Planar mechanical resonator sensitive along an axis perpendicular to its plane

• US 6,889,550 B2
• Filed: 01/29/2002
• Issued: 05/10/2005
• Est. Priority Date: 02/23/2001
• Status: Expired due to Fees

• Current Assignee: Sagem SA (Safran SA)
• Original Assignee: Sagem SA (Safran SA)
• Inventors: Beitia, José
• Primary Examiner(s): KWOK, HELEN C
• Application Number:
  US10/468,217
• Publication Number:
  US 20040112134A1
• Time in Patent Office: 1,197 Days
• Field of Search: 735/040.2, 735/040.4, 735/041.2, 735/041.3, 735/041.4, 735/041.5
• US Class Current: 73/504.12
• CPC Class Codes: G01C 19/5684 the devices involving a micromechanical structure

Abstract

The invention concerns a mechanical resonator with a planar monolithic vibrating structure extending along a closed contour whereof the axis of sensitivity is substantially perpendicular to the plane of said structure. The invention is characterised in that the planar structure (1) is a regular convex polygon with 4k vertices (3) (k being the order of the vibrational mode implemented when the resonator is vibrated) and is suspended to a fixed base (4, 5) via n suspension arms (2) with substantially radial extension arranged substantially symmetrically.

Claims

1. A mechanical resonator with a plane monolithic vibrating structure extending along a closed contour whose sensitivity axis is substantially perpendicular to the plane of said structure,

wherein the plane structure is a convex regular polygonal with 4k vertices, where k is the order of the vibratory mode implemented when the resonator is set vibrating and k≧

2, and is suspended from a fixed mount by way of n suspension arms of substantially radial extension which are arranged substantially symmetrically.

2. The mechanical resonator as claimed in claim 1, wherein the convex regular polygonal vibrating structure with 4k vertices possesses identical patterns which repeat with angular intervals of π

/2k, whereby said polygonal vibrating structure exhibits and isotropy of geometry (Δ

f_g=0, Δ

α

_g=0).

3. The mechanical resonator as claimed in claim 1, wherein, for a vibratory mode of order 2 (k=2), the plane vibrating structure is of octagonal shape and is made of a crystalline material with trigonal structure, with a cut made in the X, Y plane, whereby the vibrating structure exhibits an isotropy of material (Δ

f_m=0, Δ

α

_m=0) for order 2.

4. The mechanical resonator as claimed in claim 3, wherein the octagonal vibrating structure is made of quartz.

5. The mechanical resonator as claimed in claim 1, wherein, for a vibratory mode of order 3 (k=3), the plane vibrating structure is of dodecagonal shape and is made of a crystalline material with cubic structure, with a cut made in a plane containing the X axis, or the Y axis, or the Z axis, whereby the vibrating structure exhibits and isotropy of material (Δ

f_m=0, Δ

α

_m=0) for order 3.

6. The mechanical resonator as claimed in claim 5, wherein the dodecagonal vibrating structure is made of silicon.

7. The mechanical resonator as claimed in claim 1, wherein the suspension arms are n=4k in number and are angularly spaced by an angular interval of π

/2k, whereby the vibrating structure exhibits an isotropy of suspension (Δ

f_s0, Δ

α

_s=0).

8. The mechanical resonator as claimed in claim 2, wherein the polygonal vibrating structure simultaneously exhibits isotropies of geometry (Δ

f_g=0, Δ

α

_g=0) and of material (Δ

f_m=0, Δ

α

_m=0) and of suspension (Δ

f_s=0, Δ

α

_s=0), in terms of frequency and coupling, whereby it is able to operate in gyrometric mode or in gyroscopic mode.

