MICROELECTROMECHANICAL DEVICE INCORPORATING A GYROSCOPE AND AN ACCELEROMETER

• US 20130125649A1
• Filed: 09/12/2012
• Published: 05/23/2013
• Est. Priority Date: 09/12/2011
• Status: Active Grant

• Current Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Inventors: Simoni, Barbara, Valzasina, Carlo
• Granted Patent: US 9,234,913 B2
• Time in Patent Office: Days
• US Class Current: 73/504.04
• CPC Class Codes: G01C 19/574 the devices having two sensing masses in anti-phase motion
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 15/18 in two or more dimensions

Abstract

A microelectromechanical device includes: a supporting structure; two sensing masses, movable with respect to the supporting structure according to a first axis and a respective second axis; a driving device for maintaining the sensing masses in oscillation along the first axis in phase opposition; sensing units for supplying sensing signals indicative of displacements respectively of the sensing masses according to the respective second axis; processing components for combining the sensing signals so as to: in a first sensing mode, amplify effects on the sensing signals of concordant displacements and attenuate effects of discordant displacements of the sensing masses; and in a second sensing mode, amplify effects on the sensing signals of discordant displacements and attenuate effects of concordant displacements of the sensing masses.

Claims

1. A microelectromechanical device, comprising:

a supporting structure;

a first sensing mass and a second sensing mass, movable with respect to the supporting structure both according to a first axis and each according to a respective second axis, perpendicular to the first axis;

a driving device configured to maintain the first sensing mass and the second sensing mass in oscillation along the first axis in phase opposition;

a first group of sensors and a second group of sensors configured to supply sensing signals indicative of displacements of the first sensing mass and of second sensing mass, respectively according to the second axis;

processing components configured to;

combine the sensing signals in a first sensing mode and in a second sensing mode,

amplify in the first sensing mode, effects on the sensing signals of concordant displacements and to attenuate effects of discordant displacements of the first sensing mass and of the second sensing mass; and

amplify in the second sensing mode, effects on the sensing signals of discordant displacements and to attenuate effects of concordant displacements of the first sensing mass and of the second sensing mass.

2. A device according to claim 1, wherein the processing components are configured to:

combine the sensing signals,

add in the first sensing mode, effects on the sensing signals of displacements of the first sensing mass and of the second sensing mass caused by accelerations of the supporting structure along a sensing axis perpendicular to the first axis and attenuate effects on the sensing signals of displacements of the first sensing mass and of the second sensing mass caused by rotations of the supporting structure about a third axis perpendicular to the first axis in combination with the oscillations according to the first axis; and

add in the second sensing mode, effects on the sensing signals of displacements of the first sensing mass and of the second sensing mass caused by rotations of the supporting structure about the third axis in combination with the oscillations along the first axis and attenuate effects of the sensing signals of displacements of the first sensing mass and of the second sensing mass caused by accelerations of the supporting structure according to the sensing axis.

3. A device according to claim 1, wherein the first group of sensors and the second group of sensors are capacitive sensors and are configured to present concordant capacitance variations in response to concordant displacements of the first sensing mass and of the second sensing mass and discordant capacitance variations in response to discordant displacements of the first sensing mass and of the second sensing mass.

4. A device according to claim 3, wherein the first group of sensors and the second group of sensors are differential sensors.

5. A device according to claim 3, comprising a differential sensing interface and a routing stage, configured to invert the connection of one of the first group of sensors and the second group of sensors to inputs of the sensing interface between the first sensing mode and the second sensing mode.

6. A device according to claim 3, wherein the first sensing mass and the second sensing mass are constrained to the supporting structure to translate along the second axis.

7. A device according to claim 6, wherein the first group of sensors and the second group of sensors comprise respective first and second fixed sensing electrodes that are anchored to the supporting structure, and respective movable sensing electrodes each anchored to one of the first sensing mass and the second sensing mass, respectively, and interposed between the first fixed sensing electrodes and second fixed sensing electrodes, respectively.

8. A device according to claim 7, wherein the first group of sensors and the second group of sensors are parallel plate capacitors and the first and second fixed sensing electrodes and the movable sensing electrodes are perpendicular to the second axis.

9. A device according to claim 3, wherein the first sensing mass and the second sensing mass are constrained to the supporting structure to rotate about rotation axes.

10. A device according to claim 9, wherein:

the first group of sensors and the second group of sensors comprise respective first and second fixed sensing electrodes and respective first and second movable sensing electrodes;

the first and second movable sensing electrodes are arranged on surfaces of the respective one of the first sensing mass and the second sensing mass, facing the supporting structure;

the first and second moveable electrodes of the first sensing mass and of the second sensing mass, respectively, are positioned at opposite sides of the respective rotation axes.

