MICROELECTROMECHANICAL GYROSCOPE WITH SELF-CALIBRATION FUNCTION AND METHOD OF CALIBRATING A MICROELECTROMECHANICAL GYROSCOPE

• US 20130031950A1
• Filed: 10/09/2012
• Published: 02/07/2013
• Est. Priority Date: 07/28/2011
• Status: Active Grant

• Current Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Inventors: Ungaretti, Tommaso, Caminada, Carlo, Prandi, Luciano, Donadel, Andrea
• Granted Patent: US 9,212,910 B2
• Time in Patent Office: Days
• US Class Current: 73/1.77
• CPC Class Codes: G01C 19/5776 Signal processing not specific to any of the devices covered by groups G01C19/5607 - G01C19/5719

Abstract

A microelectromechanical gyroscope having a supporting structure; a mass capacitively coupled to the supporting structure and movable with a first degree of freedom and a second degree of freedom, in response to rotations of the supporting structure about an axis; driving components, for keeping the mass in oscillation according to the first degree of freedom; a read interface for detecting transduction signals indicating the capacitive coupling between the mass and the supporting structure; and capacitive compensation modules for modifying the capacitive coupling between the mass and the supporting structure. Calibration components detect systematic errors from the transduction signals and modify the capacitive compensation modules as a function of the transduction signals so as to attenuate the systematic errors.

Claims

1. A microelectromechanical gyroscope, comprising:

a supporting structure having sensing terminals;

a capacitive coupling coupled to the sensing terminals;

a sensing mass coupled to the supporting structure through the capacitive coupling, the sensing mass being movable with respect to the supporting structure according to a first degree of freedom and being movable with respect to the supporting structure according to a second degree of freedom in response to rotations of the supporting structure about an axis;

driving components configured to maintain the sensing mass in oscillation according to the first degree of freedom;

a reading interface connected to the sensing terminals and configured to sense transduction signals indicative of the capacitance between the sensing mass and the supporting structure; and

capacitive compensation modules connected to the sensing terminals and configured to compensate for a capacitance of the capacitive coupling between the sensing mass and the supporting structure; and

calibration components coupled to the reading interface and configured to detect systematic errors from the transduction signals and to adjust the capacitive compensation modules as a function of the transduction signals to mitigate the systematic errors.

2. The gyroscope according to claim 1, further comprising a control unit configured to selectively activate and deactivate the driving components.

3. The gyroscope according to claim 2, wherein the calibration components include a processing module configured to determine a compensation value of the capacitive compensation modules as a function of the transduction signals.

4. The gyroscope according to claim 3, wherein:

the processing module is configured to determine an offset compensation value in a first mode of operation, the driving components are deactivated by the control unit during the first mode of operation;

the capacitive compensation modules include offset capacitive compensation modules; and

the control unit is configured to adjust the offset capacitive compensation modules as a function of the offset compensation value.

5. The gyroscope according to claim 4, wherein:

the calibration components include a low-pass filter coupled to the reading interface, the low-pass filter being configured to receive the transduction signals from the reading interface and to provide filtered transduction signals; and

the processing module is configured to determine an offset compensation value on the basis of the filtered transduction signals in a second mode of operation, the driving components are activated by the control unit during the second mode of operation.

6. The gyroscope according to claim 4, wherein:

the processing module is configured to determine a quadrature compensation value in a second mode of operation, the driving components are activated by the control unit during the second mode of operation;

the capacitive compensation modules include quadrature capacitive compensation modules; and

the control unit is configured to adjust the quadrature capacitive compensation modules as a function of the quadrature compensation value.

7. The gyroscope according to claim 6, wherein:

the driving components are configured to provide a main clock signal synchronous with oscillations of the sensing mass and a quadrature clock signal that is 90°

out of phase with respect to the main clock signal;

the calibration components include a demodulator configured to demodulate the transduction signals using the quadrature clock signal and to provide demodulated transduction signals; and

the processing module is configured to determine the quadrature compensation value as a function of the demodulated transduction signals.

8. The gyroscope according to claim 7, wherein the demodulator is selectively connectable between the reading interface and the processing module.

