Micromachined inertial sensor for measuring rotational movements

• US 20040250620A1
• Filed: 06/04/2004
• Published: 12/16/2004
• Est. Priority Date: 12/20/2001
• Status: Active Grant

• Current Assignee: Thales SA
• Original Assignee: Thales SA
• Inventors: Nicu, Liviu, Inglese, Jerome, Rougeot, Claude, Leverrier, Bertrand, Lefort, Pierre-Olivier
• Granted Patent: US 7,210,347 B2
• Time in Patent Office: Days
• US Class Current: 73/504.12
• CPC Class Codes: G01C 19/574 the devices having two sensing masses in anti-phase motion

Abstract

The invention relates to gyroscopes having a vibrating structure that is micromachined in a silicon substrate. A novel vibrating structure is described, which has two moving masses 14 and 14′, connected by a vibration energy coupling structure (transverse arms 26, 26′, longitudinal arms 22, 22′, and a short transverse link 24 between the longitudinal links 22, 22′). The moving masses are also suspended from U-shaped flexure arms (13), having one branch end connected to the mass and another end connected to a fixed anchoring point 18. The flexure arms are not inserted between the coupling structure and the mass, but are independent of the coupling structure. The masses are excited so as to vibrate in their plane by electrostatic forces applied by interdigitated combs 11. The Coriolis forces make them vibrate perpendicular to the plane, and this vibration is detected by electrodes forming part of the moving masses.

Claims

1. A micromachined gyroscope having a plane moving structure anchored to a fixed substrate, the moving structure being symmetrical about a first axis, lying in this plane comprising:

two moving masses that are attached to flexure arms, the stiffness of which defines the main resonant frequency of the masses;

a structure for exciting the vibration of each mass in the plane of the structure;

a structure for detecting a vibration of the masses transverse to the plane; and

a mechanical coupling structure for connecting the masses together, ensuring that mechanical vibration energy is transferred from one mass to the other;

wherein the flexure arms connected to a moving mass are connected also to a fixed anchoring point, the inter-mass coupling structure being connected directly to the moving masses independently of the flexure arms and this coupling structure having a stiffness that is appreciably different from the stiffness of the flexure arms so that the main resonant frequency of the masses depends only slightly on the stiffness of the coupling structure.

2. The gyroscope as claimed in claim 1, wherein the coupling structure is attached to the moving mass at only two points that lie along an axis of longitudinal symmetry of the moving mass parallel to the sensitive axis.

3. The gyroscope as claimed in claim 1, wherein the flexure arms are each folded in the form of a U, the end of one branch of the U being attached to the moving mass and the end of the other branch being connected to said fixed anchoring point.

4. The gyroscope as claimed in claim 1, wherein said gyroscope includes two interdigitated excitation combs for setting each mass into vibration in the plane by electrostatic forces, and two interdigitated detection combs for detecting and monitoring this vibration.

5. The gyroscope as claimed in claim 1, wherein the flexure arms are placed symmetrically with respect to a second axis which is parallel to the sensitive axis and constitutes an axis of symmetry of the moving mass.

6. The micromachined gyroscope as claimed in claim 5, wherein each mass is connected to four U-shaped flexure arms, a combination of the mass and of the four flexure arms having a symmetrical configuration with respect to a third axis perpendicular to the first axis.

7. The gyroscope as claimed in claim 6, wherein each moving mass is connected via its flexure arms to a respective anchoring point located at a center of symmetry of the moving mass, at the intersection of the second and third axes.

8. The gyroscope as claimed in claim 6, wherein each mass is connected via two flexure arms to a first anchoring point and via two other flexure arms to a second anchoring point symmetrical with the first with respect to the third axis, the two anchoring points being located on either side of the moving mass.

9. The gyroscope as claimed in claim 6, wherein each moving mass is connected via four flexure arms to four anchoring points arranged in a symmetrical configuration with respect to a center of gravity of the moving mass.

10. The gyroscope as claimed in claim 1 wherein the coupling structure connecting the two moving masses has at least two longitudinal links extending on either side of the sensitive axis, parallel to the latter, between the moving masses, at least one transverse link connecting the two longitudinal links, and at least two transverse arms connecting each moving mass to a respective longitudinal link, the latter two transverse arms being located on either side of the moving mass and being connected to the moving mass.

11. The gyroscope as claimed in claim 10, wherein the transverse link connecting the two longitudinal links is placed along an axis of symmetry, perpendicular to the sensitive axis, of the moving masses.

12. The gyroscope as claimed in claim 10, wherein the coupling structure comprises another transverse link connecting the two longitudinal links, the two transverse links being separated from each other and being placed symmetrically with respect to an axis of symmetry, perpendicular to the first axis, of the moving masses.

13. The gyroscope as claimed in claim 10, wherein the coupling structure includes, for each moving mass, two longitudinal arms parallel to the first axis, which arms are located on either side of the moving mass and connect a respective transverse arm to the moving mass.

14. The gyroscope as claimed in claim 13, wherein the two longitudinal arms are connected to the moving mass on either side of the latter at two points located on an axis of symmetry of the moving mass, parallel to the first axis.

15. The gyroscope as claimed in claim 10, wherein the coupling structure is connected to at least one additional respective anchoring point associated with each moving mass, this anchoring point being located on the other side of the moving mass relative to the first axis, the transverse arms (26) being connected to this anchoring point via other respective longitudinal links.

16. The gyroscope as claimed in claim 9, each moving mass is connected via four flexure arms to four anchoring points arranged in a symmetrical configuration with respect to a center of gravity of the moving mass wherein the longitudinal arms each pass between two respective anchoring points taken from the four anchoring points.

17. The gyroscope as claimed in claim 2, wherein the flexure arms are each folded in the form of a U, the end of one branch of the U being attached to the moving mass and the end of the other branch being connected to said fixed anchoring point.

18. The gyroscope as claimed in claim 2, wherein said gyroscope includes two interdigitated excitation combs for setting each mass into vibration in the plane by electrostatic forces, and two interdigitated detection combs for detecting and monitoring this vibration.

19. The gyroscope as claimed in claim 3, wherein said gyroscope includes two interdigitated excitation combs for setting each mass into vibration in the plane by electrostatic forces, and two interdigitated detection combs for detecting and monitoring this vibration.

20. The gyroscope as claimed in claim 2, wherein the flexure arms are placed symmetrically with respect to a second axis which is parallel to the sensitive axis and constitutes an axis of symmetry of the moving mass.

21. The gyroscope as claimed in claim 3, wherein the flexure arms are placed symmetrically with respect to a second axis which is parallel to the sensitive axis and constitutes an axis of symmetry of the moving mass.

22. The gyroscope as claimed in claim 4, wherein the flexure arms are placed symmetrically with respect to a second axis which is parallel to the sensitive axis and constitutes an axis of symmetry of the moving mass.

23. The gyroscope as claimed in claim 11, wherein the coupling structure comprises another transverse link connecting the two longitudinal links, the two transverse links being separated from each other and being placed symmetrically with respect to an axis of symmetry, perpendicular to the sensitive axis, of the moving masses.