Relation of rotational vibration stimuli to performance of a hard disc drive

• US 6,665,633 B2
• Filed: 09/12/2001
• Issued: 12/16/2003
• Est. Priority Date: 12/29/2000
• Status: Expired due to Fees

• Current Assignee: Seagate Technology LLC (Seagate Technology Holdings Plc)
• Original Assignee: Seagate Technology LLC (Seagate Technology Holdings Plc)
• Inventors: Foster, Michael P., Almgren, Glen D., Pottebaum, Kenneth L., Fioravanti, Louis J.
• Primary Examiner(s): Huff, Marc S.
• Assistant Examiner(s): SUAREZ, FELIX E
• Application Number:
  US09/951,565
• Publication Number:
  US 20020123860A1
• Time in Patent Office: 825 Days
• Field of Search: 702/33, 702/38, 702/44, 702/54, 702/56, 702/57, 702/94, 702/113, 702/141, 702/182, 434/45, 600/300, 706/45, 356/606, 360/31, 360/69
• US Class Current: 702/182
• CPC Class Codes: G11B 20/10 Digital recording or reproducing
• CPC Class Codes: G11B 25/043 using rotating discs
• CPC Class Codes: G11B 33/08 Insulation or absorption of undesired vibrations or sounds
• 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
• CPC Class Codes: G11B 5/59627 Aligning for runout, eccentricity or offset compensation G11B5/5534, G11B5/59677, G11B5/59688 take precedence

Abstract

In relating rotational vibration stimuli of a mechanical mounting environment to the performance of a disc drive, a method and system are provided of which the steps are selecting a sample disc drive of a drive species and mounting the sample disc drive within the mechanical mounting environment; attaching an accelerometer to the sample disc drive for measuring rotational vibration; inducing a predetermined rotational vibration stimuli into the mechanical mounting; collecting vibration data with the accelerometer for use in determining the rotational vibration index for the mechanical mounting environment; providing a rotational vibration index for the drive species for comparison with the determined rotational vibration index; and comparing the rotational vibration index calculated for the mechanical mounting environment with the rotational vibration index of the drive species to relate the rotational vibration stimuli of the mechanical mounting environment to the performance of the sample disc drive.

Claims

1. A method for relating rotational vibration stimuli of a mechanical mounting environment for a disc drive to performance of the disc drive by steps comprising:

(a) mounting a sample disc drive selected from a drive species into the mechanical mounting environment;

(b) imparting a predetermined rotational vibration stimuli to the mechanical mounting environment;

(c) measuring a rotational vibration experienced by the sample disc drive mounted in the mechanical mounting environment responding to the predetermined rotational vibration stimuli of step (b);

(d) providing a predetermined rotational vibration index for the drive species;

(e) determining a rotational vibration index for the mechanical mounting environment with the sample disc drive mounted to the mechanical environment; and

(f) comparing the rotational vibration index for the mechanical mounting environment with the sample disc drive mounted to the mechanical mounting environment with the predetermined rotational vibration index for the drive species to relate the rotational vibration stimuli of the mechanical mounting environment to the performance of the sample disc drive.

2. The method of claim 1 in which the mechanical mounting environment of step (a) is a system chassis, which accommodates at least one disc drive, wherein the system chassis is selected from a group comprising a computer system, a server system and a mass storage system.

3. The method of claim 1 in which the mechanical mounting environment of step (a) is a test system chassis.

4. The method of claim 1 in which the disc drive operation of step (b) is an execution of a predetermined seek algorithm selected from a group of seek algorithms comprising an alternate full stroke seek algorithm and an x-n seek algorithm.

5. The method of claim 1 in which the measurement of the rotational vibration experienced by the disc drive of step (c) is achieved through the use of an accelerometer.

6. The method of claim 1 in which step (c) comprising the steps of:

(c1) attaching an accelerometer to the sample disc drive for use in measuring a frequency and an amplitude of rotational vibration experienced by the sample disc drive mounted in the mechanical mounting environment;

(c2) supplying a computer with a data acquisition card communicating with the accelerometer for gathering, filtering, recording and displaying the frequency and the amplitude of rotation vibration experienced by the sample disc drive mounted in the mechanical mounting environment;

(c3) calibrating the computer with the data acquisition card communicating with the accelerometer to ensure signal integrity; and

(c4) measuring a rotational vibration experienced by the disc drive responding to the predetermined rotational vibration stimuli of step (b).