11. A device according to claim 1, comprising a third sensing mass and a fourth sensing mass, movable with respect to the supporting structure according to a third auxiliary axis perpendicular to the first axis and according to the second axis perpendicular to the first axis.

12. A device according to claim 11, wherein the third sensing mass and the fourth sensing mass are mechanically coupled to the first sensing mass and to the second sensing mass through elastic coupling elements that are configured to propagate the oscillations from the first sensing mass and from the second sensing mass to the third sensing mass and to the fourth sensing mass, the third sensing mass and the fourth sensing mass being configured to oscillate in phase opposition according to the auxiliary axis.

13. A device according to claim 11, comprising a third group of sensors and a fourth group of sensors, configured to supply sensing signals indicative of displacement of the third sensing mass and of the fourth sensing mass, respectively according to the second axis.

14. A device according to claim 1, comprising, for each sensing mass, a further group of sensors, for sensing displacements of the respective sensing mass according to a further axis.

15. An electronic system, comprising:

a control unit; and

a microelectromechanical sensor coupled to the control unit, the sensor including;

a supporting structure;

a first sensing mass and a second sensing mass, movable with respect to the supporting structure according to a first axis and according to a second axis, perpendicular to the first axis;

a driving device configured to maintain the first sensing mass and the second sensing mass in oscillation along the first axis in phase opposition;

a first group of sensors and a second group of sensors configured to supply sensing signals indicative of displacements of the first sensing mass and of second sensing mass, respectively according to the second axis;

processing components, configured to;

combine the sensing signals in a first sensing mode and in a second sensing mode,

amplify in the first sensing mode, effects on the sensing signals of concordant displacements and attenuate effects of discordant displacements of the first sensing mass and of the second sensing mass; and

amplify in the second sensing mode, effects on the sensing signals of discordant displacements and attenuate effects of concordant displacements of the first sensing mass and of the second sensing mass.

16. A system according to claim 15, wherein the first group of sensors and the second group of sensors are capacitive sensors and are configured to present concordant capacitance variations in response to concordant displacements of the first sensing mass and of the second sensing mass and discordant capacitance variations in response to discordant displacements of the first sensing mass and of the second sensing mass.

17. A system according to claim 16, wherein the first group of sensors and the second group of sensors are differential sensors.

18. A system according to claim 16, comprising a differential sensing interface and a routing stage, configured to invert the connection of one of the first group of sensors and the second group of sensors to inputs of the sensing interface between the first sensing mode and the second sensing mode.

19. A system according to claim 16, wherein the first sensing mass and the second sensing mass are constrained to the supporting structure to translate along the second axis.

20. A system according to claim 19, wherein the first group of sensors and the second group of sensors comprise first and second fixed sensing electrodes, respectively, that are anchored to the supporting structure, and first and second movable sensing electrodes each anchored to the first sensing mass and the second sensing mass, respectively, and interposed between the first fixed sensing electrodes and second fixed sensing electrodes, respectively.

21. A method, comprising:

oscillating a first sensing mass and a second sensing mass along a first axis in phase opposition;

maintaining the oscillating of the first sensing mass and the second sensing mass with a driving device;

generating sensing signals from a first group of sensors and a second group of sensors in response to displacements of the first sensing mass and of second sensing mass, respectively, with regard to second axis, perpendicular to the first axis;

combining the sensing signals in a first sensing mode and in a second sensing mode with processing components, the combining including;

amplifying during the first sensing mode, effects on the sensing signals of concordant displacements;

attenuating during the first sensing mode effects of discordant displacements of the first sensing mass and of the second sensing mass;

amplifying during the second sensing mode, effects on the sensing signals of discordant displacements; and

attenuating during the second sensing mode effects of concordant displacements of the first sensing mass and of the second sensing mass.

22. The method of claim 21 wherein the combining further includes:

adding during the first sensing mode effects on the sensing signals of displacements of the first sensing mass and of the second sensing mass caused by accelerations of the supporting structure along a sensing axis perpendicular to the first axis;

attenuating during the first sensing mode effects on the sensing signals of displacements of the first sensing mass and of the second sensing mass caused by rotations of the supporting structure about a third axis perpendicular to the first axis in combination with the oscillations according to the first axis;

adding in the second sensing mode effects on the sensing signals of displacements of the first sensing mass and of the second sensing mass caused by rotations of the supporting structure about the third axis in combination with the oscillations along the first axis; and

attenuating in the second sensing mode effects on the sensing signals of displacements of the first sensing mass and of the second sensing mass caused by accelerations of the supporting structure according to the sensing axis.

23. The method of claim 21, further comprising:

generating concordant capacitance variations in response to concordant displacements of the first sensing mass and of the second sensing mass; and

generating discordant capacitance variations in response to discordant displacements of the first sensing mass and of the second sensing mass, the first group of sensors and the second group of sensors being capacitive sensors.