Self-test in a closed-loop vibratory gyroscope

Patent metadata

Field	Value
Publication number	US-9846037-B2
Application number	US-201514753417-A
Country	US
Kind code	B2
Filing date	Jun 29, 2015
Priority date	Jun 30, 2014
Publication date	Dec 19, 2017
Grant date	Dec 19, 2017

Abstract

A closed-loop microelectromechanical gyroscope with a self-test function. At least one test input signal is generated from a signal of the vibrational primary motion and input during operation of the microelectromechanical gyroscope to the sense circuit.

First claim

The invention claimed is:

1. A microelectromechanical gyroscope, comprising:
a body;
a drive element suspended to the body for vibrational primary motion in a first direction;
a drive circuit, wherein the drive element is configured to input into the drive circuit a drive sense signal that corresponds to the vibrational primary motion of the drive element, and wherein the drive circuit is configured to generate from the drive sense signal a timing signal and a primary signal corresponding to the vibrational primary motion;
a sense element coupled to the drive element and configured to receive an orthogonal Coriolis force component in a second direction, wherein the second direction is perpendicular to the first direction;
a sense circuit configured to output a sense signal that corresponds to forces acting on the sense element in the second direction, and to produce a sense feedback signal to control the vibrational secondary motion of the sense element;
a test circuit, including:
a test signal generator configured to receive from the drive circuit the primary signal and the timing signal, to generate from the primary signal at least one test input signal comprising the primary signal modulated with at least one test frequency signal, the period of each of the at least one test frequency signals being a multiple of a primary period of the timing signal, and to output the test input signal during operation of the microelectromechanical gyroscope to the sense circuit; and

a self-test analyzer configured to extract from the sense signal at least one test output signal that results from the at least one test input signal, and to determine validity of at least one operating parameter of the microelectromechanical gyroscope on a basis of the test output signal.

2. A microelectromechanical gyroscope according to claim 1 , wherein the sense element includes a transducer configured to convert the sense feedback signal into a force component in the second direction.

3. A microelectromechanical gyroscope according to claim 1 , wherein
the sense element has a resonant frequency equal to a resonant frequency of the drive element; and wherein
the sense circuit includes a low pass filter with a frequency response function that is configured to peak in the mechanical resonant frequency of the sense element.

4. A microelectromechanical gyroscope according to claim 1 , wherein
a closed loop gain of the sense circuit varies as a function of frequency; and wherein
the test input signals are adjusted to a range where the loop gain is between −6 and 6 dB.

5. A microelectromechanical gyroscope according to claim 4 , wherein the test input signals are adjusted to a range where the loop gain is between −3 and 3 dB.

6. A microelectromechanical gyroscope according to claim 1 , wherein
the test signal generator is configured to input a primary signal in phase with the vibrational primary motion of the drive element,
wherein the test signal generator is configured to generate at least one test frequency signal such that a cycle of the at least one test frequency signal is a constant integer multiple of a cycle of the vibrational primary motion,
and wherein the test signal generator is configured to generate the test input signal by modulating the primary signal with the at least one test frequency signal.

7. A microelectromechanical gyroscope according to claim 1 , wherein
the test signal generator is configured to input a primary signal in phase with the vibrational primary motion of the drive element,
wherein the test signal generator is configured to generate at least one test frequency signal such that a cycle of the at least one test frequency signal is a constant multiple of a cycle of the vibrational primary motion,
and wherein the test signal generator is configured to use the at least one test frequency signal as the test input signal.

8. A microelectromechanical gyroscope according to claim 1 , wherein the self test analyzer comprises:
a first demodulator configured to create a first output signal by demodulating the sense signal with the primary signal;
a second demodulator configured to create a second output signal by demodulating the first output signal with the test frequency signal;
a test signal analyzer configured to determine validity of the at least one operating parameter of the microelectromechanical gyroscope on a basis of the second output signal.

9. A microelectromechanical gyroscope according to claim 1 , wherein the primary signal includes components in phase with at least one of position or velocity of a mass undergoing the vibrational primary motion in the drive element.

10. A microelectromechanical gyroscope according to claim 1 , wherein the test input signal is input to a front end part of the sense circuit.

11. A microelectromechanical gyroscope according to claim 1 , wherein the test input signal is input into the sense circuit after a front end part of the sense circuit.

12. A microelectromechanical gyroscope according to claim 1 , wherein the test signal generator is configured to create at least two test output signals, and the test signal analyzer is configured to determine validity of the at least one operating parameter of the microelectromechanical gyroscope on a basis of both of the at least two test output signals.

13. A microelectromechanical gyroscope according to claim 12 , wherein the test signal generator is configured to create two test output signals, and the operating parameter is deemed invalid if both of the test output signals are invalid.

14. A microelectromechanical gyroscope according to claim 1 , wherein the test signal analyzer is configured to create an alarm in response to the at least one operating parameter being determined invalid.

15. A microelectromechanical gyroscope according to claim 1 , wherein the test signal analyzer is configured to store a triggering condition for the at least one test output signal, and to determine the at least one operating parameter invalid in response to the one test output signal not fulfilling its triggering condition.

16. A microelectromechanical gyroscope according to claim 15 , wherein the test signal analyzer is configured to store a triggering condition for two or more test output signals, and to determine the at least one operating parameter invalid based on whether the two or more test output signals fulfil their respective triggering conditions.

17. A microelectromechanical gyroscope according to claim 16 , wherein the test signal analyzer is configured to store a triggering condition for two test output signals, and to determine at least one operating parameter invalid if both of the two test output signals fails to fulfil their respective triggering conditions.

18. A microelectromechanical gyroscope according to claim 15 , wherein the triggering condition or each of the triggering conditions include a range for values of its respective test output signal.

19. A microelectromechanical gyroscope according to claim 18 , wherein in response to a test output signal failing to fulfil its respective triggering condition, the test signal analyzer is configured to check whether a similar failure has occurred previously, and to determine an error condition only if a similar failure has occurred previously for a predefined number of times.

20. A microelectromechanical gyroscope according to claim 19 , wherein in a positive group of similar failures, values of the test output signal exceed an upper threshold of the range, and in

Assignees

• Murata Manufacturing Co

Inventors

• Aaltonen Lasse

Classifications

• G01C19/5726

  Signal processing · CPC title

• G01C19/5776 Primary

  Signal processing not specific to any of the devices covered by groups G01C19/5607 - G01C19/5719 · CPC title

• G01C19/5762 Primary

  the sensing mass being connected to a driving mass, e.g. driving frames · CPC title

• G01C19/5755

  the devices having a single sensing mass · CPC title

• G01P21/00

  Testing or calibrating of apparatus or devices covered by the preceding groups · CPC title