Micromachined double tuning-fork gyrometer with detection in the plane of the machined wafer

• US 7,284,429 B2
• Filed: 08/31/2004
• Issued: 10/23/2007
• Est. Priority Date: 09/09/2003
• Status: Active Grant

• Current Assignee: Thales SA
• Original Assignee: Thales SA
• Inventors: Chaumet, Bernard, Rougeot, Claude, Leverrier, Bertrand
• Primary Examiner(s): Williams; Hezron
• Assistant Examiner(s): BELLAMY, TAMIKO D
• Application Number:
  US10/929,398
• Publication Number:
  US 20050050954A1
• Time in Patent Office: 1,148 Days
• Field of Search: 735/041.2, 735/041.5, 735/041.6, 310/329, 310/370
• US Class Current: 73/504.12
• CPC Class Codes: G01C 19/5747 each sensing mass being connected to a driving mass, e.g. driving frames

Abstract

The invention relates to a gyrometer based on a vibrating structure, produced by micromachining in a thin planar wafer. It comprises four moving assemblies placed at the vertices of a virtual rectangle, each moving assembly being coupled to two moving assemblies located at neighboring vertices via a coupling structure and comprising an inertial first moving element connected to the coupling structure and intended to vibrate in two orthogonal directions in the plane of the wafer, namely an excitation direction and a detection direction, and a second moving element intended to vibrate in the detection direction and connected, on one side, to the first moving element and, on the other side, to anchoring zones via linking means.

Claims

1. A gyrometer based on a planar vibrating structure, comprising:

four moving assemblies placed at the vertices of a virtual rectangle in order to allow a rotation measurement with minimal perturbations due to an excitation movement,

each moving assembly being coupled to two moving assemblies located at neighboring vertices via a coupling structure in order to allow transfer of mechanical vibration energy between them, each moving assembly including

a first inertial moving element connected to the coupling structure and intended to vibrate in two orthogonal directions in the plane of the vibrating structure, a first direction, called the excitation direction, and

a second direction, called the detection direction, a second moving element intended to vibrate in the detection direction without permitting movement of the second element in the excitation direction and connected, on one side, to the first moving element, and, on the other side, to anchoring zones via linking means which allow transmission to the second moving element of the vibration movement of the first moving element in the detection direction.

2. The gyrometer as claimed in claim 1, wherein the first moving element is a frame surrounding the second moving element called the detection mass.

3. The gyrometer as claimed in claim 2, wherein the frame is substantially rectangular.

4. The gyrometer as claimed in claim 2, wherein the detection mass is connected to the frame by at least two straight and elongate first flexure arms which have a high resistance to elongation in the detection direction and a low stiffness in the excitation direction, and the detection mass is connected to at least one anchoring zone by at least two second narrow and elongate flexure arms which have a high resistance to elongation in the excitation direction and a low stiffness in the detection direction.

5. The gyrometer as claimed in claim 1, wherein each moving assembly is connected to at least one anchoring zone located toward the outside of the vibrating structure comprising the four moving assemblies via at least one stiffness element.

6. The gyrometer as claimed in claim 1, wherein the sides of the rectangle are parallel to Ox and Oy respectively.

7. The gyrometer as claimed in claim 6, wherein the excitation direction of each first moving element is parallel to Ox.

8. The gyrometer as claimed in claim 7, wherein each first moving element is intended to vibrate in phase opposition with the first elements located at the neighboring vertices of the virtual rectangle and wherein each second moving element is intended to vibrate in phase opposition with the second elements located at the neighboring vertices of the virtual rectangle.

9. The gyrometer as claimed in claim 6, wherein an axis of symmetry A3 lies in the plane of the vibrating structure and along Oy, such that the excitation vibrations of the first moving elements of two moving assemblies that are located on one side of the axis A3 are symmetrical with respect to the excitation vibrations of the first moving elements of the two other moving assemblies tat are located on the other side of this axis A3.