7. The method of claim 1 in which the predetermined rotational vibration stimuli of step (b) is provided by a predetermined seek algorithm executed by the sample disc drive.

8. The method of claim 6 in which the sample disc drive includes a rotatable disc surface and an adjacent read/write head for writing data to and reading data from the rotatable disc surface and in which the predetermined rotational vibration stimuli of step (b) is provided by a predetermined seek algorithm executed by the sample disc drive and further wherein the measuring step (c4) comprises the steps of:

(a) gathering, filtering, recording and displaying a frequency and an amplitude of rotation vibration experienced by the sample disc drive mounted in the mechanical mounting environment responding to the predetermined rotational vibration stimuli using the calibrated computer with the data acquisition card communicating with the accelerometer; and

(b) writing a predetermined data to the rotatable disc surface while gathering, filtering, recording and displaying a level of data through put and a level of non-recoverable errors encountered by the sample disc drive while writing the predetermined data to the rotatable disc surface, for use in determining the rotational vibration index for the mechanical mounting environment.

9. The method of claim 1 in which the rotational vibration index for the drive species of step (d) is provided by steps comprising:

(d1) selecting a first of a plurality of disc drives with a basedeck supporting a spindle motor assembly having an axis of rotation from the drive species and mounting a pair of accelerometers on the selected disc drive to detect a rotational vibration in the axis of rotation of the spindle motor assembly;

(d2) securing the selected disc drive to a vibration test fixture calibrated to provide vibration stimuli of selectable frequencies and power spectral densities to the selected disc drive, the vibration test fixture for use in establishing vibrational tolerance limits for the drive species;

(d3) choosing and applying a first rotational vibration having a predetermined frequency and power spectral density to the basedeck while performing data transfer operations for use in determining the rotational vibration index for the drive species;

(d4) increasing the power spectral density of the rotational vibration to a point that substantially all reported errors are recoverable errors to establish an upper limit tolerance of the selected disc drive for the frequency of the rotational vibration chosen;

(d5) selecting a subsequent rotational vibration having a predetermined frequency and power spectral density different from the first selected rotational vibration and applying the subsequent selected rotational vibration to the basedeck while performing data transfer operations for use in determining the rotational vibration index for the drive species; and

(d6) repeating steps (d1) through (d5) across a predetermined frequency band for a predetermined number of disc drives selected from the drive species for use in determining an upper tolerance limit for power spectral density profile across the predetermined frequency band for use in determining a power spectral density profile specification across the predetermined frequency band for an individual disc drive of the drive species.

10. The method of claim 9 in which the rotational vibration index for the drive species of providing step (d) further comprises the steps of:

(d7) choosing a first of a plurality of the selected disc drives of the drive species for use in determining the rotational vibration index for the drive species;

(d8) attaching a pair of accelerometers to the first chosen selected disc drive to detect a rotational vibration in the axis of rotation of the spindle motor assembly and mounting the first chosen disc drive into a first of a plurality of chassis systems;

(d9) connecting the pair of accelerometers to a test system used to measure an energy level experienced by the first chosen selected disc drive resulting from an induced rotational vibration stimuli imparted on the first of the plurality of chassis;

(d10) imparting the induced rotational vibration stimuli on the first of the plurality of chassis systems by activating the first chosen selected disc drive to loop on an alternate full stroke seek cycles a predetermined number of the alternate full stroke seek cycles;

(d11) measuring and recording the energy level experienced by the first chosen selected disc drive resulting from the rotational vibration stimuli for each of the predetermined number of alternate full stroke seek cycles;

(d12) repeating steps (d7) through (d11) for each of the plurality of the selected disc drives mounted in each of the plurality of chassis for use in determining a rotational vibration index function used for evaluating the mechanical mounting environment in which the selected disc drives of the drive species are mounted; and

(d13) correlating the measured energy level for each of the plurality of disc drives mounted in each of the plurality of chassis to generate the rotational vibration index function for the drive species.

11. The method of claim 1 in which the rotational vibration index for the drive species of step (d) is derived from a rotational vibration index function that is based on a power spectral density profile specification for an individual disc drive of the drive species, and in which the measurement of the rotational vibration experienced by the disc drive of step (c) is used to determine a power spectral density reading, and further in which the rotational vibration index for the mechanical mounting environment with the sample disc drive mounted to the mechanical mounting environment of step (e) is derived by steps comprising:

(e1) supplying the power spectral density reading to a processor programmed with the rotational vibration index function for use in deriving the rotational vibration index for the mechanical mounting environment;

(e2) providing to the processor the power spectral density specification for an individual disc drive of the drive species; and

(e3) deriving the rotation vibration index for the mechanical mounting environment by applying the power spectral density reading and the power spectral specification to the rotational vibration index function and calculating the rotation vibration index for the mechanical mounting environment.

