Mobile hard disk drive free fall detection and protection

• US 7,369,345 B1
• Filed: 12/02/2005
• Issued: 05/06/2008
• Est. Priority Date: 12/03/2004
• Status: Active Grant

• Current Assignee: Maxtor Corporation (Seagate Technology Holdings Plc), Seagate Technology LLC (Seagate Technology Holdings Plc)
• Original Assignee: Maxtor Corporation (Seagate Technology Holdings Plc)
• Inventors: Chew, Xiaokun, Northrup, Oliver, Glassburn, Tim, Heimbaugh, Mark, Scura, John E., Schreck, Erhard, Guo, Wei, Li, Yunfeng, Guo, Lin, Flynn, William
• Primary Examiner(s): Dinh; Tan
• Assistant Examiner(s): HABERMEHL, JAMES LEE
• Application Number:
  US11/292,831
• Time in Patent Office: 886 Days
• Field of Search: None
• US Class Current: 360/75
• CPC Class Codes: G11B 5/5582 system adaptation for working during or after external perturbation, e.g. in the presence of a mechanical oscillation caused by a shock

Abstract

A system provided for protecting a disk drive from impact damages. More specifically, a disk drive is provided that includes an accelerometer interconnected to a printed circuit board that detects free fall of the disk drive. In addition, the velocity of spinning disks of the disk drive is also monitored to assess changes in velocity thereof that may indicate the presence of a tumbling condition. Furthermore, the change in acceleration measured by the accelerometer is monitored to prevent false indications of free fall due to common vibrations. Thus an enhanced system is provided that protects disk drives from the effect of free falls under a wide variety of conditions and allowing for drops from shorter distances to be identified.

Claims

1. A method of preventing damage to a disk drive, the disk drive having at least one rotating disk and an actuator arm movable relative to the surface of the rotating disk to position a read and/or write element at select positions over the surface of the disk, the method comprising:

a. sensing the acceleration of the disk drive over time to determine free fall event;

b. simultaneously sensing the change in spin rate of the rotating disk over time to determine free fall event; and

c. initiating procedures to secure the actuator arm if free fall event is determined.

2. The method of claim 1, wherein sensing the acceleration of a disk drive over time comprises taking multiple samples of the acceleration over time.

3. The method of claim 1, further comprising:

a. comparing the acceleration of the disk drive to a first threshold value;

b. calculating the change of acceleration and comparing the change of acceleration to a second threshold value; and

c. determining free fall condition when the acceleration is below said first threshold value over a first predetermined period of time and the change of acceleration is below said second threshold value over a second predetermined period of time.

4. The method of claim 1, wherein initiating procedures to secure the actuator arm comprises sending a signal to the voice coil motor to move the actuator arm.

5. The method of claim 4, wherein said signal is sent to said voice coil motor if one or both of the following occurs:

the acceleration surpasses said first threshold value for said first predetermined period of time and the change of acceleration surpasses said second threshold value for a second predetermined period of time.

6. The method of claim 1, further comprising:

a. sensing tumble of the disk drive by sensing the change in spin rate of the rotating disk over time;

b. comparing the change in spin rate to a third threshold value; and

c. initiating procedures to secure the actuator arm if the change in spin rate exceeds a third threshold value for a third predetermined period of time.

7. The method of claim 6, wherein said signal is sent to said voice coil motor if at least one of the following occurs:

the acceleration surpasses said first threshold value for said first predetermined period of time, the change of acceleration surpasses said second threshold value for a second predetermined period of time, and the tumble detector surpasses the third threshold value for the third period of time.

8. The method of claim 1, further comprising moving the actuator arm to position the read and/or write element over a data free zone of the disk if at least one of the following occurs:

the acceleration surpasses said first threshold value for said first predetermined period of time, the change of acceleration surpasses said second threshold value for a second predetermined period of time, and the tumble detector surpasses the third threshold value for the third period of time.

9. The method of claim 1, further comprising loading the actuator arm on a support structure removed from the surface of the disk if at least one of the following occurs:

the acceleration surpasses said first threshold value for said first predetermined period of time, the change of acceleration surpasses said second threshold value for a second predetermined period of time, and the tumble detector surpasses the third threshold value for the third period of time.

