Management of tape drive quality using discrete fourier transform analysis

• US 8,958,170 B1
• Filed: 02/17/2014
• Issued: 02/17/2015
• Est. Priority Date: 02/17/2014
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Harper, David H. F.
• Primary Examiner(s): Neyzari, Ali
• Application Number:
  US14/182,003
• Time in Patent Office: 365 Days
• Field of Search: 360/77.04, 360/77.08, 360/55, 360/75, 360/51, 360/31, 360/60, 360/77.02, 360/77.12, 360/134, 360/77.15, 360/70, 360/77.14, 360/73.04, 360/53, 360/63, 360/291, 360/251
• US Class Current: 360/78.02
• CPC Class Codes: G11B 15/602 for track selection, acquisition or following

Abstract

Embodiments of the present disclosure relates to a method, system, and computer program product for determining an error contribution from a roller bearing in a tape drive. The method includes receiving, from a tape drive, a Position Error Signal (PES) data set. The method also includes determining a number of Discrete Fourier Transform (DFT) iterations based upon a frequency of interest and the number of samples. The method also includes performing, based upon the determined number of DFT iterations, a plurality of DFT iterations on the PES data set including the frequency of interest. Each DFT iteration is performed on a different number of samples from the PES data set. The method also includes identifying a plurality of amplitudes from the plurality of DFT iterations that corresponds to disturbance contributions from one of the rollers in the tape drive.

Claims

1. A method comprising:

receiving, from a tape drive, a Position Error Signal (PES) data set, that describes a positional variance of a head tape interface in relation to a tape and that has a number of samples;

determining a frequency of interest based on a size of one or more rollers in the tape drive and a velocity of the tape;

determining a number of Discrete Fourier Transform (DFT) iterations based upon the frequency of interest and the number of samples;

performing, based upon the determined number of DFT iterations, a plurality of DFT iterations on the PES data set including the frequency of interest, each DFT iteration performed on a different number of samples from the PES data set; and

identifying a plurality of amplitudes from the plurality of DFT iterations that corresponds to disturbance from one of the rollers in the tape drive.

2. The method of claim 1, further comprising:

determining the amplitude of interest from the plurality of amplitudes from the plurality of DFT iterations.

3. The method of claim 2, further comprising:

comparing the amplitude of interest to an amplitude threshold; and

accepting the tape drive in response to the amplitude of interest being within the amplitude threshold.

4. The method of claim 3, further comprising:

rejecting the tape drive in response to the amplitude of interest being outside the amplitude threshold.

5. The method of claim 2, wherein determining the amplitude of interest includes

determining a maximum amplitude value for the plurality of amplitudes.

6. The method of claim 1, wherein determining the frequency of interest includes

determining a harmonic of the frequency of interest.

7. The method of claim 1, wherein determining the frequency of interest includes:

receiving a frequency tolerance range; and

selecting one or more frequencies within the frequency tolerance range for the frequency of interest.

8. The method of claim 1, wherein the performing a plurality of DFT iterations on the PES data set includes:

initializing a window that has a window size corresponding to a number of samples from the PES data set;

performing an initial DFT iteration on the window of samples from the PES data set;

changing the window size by at least one sample;

performing a subsequent DFT iteration on the changed window; and

stopping the plurality of DFT iterations in response to a number of DFT iterations performed being at least equal to the determined number of DFT iterations.

9. The method of claim 8, wherein the changing the window size includes:

reducing the window from a higher time value to a lower time value.

10. The method of claim 9, further comprising:

reducing the window from a lower time value to a higher time value.

11. A tape drive testing system comprising:

a tape drive that is configured to read a position error signal (PES) from a storage tape that describes a positional variance of a head tape interface in relation to the storage tape; and

a position error signal (PES) analysis module that is configured to;

receive, from the tape drive, a PES data set that has a number of samples,

determine a frequency of interest based on a size of one or more rollers in the tape drive and a velocity of the storage tape,

determine a number of Discrete Fourier Transform (DFT) iterations based upon the frequency of interest and the number of samples,

perform, based upon the determined number of DFT iterations, a plurality of DFT iterations on the PES data set including the frequency of interest, each DFT iteration performed on a different number of samples from the PES data set, and

identify a plurality of amplitudes from the plurality of DFT iterations that corresponds to noise from one of the rollers in the tape drive.

12. The system of claim 11, wherein the PES analysis module is configured to:

determine the amplitude of interest from the plurality of amplitudes from the plurality of DFT iterations.

13. The system of claim 12, wherein the PES analysis module is configured to:

compare the amplitude of interest to an amplitude threshold;

accept the tape drive in response to the amplitude of interest being within the amplitude threshold;

reject the tape drive in response to the amplitude of interest being outside the amplitude threshold.

14. The system of claim 11, wherein the PES analysis module is configured to determine the frequency of interest by determining a harmonic of the frequency of interest.

15. The system of claim 11, wherein the PES analysis module is configured to determine the frequency of interest by:

receiving a frequency tolerance range; and

selecting one or more frequencies within the frequency tolerance range for the frequency of interest.

16. The system of claim 11, wherein the PES analysis module is configured to perform a plurality of DFT iterations on the PES data set by:

initializing a window that has a window size corresponding to a number of samples from the PES data set;

performing an initial DFT iteration on the window of samples from the PES data set;

changing the window size by at least one sample;

performing a subsequent DFT iteration on the changed window; and

stopping the plurality of DFT iterations in response to a number of DFT iterations performed being at least equal to the determined number of DFT iterations.

17. The system of claim 16, wherein the changing the window size includes:

reducing the window from a higher time value to a lower time value.

18. A computer program product for testing a tape drive, the computer program product comprising a computer readable storage medium having program instructions embodied therewith, wherein the computer readable storage medium is not a transitory signal per se, the program instructions readable by a computer to cause the computer to perform a method comprising:

receiving, from the tape drive, a Position Error Signal (PES) data set, that describes a positional variance of a head tape interface in relation to a tape and that has a number of samples;

determining a frequency of interest based on a size of one or more rollers in the tape drive and a velocity of the tape;

determining a number of Discrete Fourier Transform (DFT) iterations based upon the frequency of interest and the number of samples;

performing, based upon the determined number of DFT iterations, a plurality of DFT iterations on the PES data set including the frequency of interest, each DFT iteration performed on a different number of samples from the PES data set; and

identifying a plurality of amplitudes from the plurality of DFT iterations that corresponds to noise from one of the rollers in the tape drive.

19. The computer program product of claim 18, wherein the program instructions readable by the computer cause the computer to perform a method further comprising:

determining the amplitude of interest from the plurality of amplitudes from the plurality of DFT iterations.

20. The computer program product of claim 19, wherein the program instructions readable by the computer cause the computer to perform a method further comprising:

comparing the amplitude of interest to an amplitude threshold; and

accepting the tape drive in response to the amplitude of interest being within the amplitude threshold.