Method and apparatus to verify disc drive vibrational performance

• US 20030220751A1
• Filed: 05/19/2003
• Published: 11/27/2003
• Est. Priority Date: 05/22/2002
• Status: Abandoned Application

• Current Assignee: Seagate Technology LLC (Seagate Technology Holdings Plc)
• Original Assignee: Seagate Technology LLC (Seagate Technology Holdings Plc)
• Inventors: Yang, Yong, Liu, Xiong, Lim, Choon Kiat, Zambri, Razman, Toh, Michael Joo Chiang
• Application Number:
  US10/440,693
• Publication Number:
  US 20030220751A1
• Time in Patent Office: Days
• US Class Current: 702/56
• CPC Class Codes: G01M 7/00 Vibration-testing of structures; Shock-testing of structures G01M9/00 takes precedence
• CPC Class Codes: G11B 5/00 Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor G11B11/00 and G11B13/00 take precedence

Abstract

A method of testing a data storage system such that the data storage system meets vibration performance standards includes the step of adding a reference vibration signal having varying magnitudes into a servo loop of the data storage system to simulate external vibration. The method also includes the step of verifying the external vibration performance by using the simulated external vibration. The simulated external vibration is simulated rotational vibration. Also disclosed is a data storage system configured to implement the method.

Claims

1. A method of testing a data storage system such that the data storage system meets vibration performance standards, the method comprising:

adding a reference vibration signal having varying magnitudes into a servo loop of the data storage system to simulate external vibration; and

verifying the external vibration performance by using the simulated external vibration.

2. The method of claim 1, wherein adding the reference vibration signal to simulate external vibration further comprises adding the reference vibration signal to simulate rotational vibration (RV) and wherein verifying the external vibration performance further comprises verifying RV performance by using the simulated RV.

3. The method of claim 2, wherein the step of adding the reference vibration signal further comprises:

(a) setting a scale to a first value and collecting a first data throughput value, the scale varying the magnitude of the reference vibration signal;

(b) increasing the scale by a predetermined value and collecting a data throughput value at the increased scale;

(c) dividing the data throughput value at the increased scale by the first data throughput value to determine a percentage; and

(d) comparing the determined percentage to a predetermined percentage.

4. The method of claim 3 wherein when the determined percentage is greater than the predetermined percentage, the method further comprising repeating steps (b), (c) and (d) until the determined percentage is less than the predetermined percentage.

5. The method of claim 3 wherein when the determined percentage is less than the predetermined percentage, a RV value is calculated in terms of a correlation coefficient and the scale.

6. The method of claim 3, wherein when the determined percentage is equal to the predetermined percentage, a RV value is calculated in terms of a correlation coefficient and the scale.

7. The method of claim 2 wherein the step of verifying RV performance further comprises:

providing a scale, wherein varying a value of the scale varies the magnitude of the reference vibration signal;

determining a correlation coefficient; and

calculating RV with in terms of correlation coefficient and the scale.

8. The method of claim 7 wherein determining the correlation coefficient comprises:

deriving a formula for a non-repeatable run-out (NRRO) increment related to RV;

deriving a formula for the NRRO increment related to the scale of the reference vibration signal; and

determining the correlation coefficient in terms of RV and the scale.

9. The method of claim 8, wherein deriving the NRRO increment related to RV further comprises:

(a) installing a RV shaker to induce and vary RV levels in the data storage system;

(b) measuring a NRRO baseline, wherein the NRRO baseline is the NRRO of the data storage system with no induced RV by the RV shaker;

(c) increasing the RV level to an increased RV level and collecting NRRO at the increased RV level;

(d) calculating the NRRO increment by subtracting the NRRO baseline from the NRRO collected at the increased RV level;

(e) repeating steps (c) and (d) until the NRRO increment exceeds a predetermined percentage of track pitch; and

(f) plotting NRRO increment calculated in step (e) versus RV.

10. The method of claim 8, wherein deriving the NRRO increment related to the scale further comprises:

(a) adding the reference vibration signal to the servo loop;

(b) setting the scale to zero;

(c) collecting a NRRO baseline value;

(d) increasing the scale by a predetermined value and collecting a NRRO value at the increased scale;

(e) calculating the NRRO increment by subtracting the NRRO baseline value from the NRRO value collected at the increased scale;

(f) repeating steps (d) and (e) until the NRRO increment exceeds a predetermined percentage of track pitch; and

(g) plotting the NRRO increment calculated from step (e) versus the scale.

11. A data storage system configured to verify vibrational performance, the data storage system having a servo system, the servo system comprising:

reference vibration signal generating circuitry which generates a reference vibration signal;

a servo loop coupled to the reference vibration signal generating circuitry, the servo loop configured to generate a control signal, as a function of the reference vibration signal, to drive a voice coil motor of the data storage system, and to thereby test the vibrational performance of the data storage system.

12. The data storage system of claim 11, wherein the servo loop is configured to generate a position error signal, and to combine the reference vibration signal and the position error signal to generate the control signal.

13. The data storage system of claim 12, wherein the voice coil motor is part of drive actuator mechanics, the drive actuator mechanics comprising part of the servo loop and further including read/write heads which read data and servo information from a storage medium of the data storage system.

14. The data storage system of claim 13, wherein the drive actuator mechanics are configured to generate a head position signal, and wherein the position error signal is calculated by subtracting the head position signal from a written-in error.

15. The data storage system of claim 13, wherein the servo loop further comprises a servo controller which receives the combined position error signal and reference vibration signal as an input, and which generates the control signal in response.

16. A vibrational testing system including the data storage system of claim 13, the vibrational testing system further comprising a host computing device coupled to the drive actuator mechanics through a read/write channel of the data storage system, the host computing device receiving data from the read/write channel, which was read from the storage medium while the reference vibration signal was provided to the servo loop, in order to monitor data throughput to verify vibrational performance of the data storage system.

17. The data storage system of claim 11, wherein the reference vibration signal simulates a rotational vibration of the data storage system.

18. A data storage system configured to verify vibrational performance, the data storage system having a servo system, the servo system comprising:

means for generating a reference vibration signal; and

a servo loop coupled to the means for generating the reference vibration signal, the servo loop configured to generate a control signal, as a function of the reference vibration signal, to drive a voice coil motor of the data storage system, and to thereby test the vibrational performance of the data storage system.

19. The data storage system of claim 18, wherein the means for generating the reference vibration signal further comprises:

filter circuitry which receives a random noise signal as an input, and generates an initial reference vibration signal as an output; and

scale circuitry coupled to the filter and configured to multiply the initial reference vibration signal by a scaling factor to generate the reference vibration signal.

20. The data storage system of claim 18, wherein the reference vibration signal simulates a rotational vibration of the data storage system.