10. The method of claim 9, further comprising detecting if the acceleration surpasses said first threshold value for said first predetermined period of time and the change of acceleration surpasses said second threshold value for a second predetermined period of time and loading the actuator arm on a support structure removed from the surface of the disk in less time than it take for the disk drive to fall four inches.

11. The method of claim 3, wherein the first and second threshold values are changeable by the end user to vary the sensitivity of the free fall detection system.

12. The method of claim 3, further comprising varying one or both of the first and second time period over which the acceleration and change of acceleration are assessed.

13. The method of claim 3, further comprising varying one or both of the time period over which the acceleration and/or the change of acceleration is assessed.

14. The method of claim 1, wherein sensing the acceleration of a disk drive comprises using an accelerometer.

15. The method of claim 14, wherein the accelerometer is a three-axis accelerometer attached inside the housing of disk drive.

16. The method of claim 6, wherein at least one of the first, second and third threshold values are changeable.

17. The method of claim 6, wherein at least one of the predetermined time periods associated with said first, second and third threshold values for initiating procedures to secure the actuator arm is changeable.

18. The method of claim 6, wherein sensing the change in spin rate comprises comparing the actual spin rate against a clock.

19. The method of claim 18, wherein sensing the change in spin rate comprises assessing an average spin rate based upon back electromotive force induced in the stator motor.

20. A disk drive comprising:

a. a housing;

b. at least one rotatable storage disk mounted within the housing, said disk having an inner and outer circumference and a data zone disposed between the inner and outer circumference;

c. an actuator arm movable relative to the disk to position a read and/or write element radially across the disk;

d. a sensor mounted within the housing to sense if the disk drive is falling from a first elevation to a second elevation by monitoring acceleration of the disk drive over time;

e. fall detection means for assessing the acceleration and change of acceleration, for determining if the acceleration is below a first threshold over a first period of time and change of acceleration is below a second threshold over a second period of time, and for outputting a first signal if the acceleration is below said first threshold over said first period of time and change of acceleration is below said second threshold over said second period of time; and

f. control means for causing movement of the actuator arm in the event that said first signal is generated.

21. The disk drive of claim 20, further comprising tumble detection means for sensing the spin rate of the rotating disk over time and determining if the spin rate exceeds a third threshold value over time, and for outputting a second signal if the spin rate exceeds the third threshold value over a third predetermined period of time.

22. The disk drive of claim 21, wherein said control means further comprises means for causing movement of the actuator arm in the event that said second signal is generated.

23. The disk drive of claim 20, wherein the sensor is mounted on or inside the housing.

24. The disk drive of claim 20, wherein the first and second time periods are of a different duration.

25. The disk drive of claim 20, wherein the sensor is a three-axis accelerometer.

26. The disk drive of claim 20, further comprising adjustment means for changing the duration of one or both of the first and second predetermined time periods.

27. The disk drive of claim 20, further comprising a hub on which the at least one rotatable disk is mounted, at least one permanent magnet associated with said hub, a stator comprising a plurality of electromagnets mounted within the housing of the disk drive, and a feed back loop operatively associated with the stator, said feed back loop monitoring variations in the spin rate of the at least one rotating disk based upon back electromotive force induced in the stator by said at least one permanent magnet.

28. The disk drive of claim 20 further comprising a servo controller for monitoring the position of the read and/or write element relative to the surface of the disk and for monitoring variations in the spin rate of the at least one rotating disk.

29. The disk drive of claim 20, wherein said control means further comprises means for causing movement of the actuator arm in the event that said first or second signal is generated.

30. The disk drive of claim 20, wherein said means for causing movement of the actuator arm in the event that said first signal is generated further causes the read and/or write element to be moved to a position off of the data zone.

31. The disk drive of claim 30 wherein the position of the read and/or write element is off of the disk.

32. The disk drive of claim 26, wherein said adjustment means permits changing the duration of the third predetermined time period.

33. The disk drive of claim 21, wherein said control means further comprises means for causing movement of the actuator arm in the event that said second signal is generated.

