Method and system to monitor magnetic head loading and unloading stability for a data storage system

• US 9,401,165 B1
• Filed: 06/13/2014
• Issued: 07/26/2016
• Est. Priority Date: 05/05/2014
• 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: Tian, Jifang, Chahwan, Alain
• Primary Examiner(s): Holder, Regina N
• Application Number:
  US14/303,955
• Time in Patent Office: 774 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: G11B 5/54 with provision for moving the head into or out of its operative position or across tracks
• 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 method and system to monitor stability of magnetic head loading and unloading beside media for a data storage system is described. A shock sensor is utilized to detect shock during preloading of a magnetic head beside recording media, during loading of a magnetic head beside recording media, during pre-unloading of a magnetic head from the recording media, and/or during unloading of a magnetic head from the recording media. In an aspect, a desired pitch static attitude (PSA) and roll static attitude (RSA) of a slider is determined. In an aspect, the stability of a magnetic head is assessed and screened while on the fly and during head gimbal assembly (HGA) design and testing to improve overall data storage device reliability.

Claims

1. An apparatus for monitoring at least one of loading stability and unloading stability of a magnetic head beside recording media, for a data storage system, the apparatus comprising:

a magnetic head;

a shock sensor to detect shock during at least one of i.) preloading of the magnetic head beside the recording media, ii.) loading of the magnetic head beside the recording media, iii.) pre-unloading of the magnetic head from the recording media, and iv.) unloading of the magnetic head from the recording media; and

a controller to monitor a shock detection signal from the shock sensor, and to determine whether the shock detection signal exceeds a predetermined threshold for pitch static attitude (PSA) and roll static attitude (RSA) of a slider joined to the magnetic head.

2. The apparatus as in claim 1, wherein the shock sensor comprises a shock sensing circuit including an amplifier and a filter, wherein the sensitivity of the shock sensing circuit is configurable by at least one of:

i.) adjusting a bandwidth of the filter, and ii.) adjusting a gain of the amplifier.

3. The apparatus as in claim 1, further comprising a voice coil motor (VCM) that, when generates a predetermined current signature, triggers the controller to monitor the shock sensor shock detection signal.

4. The apparatus as in claim 1, wherein the controller monitors the stability of the magnetic head by at least one of:

i.) determining magnitude of the shock sensor signal, comparing the shock sensor signal magnitude with the predetermined shock threshold limit, and determining whether the shock sensor signal magnitude exceeds the predetermined shock threshold limit;

ii.) determining magnitude of the shock sensor signal using a recursive root-mean square (RMS) value measured in the time domain, comparing the shock sensor signal RMS value with the predetermined shock threshold limit, and determining whether the shock sensor signal RMS value exceeds the predetermined shock threshold limit;

iii.) determining variance of the shock sensor signal, comparing the shock sensor signal variance with the predetermined shock threshold limit, and determining whether the shock sensor variance exceeds the predetermined shock threshold limit; and

iv.) determining spectrum of the shock sensor signal, comparing a fast Fourier transform (FFT) of the shock sensor signal with the predetermined shock threshold limit, and determining whether the FFT of the shock sensor signal exceeds the predetermined shock threshold limit.

5. The apparatus as in claim 1, wherein the controller:

i.) tracks a shock sensor signal that exceeds the predetermined shock threshold limit during a predetermined time period, ii.) tracks head loading or unloading cycles during the predetermined time period, and iii.) determines a percentage of shock sensor signals that exceed the predetermined shock threshold limit relative to head load or unload cycles.

6. A non-transitory machine-readable medium including executable instructions for monitoring a data storage system, the instructions comprising code for:

monitoring at least one of loading stability and unloading stability of a magnetic head beside recording media, by determining whether a signal from a shock sensor exceeds a predetermined pitch static attitude (PSA) and roll static attitude (RSA) threshold of a slider joined to the magnetic head, wherein the shock sensor detects shock during at least one of i.) preloading of the magnetic head beside the recording media, ii.) loading of the magnetic head beside the recording media, iii.) pre-unloading of the magnetic head from the recording media, and iv.) unloading of the magnetic head from the recording media.

7. The non-transitory machine-readable medium as in claim 6, further comprising utilizing a predetermined current signature from a voice coil motor (VCM) to trigger monitoring the shock sensor signal.