12. The method of claim 6 in which the data acquisition card of step (c2) is programmed with software for gathering, filtering, recording and displaying the frequency and the amplitude of rotation vibration experienced by the sample disc drive mounted in the mechanical mounting environment.

13. The method of claim 6 in which the computer with the data acquisition card communicating with the accelerometer of step (c3) is a test system, and in which the accelerometer is a pair of accelerometers, and further in which calibration of the test system comprises the steps of:

(a) applying power to the test system to determine operability of the pair of accelerometers;

(b) inducing a calibrated rotational vibration stimuli into the pair of accelerometers while monitoring the output signal from the accelerometers to determine a maximum peak value reported by each of the pair of accelerometers; and

(c) comparing the maximum peak value reported by each of the accelerometers to the other by calculating a ratio of the maximum peak value reported by a first of the pair of accelerometers raised to the third power to the maximum peak value reported by a second of the pair of accelerometers raised to the third power and verifying the ratio is within predetermined limits of between about 0.10 and 99.

14. A method for predicting performance of a disc drive of a drive species mounted in a mechanical mounting environment, the predicted performance of the disc drive based on a rotational vibration index derived from a measurement of an induced rotational vibration stimulus of the mechanical mounting environment by steps comprising:

(a) providing the disc drive selected from the drive species, the disc drive having a pair of attached accelerometers for capturing and reporting a rotational vibration experienced by the disc drive mounted in the mechanical mounting environment;

(b) supplying a test system for measuring the rotational vibration experienced by the disc drive mounted in the mechanical mounting environment;

(c) calibrating the test system to assure substantial accuracy of the measurement made by the pair of accelerometers measuring the induced rotational vibration stimulus applied to the mechanical mounting environment;

(d) mounting the disc drive with attached accelerometers within the mechanical mounting environment, defining and executing a series of seek patterns to impart the induced rotational vibration stimulus to the mechanical mounting environment while acquiring, analyzing and saving the measurement made by the pair of accelerometers measuring the induced rotational vibration stimulus of the mechanical mounting environment;

(e) providing a rotational vibration index function for use in determining a rotational vibration index for the mechanical mounting environment, and providing a rotational vibration index for the drive species for use with the rotational vibration index function; and

(f) computing a rotational vibration index for the mechanical mounting environment using the rotational vibration index function applied to the saved measurement taken by the pair of accelerometers of the induced rotational vibration stimulus of the mechanical mounting environment.

15. The method of claim 14 further having steps comprising:

(g) comparing the computed rotational vibration index for the mechanical mounting environment with the rotational vibration index for the drive species;

(h) determining if the computed rotational vibration index of the disc drive mounted in the mechanical mounting environment is greater than the rotational vibration index for the drive species and issuing a warning for the computed rotational vibration index of the disc drive mounted in the mechanical mounting environment greater than the rotational vibration index for the drive species;

(i) deciding if each of the series of seek patterns of mounting step (d) has been executed and repeating steps (d) through (h) for each seek pattern remaining to be executed; and

(j) generating a report predicting performance of the disc drive of the drive species mounted in a mechanical mounting environment.

16. The method of claim 15 in which the disc drive of generating step (j) is selected from a plurality of disc drives of the drive species.

17. The method of claim 15 in which the test system of supplying step (b) comprises:

a computer with a data acquisition card communicating with the pair of accelerometers of providing step (a), the data acquisition card for acquiring and analyzing the measurement made by the pair of accelerometers of the induced rotational vibration stimulus of the mechanical mounting environment;

a storage device communicating with the computer for saving the measurement made by the pair of accelerometers of the induced rotational vibration stimulus of the mechanical mounting environment; and

software incorporating the rotational vibration index function of providing step (e) programmed into the computer and communicating with the data acquisition to compute the rotational vibration index for the mechanical mounting environment.