10. The gyrometer as claimed in claim 6, wherein an axis of symmetry A4 lies in the plane of the vibrating structure and along Ox, such that the detection vibrations of the second moving elements of two moving assemblies that are located on one side of the axis A4 are symmetrical with respect to the detection vibrations of the second moving elements of the two other moving assemblies that are located on the other side of this axis A4.

11. The gyrometer as claimed in claim 6, which includes a pair of first stiffness elements can deform in directions parallel to Ox and Oy respectively, each first stiffness element connecting, parallel to Ox, two moving assemblies that are located at neighboring vertices of the virtual rectangle.

12. The gyrometer as claimed in claim 6, which includes a pair of second stiffness elements can deform in directions parallel to Ox and Oy respectively, each second stiffness element connecting, parallel to Oy, two moving assemblies that are located at neighboring vertices of the virtual rectangle.

13. The gyrometer as claimed in claim 6, wherein each moving assembly is connected to a first outer anchoring zone by a third stiffness element that can deform in directions parallel to Ox and Oy respectively, comprising a U-shaped arm which surrounds the outer side parallel to Oy of each moving assembly and which is connected to the moving assembly by short rigid links located at the ends of the U.

14. The gyrometer as claimed in claim 6, wherein each moving assembly is connected to a second outer anchoring zone by a fourth stiffness element that can deform in directions parallel to Ox and Oy respectively, which comprises an arm in the form of a flattened rectangle parallel to Ox and, on either side of the rectangle, a deformable link connecting the middle of each length of the flattened rectangle, on the one hand, to the second anchoring zone, and on the other hand, to the moving assembly.

15. The gyrometer as claimed in claim 1, wherein the rectangle is a square and wherein the diagonals of the square are parallel to Ox and Oy respectively.

16. The gyrometer as claimed in claim 15, wherein the moving assemblies are arranged so that the excitation direction is parallel to Ox in the case of two first elements located at the vertices of the diagonal along Ox and is parallel to Oy in the case of the two first elements located at the vertices of the diagonal along Oy.

17. The gyrometer as claimed in claim 15, wherein the moving assemblies are placed so that the excitation direction is parallel to Oy in the case of two first elements located at the vertices of the diagonal along Ox and is parallel to Ox in the case of the two first elements located at the vertices of the diagonal along Oy.

18. The gyrometer as claimed in claim 15, wherein each first moving element undergoing an excitation movement is intended to vibrate in phase opposition with the first moving element located at the opposite vertex of the square and wherein each second moving element undergoing a detection movement is intended vibrate in phase opposition with the second moving element located at the opposite vertex of the square.

19. The gyrometer as claimed in claim 15, which has an axis of symmetry A3 lying in the plane of the vibrating structure and oriented at ±

45°

with respect to Ox, such tat the excitation vibrations of the first moving elements of two moving assemblies that are located on one side of the axis A3 are symmetrical with respect to the excitation vibrations of the first moving elements of the two other moving assemblies located on the other side of this axis A3.

20. The gyrometer as claimed in claim 15, which has an axis of symmetry A4 lying in the plane of the vibrating structure and oriented at ±

45°

with respect to Ox, such that the detection vibrations of the second moving elements of two moving assemblies that are located on one side of the axis A4 are symmetrical with respect to the detection vibrations of the second moving elements of the two other moving assemblies that are located on the other side of this axis A4.

21. The gyrometer as claimed in claim 1, wherein the inertial first moving element and the second moving element coincide in the moving assembly I, the four moving elements being arranged at the vertices of a virtual rectangle, the sides of which are parallel to Ox and Oy respectively, each moving assembly being connected to the coupling structure that comprises stiffness elements that can deform in directions parallel to Ox end Oy respectively, each moving assembly I being connected to an anchoring zone 24 by a stiffness element 4 that can deform in a direction parallel to Ox and to an anchoring zone 25 by a stiffness element 5 that can deform in a direction parallel to Oy.