8. The non-transitory machine-readable medium as in claim 6, wherein monitoring the stability of the magnetic head comprises at least one of:

i.) determining magnitude of the shock sensor signal, comparing the shock sensor signal magnitude with a predetermined shock threshold limit, and determining whether the shock sensor signal magnitude exceeds the predetermined shock threshold limit;

ii.) determining magnitude of the shock sensor signal using a recursive root-mean square (RMS) value measured in the time domain, comparing the shock sensor signal RMS value with the predetermined shock threshold limit, and determining whether the shock sensor signal RMS value exceeds the predetermined shock threshold limit;

iii.) determining variance of the shock sensor signal, comparing the shock sensor signal variance with the predetermined shock threshold limit, and determining whether the shock sensor variance exceeds the predetermined shock threshold limit; and

iv.) determining spectrum of the shock sensor signal, comparing a fast Fourier transform (FFT) of the shock sensor signal with the predetermined shock threshold limit, and determining whether the FFT of the shock sensor signal exceeds the predetermined shock threshold limit.

9. The non-transitory machine-readable medium as in claim 6, further comprising:

i.) tracking shock sensor signals that exceed a predetermined shock threshold limit during a predetermined time period, ii.) tracking head loading or unloading cycles during the predetermined time period, and iii.) determining a percentage of shock sensor signals that exceed the predetermined shock threshold limit relative to head load or unload cycles.

10. The non-transitory machine-readable medium as in claim 6, wherein

monitoring the stability of the magnetic head is performed during a head gimbal assembly (HGA) loading or unloading quality back-end test, or during a HGA or head stack assembly (HSA) component test.

11. A method for a data storage system comprising:

monitoring at least one of loading stability and unloading stability of a magnetic head beside recording media, by determining whether a signal from a shock sensor exceeds a predetermined pitch static attitude (PSA) and roll static attitude (RSA) threshold of a slider joined to the magnetic head, wherein the shock sensor detects shock during at least one of i.) preloading of the magnetic head beside the recording media, ii.) loading of the magnetic head beside the recording media, iii.) pre-unloading of the magnetic head from the recording media, and iv.) unloading of the magnetic head from the recording media.

12. The method as in claim 11, further comprising utilizing a predetermined current signature from a voice coil motor (VCM) to trigger monitoring the shock sensor signal.

13. The method as in claim 11, wherein monitoring the stability of the magnetic head comprises at least one of:

i.) determining magnitude of the shock sensor signal, comparing the shock sensor signal magnitude with a predetermined shock threshold limit, and determining whether the shock sensor signal magnitude exceeds the predetermined shock threshold limit;

ii.) determining magnitude of the shock sensor signal using a recursive root-mean square (RMS) value measured in the time domain, comparing the shock sensor signal RMS value with the predetermined shock threshold limit, and determining whether the shock sensor signal RMS value exceeds the predetermined shock threshold limit;

iii.) determining variance of the shock sensor signal, comparing the shock sensor signal variance with the predetermined shock threshold limit, and determining whether the shock sensor variance exceeds the predetermined shock threshold limit; and

iv.) determining spectrum of the shock sensor signal, comparing a fast Fourier transform (FFT) of the shock sensor signal with the predetermined shock threshold limit, and determining whether the FFT of the shock sensor signal exceeds the predetermined shock threshold limit.

14. The method as in claim 11, further comprising utilizing a controller to determine whether the shock sensor signal exceeds a predetermined threshold limit.

15. The method as in claim 11, further comprising:

i.) tracking shock sensor signals that exceed a predetermined shock threshold limit during a predetermined time period, ii.) tracking head loading or unloading cycles during the predetermined time period, and iii.) determining a percentage of shock sensor signals that exceed the predetermined shock threshold limit relative to head load or unload cycles.

16. The method as in claim 11, further comprising:

i.) setting a bandwidth of the shock sensor signal, utilizing a low pass filter, and

ii.) setting a gain of the shock sensor signal to adjust the sensitivity of the shock sensor, utilizing an amplifier.

17. The method as in claim 11, wherein monitoring stability of the magnetic head further comprises at least one of:

a.) monitoring piezoelectric transducer (PZT) induced voltage on a head gimbal assembly (HGA) during at least one of;

i.) preloading of the magnetic head beside the recording media, ii.) loading of the magnetic head beside the recording media, iii.) pre-unloading of the magnetic head from the recording media, and iv.) unloading of the magnetic head from the recording media, and

b.) monitoring spindle speed during at least one of;

i.) preloading of the magnetic head beside the recording media, ii.) loading of the magnetic head beside the recording media, iii.) pre-unloading of the magnetic head from the recording media, and iv.) unloading of the magnetic head from the recording media.

18. The method as in claim 11, wherein monitoring the stability of the magnetic head is performed during a head gimbal assembly (HGA) loading or unloading quality back-end test, or during a HGA or head stack assembly (HSA) component test.