18. The method of claim 14 in which the rotational vibration index for the disc drive with attached accelerometers of step (f) is computed by steps comprising:

(f1) providing a power spectral density profile for the drive species across a predetermined frequency range for use in determining the rotational vibration index for the mechanical mounting environment;

(f2) determining a power spectral density profile of the rotational vibration stimulus imparted on the mechanical mounting environment at each measured frequency response of the rotational vibration stimulus using the software incorporating the rotational vibration index function;

(f3) calculating and combining a different power term of each of the power spectral density profile of the rotational vibration stimulus imparted on the mechanical mounting environment and the power spectral density profile for the drive species at each and for all measured frequency responses of the rotational vibration stimulus;

(f4) finding a ratio of a square root of an area under the power spectral density profile of the rotational vibration stimulus to a square root of an area under the power spectral density profile of the drive species; and

(f5) computing the rotational vibration index on log scale from the ratio of a square root of the area under the power spectral density profile of the rotational vibration stimulus to the square root of the area under the power spectral density profile of the drive species and the combined sum difference powered term for all measured frequency responses of the rotational vibration stimulus.

19. A test system for predicting the performance of a disc drive of a drive species mounted in a mechanical mounting environment comprising;

a pair of accelerometers attached to the disc drive for measuring a response of the disc drive to a rotational vibration stimuli imparted on the mechanical mounting environment;

a computer with a data acquisition card communicating with the pair of accelerometers, the data acquisition card for acquiring and analyzing the response of the disc drive to the rotational vibration stimuli imparted on the mechanical mounting environment as measured by the pair of accelerometers;

a storage device communicating with the computer for saving the measurements made by the pair of accelerometers measuring the response of the disc drive to the rotational vibration stimuli imparted on the mechanical mounting environment; and

software incorporating a rotational vibration index function programmed into the computer and communicating with the data acquisition card to compute a rotational vibration index for the mechanical mounting environment by steps for computing the rotational vibration index for the mechanical mounting environment.

20. The test system of claim 19 in which the steps for computing the rotational vibration index for the mechanical mounting environment are steps comprising:

(a) mounting the disc drive of the drive species into the mechanical mounting environment to determine the rotational vibration index for the mechanical mounting environment;

(b) attaching the pair of accelerometers to the disc drive to measure the response of the disc drive to the rotational vibration stimuli imparted on the mechanical mounting environment;

(c) inducing a predetermined rotational vibration stimuli into the mechanical mounting environment to evaluate the mechanical mounting environment'"'"'s response to the predetermined rotational vibration stimuli;

(d) collecting data from the pair of accelerometers attached to the disc drive for use in determining a rotational vibration index for the mechanical mounting environment;

(e) providing a rotational vibration index for the drive species for comparison with the determined rotational vibration index; and

(f) determining and comparing the rotational vibration index for the mechanical mounting environment with the rotational vibration index of the drive species to relate the rotational vibration stimuli of the mechanical mounting environment to the performance of the disc drive.

21. The test system of claim 20 in which the mechanical mounting environment of step (a) is a system chassis, which accommodates at least one disc drive, wherein the system chassis is selected from a group comprising a computer system, a server system and a mass storage system.

22. The test system of claim 20 in which the mechanical mounting environment of step (a) is a test system chassis.

23. The test system of claim 20 in which the disc drive operation of step (b) is an execution of a predetermined seek algorithm selected from a group of seek algorithms comprising an alternate full stroke seek algorithm and an x-n seek algorithm.

24. The test system of claim 20 in which the disc drive operation of step (b) is execution of a data write operation.

25. The test system of claim 20 in which step (b) comprises the steps of:

(b1) providing and attaching the pair of accelerometers to the disc drive for use in measuring a frequency and an amplitude of rotation vibration experienced by the disc drive mounted in the mechanical mounting environment;

(b2) supplying a computer with a data acquisition card communicating with the pair of accelerometers for gathering, filtering, recording and displaying the frequency and the amplitude of rotational vibration experienced by the sample disc drive mounted in the mechanical mounting environment;

(b3) calibrating the computer with the data acquisition card communicating with the accelerometer to ensure signal integrity; and

(b4) securing the sample disc drive within the mechanical mounting environment for use in relating rotational vibration stimuli of a mechanical mounting environment to the performance of the disc drive.

26. The test system of claim 20 in which the predetermined rotational vibration stimuli of inducing step (c) is provided by a predetermined seek algorithm executed by the disc drive.

