of claim 43, further including a head assembly, the head assembly comprising:

head means for at least one of writing data to the disc means and reading data from the disc means;

means for positioning the head with respect to the storage surface; and

means for moving the head with respect to the storage surface.

47. A method of spindle motor control, comprising

receiving a first signal indicative of a back electromotive force (BEMF) induced in a first stator winding;

receiving a second signal indicative of a back electromotive force (BEMF) induced in a second stator winding;

obtaining information related to the placement of one or more motor components; and

controlling a speed of the spindle motor using at least one of the first signal and the second signal and the placement information, wherein controlling the speed includes correcting for asymmetry.