Microelectromechanical gyroscope with suppression of capacitive coupling spurious signals and control method

• US 7,827,864 B2
• Filed: 02/13/2008
• Issued: 11/09/2010
• Est. Priority Date: 02/13/2007
• Status: Active Grant

• Current Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Inventors: Lasalandra, Ernesto, Caminada, Carlo, Prandi, Luciano
• Primary Examiner(s): Williams; Hezron
• Assistant Examiner(s): Shah; Samir M
• Application Number:
  US12/030,729
• Publication Number:
  US 20080190198A1
• Time in Patent Office: 1,000 Days
• Field of Search: 735/033, 735/040.2, 735/040.8, 735/041.2, 735/041.8
• US Class Current: 73/504.18
• CPC Class Codes: G01C 19/5726 Signal processing
• CPC Class Codes: G01C 19/5762 the sensing mass being connected to a driving mass, e.g. driving frames

Abstract

A microelectromechanical gyroscope having a microstructure with a first mass, which can oscillate according to a first axis, and a second mass constrained to the first mass so as to oscillate according to a second axis in response to a rotation of the microstructure, and a driving device coupled to the microstructure to maintain the first mass in oscillation at a resonance frequency, the driving device provided with a low-pass filter having a passband such that the resonance frequency is in the passband and a disturbance frequency associated with disturbance signals due to coupling between the first mass and the second mass is not in the passband.

Claims

1. A microelectromechanical gyroscope comprising:

a microstructure, including a first mass and a second mass, wherein the first mass is oscillatable about a first axis with a resonance frequency and the second mass is constrained to the first mass so as to be drawn along by the first mass about the first axis and to oscillate about a second axis in response to a rotation of the microstructure; and

a driving device, coupled to the microstructure so as to form a feedback control loop that includes the first mass and configured to maintain the first mass in oscillation at the resonance frequency, the driving device comprising a trans-conductance amplifier that generates detection voltages followed by a low-pass filter having a passband of frequencies and transfer function such that the resonance frequency is in the passband and a disturbance frequency associated with disturbance signals due to electrical coupling between the first mass and the second mass is not in the passband, the low-pass filter followed by a derivative stage having a transfer function that eliminates offsets, including offsets introduced by the trans-conductance amplifier.

2. The gyroscope of claim 1, wherein an attenuation of the low-pass filter at the disturbance frequency is at least −

20 dB.

3. The gyroscope of claim 2, wherein the attenuation of the low-pass filter at the disturbance frequency is at least −

30 dB.

4. The gyroscope of claim 1, wherein the transfer function of the low-pass filter is

5. The gyroscope of claim 4, wherein the natural frequency of the low-pass filter is approximately 160 krad/s.

6. The gyroscope of claim 1, wherein the low-pass filter has substantially unitary gain at the resonance frequency.

7. The gyroscope of claim 1, wherein the low-pass filter introduces a phase offset not greater than 2°

at the resonance frequency.

8. The gyroscope of claim 1, wherein the low-pass filter has a figure of merit not lower than 10.

9. The gyroscope of claim 1, wherein the low-pass filter is a second-order Chebyshev filter.

10. The gyroscope of claim 1, wherein the low-pass filter is of a multiple-feedback type.

11. The gyroscope of claim 1, wherein the driving device comprises a derivative stage cascaded to the low-pass filter.

12. A method for controlling a microelectromechanical gyroscope, comprising:

providing a microstructure including a first mass, oscillatable about a first axis with a resonance frequency, and a second mass;

constraining the second mass to the first mass so that the second mass is drawn along by the first mass about the first axis and oscillates about a second axis in response to a rotation of the microstructure; and

feedback controlling a velocity of the first mass to maintain the first mass in oscillation at the resonance frequency, the step of feedback controlling comprising generating detection voltages with a trans-conductance amplifier, low-pass filtering with a low-pass filter having a passband of frequencies such that the resonance frequency is in the passband and a disturbance frequency associated with disturbance signals due to coupling between the first mass and the second mass is not in the passband, and following the low-pass filter with a derivative stage that eliminates offsets, including offsets introduced by the trans-conductance amplifier.

13. A circuit for use with a microstructure having a first mass and a second mass, the circuit comprising:

a driving circuit coupled to the first mass and configured to maintain the first mass in oscillation at a resonance frequency, the driving circuit including a low-pass filter having a pass band of frequencies that include the resonance frequency in the pass band and that exclude a disturbance frequency associated with disturbance signals generated from electrical coupling between the first mass and the second mass, the low-pass filter having a transfer function

14. The circuit of claim 13, wherein the low-pass filter comprises one of a second-order Chebyshev filter, a Butterworth filter, and a multiple-feedback type filter.

15. The circuit of claim 13, wherein the low-pass filter has a natural frequency in the range of 120 krad/s and 200 krad/s and substantially unitary gain at the resonance frequency.

16. A system, comprising:

a control unit; and

a microelectromechanical gyroscope coupled to the control unit, the microelectromechanical gyroscope comprising;

a first mass and a second mass that moves in response to movement of the first mass; and

a driving circuit coupled to the first mass and configured to maintain the first mass in oscillation at a resonance frequency, the driving circuit including a trans-conductance amplifier followed by a series connected low-pass filter and a derivative stage, the low-pass filter having a pass band of frequencies that include the resonance frequency in the pass band and that exclude a disturbance frequency associated with disturbance signals generated from electrical coupling between the first mass and the second mass and the derivative stage structured to eliminate offsets in the system, including offsets introduced by the trans-conductance amplifier.

17. The circuit of claim 16, wherein the low-pass filter comprises one of a second-order Chebyshev filter, a Butterworth filter, and a multiple-feedback type filter.

18. The circuit of claim 16, wherein the low-pass filter has a natural frequency in the range of 120 krad/s and 200 krad/s and substantially unitary gain at the resonance frequency.

19. The circuit of claim 18, wherein the low-pass filter has a transfer function