FORCE SENSOR WITH REDUCED NOISE

• US 20110219875A1
• Filed: 03/11/2011
• Published: 09/15/2011
• Est. Priority Date: 03/15/2010
• Status: Active Grant

• Current Assignee: Commissariat a L'Energie Atomique (AES Corporation)
• Original Assignee: Energies Alternatives Commissariat A L'Energie Atomique et AUX
• Inventors: WALTHER, Arnaud, JOURDAN, Guillaume, ROBERT, Philippe
• Granted Patent: US 8,616,059 B2
• Time in Patent Office: Days
• US Class Current: 73/514.29
• CPC Class Codes: B81B 2201/0235 Accelerometers
• CPC Class Codes: B81B 2203/0163 Spring holders
• CPC Class Codes: B81B 2203/051 Translation according to an axis parallel to the substrate
• CPC Class Codes: B81B 3/0051 For defining the movement, i.e. structures that guide or limit the movement of an element mechanical arrangements for preventing or damping vibration or shock H01H3/60
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/123 by piezo-resistive elements, e.g. semiconductor strain gauges

Abstract

A MEMS or NEMS device for detecting a force following a given direction, comprising a support (4) and at least one seismic mass (2) capable of moving under the effect of the force to be measured in the direction of said force, and means (10) for detecting the movement of said seismic mass (2), said seismic mass being articulated relative to the support by at least one pivot link, and means capable of varying the distance between the axis (Z) of the pivot link and the center of gravity (G) of the exertion of the force on said seismic mass.

Claims

1. A microelectromechanical or nanoelectromechanical device for detecting a force following a given direction, comprising:

a support

at least one seismic mass capable of moving under the effect of the force to be measured in the direction of said force, said mass comprising at least first part and second part able to move relative to each other

a detector for detecting the movement of said seismic mass, said seismic mass being articulated relative to the support by at least one pivot link,

an actuator capable of making the distance between the axis of the pivot link and the center of gravity of the exertion of the force on said seismic mass vary at high frequency, said actuator being capable of moving the second part of the seismic mass relative to the first part of the seismic mass in a direction different from that of the force to be measured, called excitation axis.

2. The detection device according to claim 1, wherein the excitation frequency of the actuator is in the vicinity of several kHz.

3. The detection device according to claim 1, wherein the actuator is arranged between the first part and second part and is exerted on the second part.

4. The detection device according to claim 1, wherein the actuator is arranged between the support and the second part and is exerted on the second part via an intermediate seismic mass capable of moving only along the excitation axis.

5. The detection device according to claim 1, wherein the actuator is of the electrostatic, piezoelectric, or magnetic type.

6. The detection device according to claim 1, wherein the detector is of the capacitive, piezoelectric, magnetic, piezoresistive, frequency, or other type.

7. The detection device according to claim 6, wherein the detector comprises at least one piezoresistive gauge, and advantageously two piezoresistive gauges arranged on either side of the axis of the pivot link.

8. The detection device according to claim 7, wherein the second part of the seismic mass is capable of moving in a plane of the seismic mass, the suspension means being formed by at least one spring deforming in the plane.

9. The detection device according to claim 1, wherein the second part of the seismic mass has a movement outside the plane of the seismic mass, the suspension means being formed by at least one spring deforming out of plane.

10. The detection device according to claim 1, wherein the first part forms a frame inside which the second part is suspended.

11. The detection device according to claim 1, comprising two seismic masses each comprising a first and a second part connected to each other and able to move relative to each other, the first parts being rigidly connected by an arm, the pivot link being made on the arm, and the detector detecting the movement of said arm, the two second mobile parts moving in phase relative to each other.

12. The detection device according to claim 1, comprising a seismic mass having at least first and second parts able to move relative to each other, the pivot link being made on the first part, the actuator being arranged between the support and the second part and being exerted thereon via an intermediate seismic mass capable of moving only along the excitation axis, said two parts being positioned relative to each other so that the axis cutting the axis of the pivot link and passing through the center of gravity of the mass, in the absence of excitation, is perpendicular to the direction of the force to be detected.

13. The detection device according to claim 1, wherein the at least one seismic is suspended by a beam, the axis of the pivot link being substantially orthogonal to the device plane.

14. The detection device according to claim 13, wherein the mechanical link between the piezoresistive gauge(s) and the seismic mass is situated on or as close as possible to the plane containing the center of gravity and the axis of the pivot link.

15. The detection device according to claim 1, wherein the seismic mass is suspended by a torsion shaft whereof the axis is contained in the plane.

16. The detection device according to claim 1, comprising counter-reaction electrodes and/or electrodes for adjusting the resonance frequency.

17. An accelerometer formed by a microelectromechanical or nanoelec-tromechanical device for detecting an acceleration force following a given direction, comprising:

a support

at least one seismic mass capable of moving under the effect of the acceleration force to be measured in the direction of said acceleration force, said mass comprising at least first part and second part able to move relative to each other

a detector for detecting the movement of said seismic mass, said seismic mass being articulated relative to the support by at least one pivot link,

an actuator capable of making the distance between the axis of the pivot link and the center of gravity of the exertion of the acceleration force on said seismic mass vary at high frequency, said actuator being capable of moving the second part of the seismic mass relative to the first part of the seismic mass in a direction different from that of the acceleration force, called excitation axis.

18. The accelerometer according to claim 17, comprising electrodes for compensating quadrature bias on which a direct voltage and an alternating voltage are applied at a frequency that is twice the excitation frequency.

19. The accelerometer according to claim 17 being implemented under vacuum.