9. The gyroscope according to claim 1, further comprising a processing chain coupled to the reading interface, the processing chain configured to generate output signals as a function of the transduction signals.

10. The gyroscope according to claim 9, wherein at least some of the calibration components are shared with the processing chain.

11. The gyroscope according to claim 9, wherein the calibration components are distinct from the processing chain.

13. The system of claim 1 wherein the control unit is configured to selectively activate and deactivate the driving components.

12. An electronic system, comprising:

a control unit, and

a gyroscope coupled to the control unit, the gyroscope, including;

a supporting structure having sensing terminals;

a capacitive coupling coupled to the sensing terminals;

a sensing mass coupled to the supporting structure through the capacitive coupling, the sensing mass being movable with respect to the supporting structure according to a first degree of freedom and being movable with respect to the supporting structure according to a second degree of freedom in response to rotations of the supporting structure about an axis;

driving components configured to maintain the sensing mass in oscillation according to the first degree of freedom;

a reading interface connected to the sensing terminals and configured to sense transduction signals indicative of the capacitance between the sensing mass and the supporting structure; and

capacitive compensation modules connected to the sensing terminals and configured to compensate for a capacitance of the capacitive coupling between the sensing mass and the supporting structure; and

calibration components coupled to the reading interface and configured to detect systematic errors from the transduction signals and to adjust the capacitive compensation modules as a function of the transduction signals to mitigate the systematic errors.

14. The system of claim 12, wherein:

the processing module is configured to determine an offset compensation value in a first mode of operation, the driving components are deactivated by the control unit during the first mode of operation;

the capacitive compensation modules comprise offset capacitive compensation modules; and

the control unit is configured to adjust the offset capacitive compensation modules as a function of the offset compensation value.

15. The system of claim 14, wherein:

the processing module is configured to determine a quadrature compensation value in a second mode of operation, the driving components are activated by the control unit during the second mode of operation;

the capacitive compensation modules include quadrature capacitive compensation modules; and

the control unit is configured to adjust the quadrature capacitive compensation modules as a function of the quadrature compensation value.

16. The system of claim 15, wherein:

the driving components are configured to provide a main clock signal synchronous with oscillations of the sensing mass and a quadrature clock signal that is 90°

out of phase with respect to the main clock signal;

the calibration components include a demodulator configured to demodulate the transduction signals using the quadrature clock signal and to provide demodulated transduction signals; and

the processing module is configured to determine the quadrature compensation value as a function of the demodulated transduction signals.

17. The system of claim 14, wherein:

the calibration components include a low-pass filter coupled to the reading interface, the low-pass filter being configured to receive the transduction signals from the reading interface and to provide filtered transduction signals; and

the processing module is configured to determine an offset compensation value on the basis of the filtered transduction signals in a second mode of operation, the driving components are activated by the control unit during the second mode of operation.

18. A method, comprising:

calibrating a microelectromechanical gyroscope, the calibrating including;

oscillating a sensing mass in a first degree of freedom with driving components;

sensing through a reading interface transduction signals indicative of capacitive coupling between the sensing mass and supporting structure, the sensing mass being movable with respect to the supporting structure according to the first degree of freedom and being movable with respect to the supporting structure according to a second degree of freedom in response to rotations of the supporting structure about an axis; and

compensating for a capacitance of the capacitive coupling between the sensing mass and the supporting structure by;

incorporating calibration components in the gyroscope;

coupling the calibration components to the reading interface;

detecting systematic errors from transduction signals; and

adjusting the capacitive compensation modules as a function of the transduction signals, so as to mitigate the systematic errors.

19. The method according to claim 18, wherein detecting systematic errors from the transduction signals includes deactivating the driving components during a first mode of operation, and sensing the transduction signals with the driving components deactivated.

20. The method according to claim 19, wherein detecting systematic errors from transduction signals includes:

activating the driving components and the transduction signals during a second mode of operation;

providing a main clock signal, synchronous with the oscillations of the sensing mass, and a quadrature clock signal, 90°

out of phase with respect to the main clock signal; and

demodulating the transduction signals V_T) using the quadrature clock signal.