34. A method for detecting a falling disk drive, comprising:

a. sensing acceleration of the disk drive using an accelerometer;

b. calculating the change in acceleration over time;

c. comparing the acceleration to a first threshold value for over a first series of predetermined time periods;

d. comparing the change in acceleration over time to a second threshold value over a second series of predetermined time periods;

e. monitoring the spin rate of the disks in the disk drive;

f. comparing the spin rate to a clock value;

g. determining if the spin rate values from the expected value by a third threshold value over a third series of predetermined time periods;

h. generating a signal if any of the first, second or third threshold values are exceeded over the first, second or third time periods, respectively.

35. The method of claim 34, wherein at least one of the first, second and third threshold values are variable.

36. The method of claim 34, wherein at least one of the first, second and third predetermined time periods are variable.

37. The method of claim 34, wherein the disk drive comprises an actuator arm that moves relative to the surface of the disk and the actuator arm comprises a read and/or write element for reading data from and/or writing data to the disk, further comprising moving the read and/or write element to a new position following the step of generating a signal if any of the first, second or third threshold values are exceeded over the first, second or third time periods, respectively.

38. The method of claim 37, wherein the new position comprises a position in which the read and/or write element is loaded on a ramp off of the disk surface.

39. The method of claim 37, wherein the new position comprises a position in which the read and/or write element is positioned over a safe zone on the disk.

40. The method of claim 37, further comprising securing the actuator arm.

41. A method for detecting a falling disk drive, comprising:

a. sensing acceleration of the disk drive using an accelerometer;

b. calculating the change in acceleration over time;

c. comparing the acceleration to a first threshold value for over a first series of predetermined time periods;

d. monitoring the spin rate of the disks in the disk drive;

e. comparing the spin rate to a clock value;

f. determining if the spin rate varies from the expected value by a second threshold value over a second series of predetermined time periods; and

g. generating a signal if either of the first or second threshold values are exceeded over the first or second time periods, respectively.

42. The method of claim 41, wherein monitoring the spin rate of the disks comprises not monitoring control current of the spin motor.

43. The method of claim 41, wherein sensing acceleration over time comprises taking multiple samples of the acceleration over time.

44. The method of claim 41, further comprising positioning the actuator arm in a safe position following generation of a signal.

45. The method of claim 44, wherein the safe position is a loaded position with the head off of the disk.

46. The method of claim 44, wherein the safe position is a position with the head over a designated zone of the disk.

47. The method of claim 41, wherein one of the first and second threshold values are changeable.

48. The method of claim 41, wherein both the first and second threshold values are changeable.

49. The method of claim 41, wherein one of the first and second predetermined time periods are changeable.

50. The method of claim 41, wherein both the first and second predetermined time periods are changeable.

51. The method of claim 41, wherein sensing the change in spin rate comprises assessing an average spin rate based upon back electromotive force induced in the stator motor.

52. A disk drive comprising:

a. a housing;

b. at least one rotatable storage disk mounted within the housing, said disk having an inner and outer circumference and a data zone disposed between the inner and outer circumference;

c. an actuator arm movable relative to the disk to position a read and/or write element radially across the disk;

d. a sensor mounted within the housing to sense if the disk drive is falling from a first elevation to a second elevation by monitoring acceleration of the disk drive over time;

e. fall detection means for assessing the acceleration and change of acceleration, for determining if the acceleration is below a first threshold over a first period of time and change of acceleration is below a second threshold over a second period of time, and for outputting a first signal if the acceleration is below said first threshold over said first period of time and change of acceleration is below said second threshold over said second period of time;

f. tumble detection means for sensing the spin rate of the rotating disk over time and determining if the spin rate exceeds a third threshold value over time, and for outputting a second signal if the spin rate exceeds the third threshold value over a third predetermined period of time; and

g. control means for causing movement of the actuator arm in the event that either or both of said first and second signals are generated.

53. The disk drive of claim 52, wherein said first and second time periods are of a different duration.

54. The disk drive of claim 53, wherein said sensor is a three-axis accelerometer.

55. The disk drive of claim 52, wherein one or more of said first, second and third threshold values are changeable.

56. The disk drive of claim 52, wherein one or more of said first, second and third predetermined periods of time are changeable.