In-situ testing of a MEMS accelerometer in a disc storage system

• US 6,629,448 B1
• Filed: 01/19/2001
• Issued: 10/07/2003
• Est. Priority Date: 02/25/2000
• Status: Expired due to Fees

• Current Assignee: Seagate Technology LLC (Seagate Technology Holdings Plc)
• Original Assignee: Seagate Technology LLC (Seagate Technology Holdings Plc)
• Inventors: Cvancara, Dustin M.
• Primary Examiner(s): RAEVIS, ROBERT R
• Application Number:
  US09/766,285
• Time in Patent Office: 991 Days
• Field of Search: 73/13.7, 73/13.8, 73/14.1
• US Class Current: 73/1.38
• CPC Class Codes: G01P 15/08 with conversion into electric or magnetic values
• CPC Class Codes: G01P 21/00 Testing or calibrating of apparatus or devices covered by the preceding groups

Abstract

A disc storage system performing an in-situ test on a MEMS accelerometer, in a disc drive. The circuit includes a control circuit that establishes a desired self test condition conducive to the in-situ test during a self test interval. The circuit includes a stored reference representing at least one characteristic limit of an integrity output of the, MEMS accelerometer. The circuit includes a test circuit that receives the integrity output value and the stored reference during the in-situ test interval and that generates an in-situ test output representative of integrity of the MEMS accelerometer. Damaged or degraded MEMS accelerometers can be diagnosed in-situ.

Claims

1. A disc storage system including a circuit for performing an in-situ self test on a MEMS accelerometer that is coupled to the disc storage system, the circuit comprising:

a controller configured to apply a self test input comprising a duty cycle control signal to the MEMS accelerometer during a self test interval to establish a self test condition that comprises a simulated acceleration induced by the duty cycle control signal;

a stored reference representative of at least one characteristic limit of an integrity output of the MEMS accelerometer; and

a test circuit configured to receive at least one MEMS integrity output value from the MEMS accelerometer during the self test interval and to generate an in-situ test output representative of integrity of the MEMS accelerometer subject to the simulated acceleration induced by the duty cycle control signal and based on the MEMS integrity output value and the stored reference.

2. The disc storage system of claim 1 wherein the test circuit successively compares each of a plurality of integrity values with at least one characteristic limit.

3. The disc storage system of claim 1 wherein the test circuit averages a plurality of successive samples of the integrity output.

4. The disc storage system of claim 1 further comprising:

a self-test switch circuit coupled to the controller wherein activation of the self-test switch defines the in-situ test interval.

5. The disc storage system of claim 1 wherein the MEMS accelerometer provides closed loop acceleration feedback during a normal operation interval, and the closed loop feedback is disabled during the self test interval to establish the desired self test condition.

6. The disc storage system of claim 1 wherein the MEMS accelerometer has an acceleration output that is coupled to a controller controlling the position of the read/write head assembly, the MEMS accelerometer providing rotational vibration feedforward compensation to the controller.

7. The disc storage system of claim 1 wherein the self test condition comprises a simulated acceleration and the integrity output of the MEMS accelerometer comprises an acceleration output of the MEMS accelerometer.

8. The disc storage system of claim 1 wherein the self test condition comprises disabling calibration of the MEMS accelerometer.

9. A method of performing an in-situ test on a MEMS accelerometer in a disc storage system, comprising:

(a) establishing a self test condition conducive to performing an in-situ self test during a self test interval, the self test condition including simulating acceleration by applying of a duty cycle control signal to the MEMS accelerometer;

(b) storing a reference value representing a reference limit of an integrity output of the MEMS accelerometer;

(c) receiving the integrity output and the stored reference value during the self test interval at a test circuit; and

(d) generating an integrity-indicative test output in the test circuit when the simulated acceleration induced by the duty cycle control signal is applied.

10. The method of claim 9, further comprising:

(e) successively comparing a plurality of integrity values with a plurality of characteristic limits in the test circuit.

11. The method of claim 10, further comprising:

(f) averaging a plurality of successive samples of the integrity output in the test circuit.

12. The method of claim 11, further comprising:

(g) activating a self-test switch coupled to the control circuit; and

(h) defining the in-situ test interval as a function of the self-test switch activation.

13. The method of claim 9, further comprising:

(e) providing closed loop feedback of a read/write head position during a normal operation interval, and

(f) disabling the closed loop feedback during the self test interval to establish the desired condition.

14. The method of claim 9, further comprising:

(e) mounting the accelerometer on the disc storage system, and

(f) coupling an output of the accelerometer to a controller controlling the position of the read/write head assembly during a normal operation interval.

15. The method of claim 9, further comprising:

(e) mounting the accelerometer on a frame of a disc drive; and

(f) providing a warning of acceleration of the disc drive frame as a function of an output of the accelerometer.

16. The method of claim 9, further comprising:

(e) disabling calibration of the integrity output to establish the in-situ condition.

17. The method of claim 9 further comprising (e) storing a plurality of sequences of instructions describing steps (a), (c) and (d) on a computer readable medium, the plurality of sequences of instructions including sequences which, when executed by a processor in the disc storage system, cause the processor to perform the in-situ test.

18. A disc storage system including a circuit for performing an in-situ test on a MEMS accelerometer, comprising:

a stored reference representative of at least one characteristic limit of an integrity output of the MEMS accelerometer; and

means for generating an in-situ test output representative of integrity of the MEMS accelerometer based upon the MEMS integrity output value when a simulated acceleration is induced by a duty cycle control signal and the stored reference.