Detection of disk surface irregularities in data storage devices

• US 8,958,167 B1
• Filed: 02/12/2014
• Issued: 02/17/2015
• Est. Priority Date: 12/23/2013
• Status: Active Grant

• Current Assignee: JP Morgan Chase Bank, N.A. (JP Morgan Chase & Co)
• Original Assignee: Western Digital Technologies Incorporated (Western Digital Corporation)
• Inventors: Choeiprathum, Wiriya, Suvichakorn, Aimamorn
• Primary Examiner(s): Wong, K.
• Application Number:
  US14/179,355
• Time in Patent Office: 370 Days
• Field of Search: None
• US Class Current: 360/46
• CPC Class Codes: G11B 19/048 Testing of disk drives, e.g. to detect defects or prevent sudden failure

Abstract

Detecting surface irregularities on a disk of a data storage device (DSD) includes reading data from a first side of the disk using a first head of the DSD. A first set of variable gain amplifier (VGA) values is generated which is related to the reading of data from the first side using the first head. Data is read from a second side of the disk using a second head of the DSD and a second set of VGA values is generated which is related to the reading of data from the second side using the second head. A profile for the disk is determined using the first set of VGA values and the second set of VGA values. The profile is compared to at least one threshold to detect surface irregularities on the disk.

Claims

1. A data storage device (DSD) comprising:

a disk including a first side for storing data and a second side for storing data;

a first head for reading data from the first side;

a second head for reading data from the second side; and

circuitry configured to;

control the first head to read data from the first side;

generate a first set of variable gain amplifier (VGA) values related to the reading of data from the first side using the first head;

control the second head to read data from the second side;

generate a second set of VGA values related to the reading of data from the second side using the second head;

determine a profile for the disk using the first set of VGA values and the second set of VGA values;

set at least one threshold based on the profile; and

compare the profile to the at least one threshold to detect surface irregularities on the disk.

2. The DSD of claim 1, wherein the circuitry is further configured to:

exclude an outermost portion of the profile; and

set the at least one threshold as a multiple of an average of values from a remaining portion of the profile.

3. The DSD of claim 1, wherein the at least one threshold includes an upper threshold and a lower threshold.

4. The DSD of claim 1, wherein the circuitry is further configured to:

generate the first set of VGA values by averaging VGA values for groups of contiguous tracks on the first side; and

generate the second set of VGA values by averaging VGA values for groups of contiguous tracks on the second side.

5. The DSD of claim 1, wherein the circuitry is further configured to determine the profile by filtering the first set of VGA values and filtering the second set of VGA values.

6. The DSD of claim 5, wherein the circuitry is further configured to determine the profile by multiplying the filtered first set of VGA values with the filtered second set of VGA values.

7. The DSD of claim 1, wherein the circuitry is further configured to:

determine a distribution for the first set of VGA values and the second set of VGA values, wherein the first set of VGA values and the second set of VGA values are correlated in the distribution by a radial location on the disk; and

determine the profile by applying a differential Gaussian filter to a norm of the distribution.

8. The DSD of claim 1, wherein the circuitry is further configured to determine the profile by multiplying the first set of VGA values with the second set of VGA values.

9. The DSD of claim 1, wherein the circuitry is further configured to determine the profile by taking a difference between the first set of VGA values and the second set of VGA values.

10. The DSD of claim 1, wherein the circuitry is further configured to detect surface irregularities on the disk if the profile is outside of the at least one threshold or if more than a predetermined number of values from the profile are outside of the at least one threshold.

11. The DSD of claim 1, wherein the generated first and second sets of VGA values include servo VGA (SVGA) values related to the reading of data from servo wedges on the disk.

12. The DSD of claim 1, wherein the circuitry is further configured to filter the first set of VGA values and the second set of VGA values using a differential Gaussian filter.

13. A method for detecting surface irregularities on a disk of a data storage device (DSD), the method comprising:

reading data from a first side of the disk using a first head of the DSD;

generating a first set of variable gain amplifier (VGA) values related to the reading of data from the first side using the first head;

reading data from a second side of the disk using a second head of the DSD;

generating a second set of VGA values related to the reading of data from the second side using the second head;

determining a profile for the disk using the first set of VGA values and the second set of VGA values;

setting at least one threshold based on the profile; and

comparing the profile to the at least one threshold to detect surface irregularities on the disk.

14. The method of claim 13, further comprising:

excluding an outermost portion of the profile; and

setting the at least one threshold as a multiple of an average of values from a remaining portion of the profile.

15. The method of claim 13, wherein the at least one threshold includes an upper threshold and a lower threshold.

16. The method of claim 13, further comprising:

generating the first set of VGA values by averaging VGA values for groups of contiguous tracks on the first side; and

generating the second set of VGA values by averaging VGA values for groups of contiguous tracks on the second side.

17. The method of claim 13, further comprising determining the profile by filtering the first set of VGA values and filtering the second set of VGA values.

18. The method of claim 17, further comprising determining the profile by multiplying the filtered first set of VGA values with the filtered second set of VGA values.

19. The method of claim 13, further comprising:

determining a distribution for the first set of VGA values and the second set of VGA values, wherein the first set of VGA values and the second set of VGA values are correlated in the distribution by a radial location on the disk; and

determining the profile by applying a differential Gaussian filter to a norm of the distribution.

20. The method of claim 13, further comprising determining the profile by multiplying the first set of VGA values with the second set of VGA values.

21. The method of claim 13, further comprising determining the profile by taking a difference between the first set of VGA values and the second set of VGA values.

22. The method of claim 13, further comprising detecting surface irregularities on the disk if the profile is outside of the at least one threshold or if more than a predetermined number of values from the profile are outside of the at least one threshold.

23. The method of claim 13, wherein the generated first and second sets of VGA values include servo VGA (SVGA) values related to the reading of data from servo wedges on the disk.

24. The method of claim 13, further comprising filtering the first set of VGA values and the second set of VGA values using a differential Gaussian filter.