27. The test system of claim 20 in which the disc drive of step (d) includes a rotatable disc surface and an adjacent read/write head for writing data to and reading data from the rotatable disc surface and in which the predetermined rotational vibration stimuli of inducing step (c) is provided by a predetermined seek algorithm for the sample disc drive and further wherein the collecting step (d) comprises the steps of:

(d1) gathering, filtering, recording and displaying the frequency and the amplitude of rotational vibration experienced by the sample disc drive mounted in the mechanical mounting environment resulting from the predetermined rotational vibration stimuli using the calibrated computer with the data acquisition card communicating with the accelerometer; and

(d2) writing a predetermined data to the rotatable disc surface while gathering, filtering, recording and displaying a level of data throughput and the level of non-recoverable errors encountered by the sample disc drive while writing the predetermined data to the rotatable disc surface, for use in determining the rotational vibration index for the mechanical mounting environment.

28. The test system of claim 20 in which the rotational vibration index for the drive species of step (e) is provided by steps comprising:

(e1) selecting a first of a plurality of disc drives with a basedeck supporting a spindle motor assembly having an axis of rotation from the drive species and mounting a pair of accelerometers on the selected disc drive to detect a rotational vibration in the axis of rotation of the spindle motor assembly;

(e2) securing the selected disc drive to a vibration test fixture calibrated to provide vibration stimuli of selectable frequencies and power spectral densities to the selected disc drive, the vibration test fixture for use in establishing vibrational tolerance limits for the drive species;

(e3) choosing and applying a first rotational vibration having a predetermined frequency and power spectral density to the basedeck while performing data transfer operations for use in determining the rotational vibration index for the drive species;

(e4) increasing the power spectral density of the rotational vibration to a point that all reported errors are recoverable errors to establish an upper limit tolerance of the selected disc drive for the frequency of the rotational vibration chosen;

(e5) selecting a subsequent rotational vibration having a predetermined frequency and power spectral density different from the first selected rotational vibration and applying the subsequent selected rotational vibration to the basedeck while performing data transfer operations for use in determining the rotational vibration index for the drive species; and

(e6) repeating steps (e1) through (e5) across a predetermined frequency band for a predetermined number of disc drives selected from the drive species for use in determining an upper tolerance limit for a power spectral density profile across the predetermined frequency band for use in determining a power spectral density profile specification across the predetermined frequency band for an individual disc drive of the drive species.

29. The test system of claim 28 in which the rotational vibration index for the drive species of step (e) further comprises the steps of:

(e7) choosing a first of a plurality of the selected disc drives of the drive species for use in determining the rotational vibration index for the drive species;

(e8) attaching the pair of accelerometers on the first chosen disc drive to detect a rotational vibration in the axis of rotation of the spindle motor assembly and mounting the first chosen disc drive into a first of a plurality of chassis systems;

(e9) connecting the pair of accelerometers to the computer with a data acquisition card to measure an energy level experienced by the chosen disc drive resulting from an induced rotational vibration stimuli imparted on the first of the plurality of chassis;

(e10) imparting the induced rotational vibration stimuli on the first of the plurality of chassis systems by activating the chosen disc drive to loop on an alternate full stroke seek cycle for a predetermined number of the alternate full stroke seek cycles;

(e11) measuring and recording the energy level experienced by the chosen disc drive resulting from the rotational vibration stimuli for each of the predetermined number of alternate full stroke seek cycles;

(e12) repeating steps (e7) through (e11) for each of the plurality of the selected disc drives mounted in each of the plurality of chassis for use in determining a rotational vibration index function used for evaluating the mechanical mounting environment in which the selected disc drives of the drive species are mounted; and

(e13) correlating the measured energy level for each of the plurality of disc drives mounted in each of the plurality of chassis to generate the rotational vibration index function for the drive species.

30. The test system of claim 20 in which the rotational vibration index for the drive species of step (e) is derived from a rotational vibration index function that is based on a power spectral density profile specification for an individual disc drive of the drive species, and in which the data from the pair of accelerometers of step (d) is used to determine a power spectral density reading, and further in which the rotational vibration index for the mechanical mounting environment of step (f) is derived by steps comprising:

(f1) supplying the power spectral density reading to a processor programmed with the rotational vibration index function for use in deriving the rotational vibration index for the mechanical mounting environment;

(f2) providing to the processor the power spectral density specification for the individual disc drive; and

(f3) deriving the rotation vibration index for the mechanical mounting environment by applying the power spectral density reading and the power spectral density specification to the rotational vibration index function and calculating the rotation vibration index for the mechanical mounting environment.