9. The mechanical resonator as claimed in claim 1, wherein the polygonal vibrating structure with 4k vertices is made of a crystalline material with non trigonal structure of k=2 or non cubic structure for k=3, and therefore exhibits basically an anisotropy of material (Δ

f_m≠

0, Δ

α

_m≠

0), and wherein said polygonal vibrating structure is then devised so as furthermore to exhibit at least one localized modification of geometry and/or the suspension arms exhibits at least one localized modification, so that said polygonal vibrating structure exhibits and anisotropy of geometry (Δ

f_g≠

0, Δ

α

_g≠

0) and/or an anisotropy of suspension (Δ

f_s≠

0, Δ

α

_s≠

0), respectively able to compensate for the anisotropy of material, whereby said polygonal vibrating structure exhibits an isotropy in terms of frequency (Δ

f=0) and coupling (Δ

α

=0) and the resonator is able to operate in gyrometric mode or in gyroscopic mode.

10. The mechanical resonator as claimed in claim 1, wherein the suspension arms are n<

4k in number and are angularly spaced by an angular interval of 2π

/n, with n chosen such that n≦

k−

2 or n≧

k+2 with n≠

pk (p integer), the polygonal vibrating structure therefore exhibiting basically an anisotropy of suspension (Δ

f_s≠

0, Δ

α

_s≠

0) and wherein said polygonal vibrating structure is then devised so as to furthermore exhibit localized defects of geometry which are angularly offset by an angular value of π

/k and are able to cause a defect of mass of order 2k which engenders and anisotropy in terms of geometry (Δ

f_g≠

0, Δ

α

_g≠

0) able to compensate of the anisotropy of suspension due to the insufficient number of suspension arms, whereby said polygonal vibrating structure exhibits and isotropy in terms of frequency (Δ

f=0) and coupling (Δ

α

=0) and the resonator is able to operate in gyrometric mode or in gyroscopic mode.

11. The mechanical resonator as claimed in claim 10, herein the localized defects of geometry are situated at least in the vicinity of where the suspension arms are linked to the vibrating structure.

12. The mechanical resonator as claimed in claim 2, wherein the vibrating structure exhibits at least one anisotropy of geometry (Δ

f_g≠

0, Δ

α

_g≠

0), or of material (Δ

f_m≠

0, Δ

α

_m≠

0), or of suspension (Δ

f_s≠

0, Δ

α

_s≠

0) whereby said vibrating structure is able to operate only in gyrometric mode.

13. The mechanical resonator as claimed in claim 1, characterized in that the mount surrounds the plane vibrating structure and in that the suspension arms are outside the vibrating structure.

14. The mechanical resonator as claimed in claim 1, wherein the mount is a central hub substantially concentric with the vibrating structure and wherein the suspension arms are inside the vibrating structure.

15. The mechanical resonator as claimed in claim 13, further comprising resonating beams which are carried by a central hub substantially concentric with the vibrating structure with closed contour and which radiate around said central hub substantially in the plane of the vibrating structure with closed contour, whereby the mechanical resonator has the resonating beams and the vibrating structure situated substantially in the same plane and is able to detect the three components Ω

x, Ω

y and Ω

z of a rate of rotation Ω

imparted to the mount, the components Ω

x and Ω

y being detected by the beams and the component Ω

z being detected by the vibrating structure with closed contour and whereby the mechanical resonator is able to operate in gyrometric mode or in gyroscopic mode on the three axes.

16. The mechanical resonator as claimed in claim 14, further comprising resonating beams which are carried by a central hub substantially concentric with the vibrating structure with closed contour and which radiate around said central hub substantially in the plane of the vibrating structure with closed contour, whereby the mechanical resonator has the resonating beams and the vibrating structure situated substantially in the same plane and is able to detect the three components Ω

x, Ω

y, and Ω

z of a rate of rotation Ω

imparted to the mount, the components Ω

x and Ω

y being detected by the resonating beams and the component Ω

z being detected by the vibrating structure with closed contour and whereby the mechanical resonator is able to operate in gyrometric mode or in gyroscopic mode on the three axes.

17. The use of a plane mechanical resonator sensitive along the transverse axis to operation in gyroscopic mode as claimed in claim 11, within a plane monolithic gyro-accelerometric inertial sensor able to provide the information Ω

x, Ω

y, Ω

z and γ

_x, γ

_y, γ

_z.