Three-mass coupled oscillation technique for mechanically robust micromachined gyroscopes

• US 8,955,381 B2
• Filed: 09/13/2012
• Issued: 02/17/2015
• Est. Priority Date: 09/13/2011
• Status: Active Grant

• Current Assignee: IMEC International
• Original Assignee: IMEC International
• Inventors: Erismis, Mehmet Akif
• Primary Examiner(s): CHAPMAN JR, JOHN E
• Application Number:
  US13/613,770
• Publication Number:
  US 20130061673A1
• Time in Patent Office: 887 Days
• Field of Search: 735/041.2, 735/041.4
• US Class Current: 73/504.12
• CPC Class Codes: G01C 19/5733 Structural details or topology
• CPC Class Codes: Y10T 29/49 Method of mechanical manufacture

Abstract

A micromachined gyroscope is disclosed comprising a substrate, three masses m₁, m₂, and m₃, configured to oscillate along a first direction x or y, whereby the first mass m₁ is mechanically coupled to the substrate, the second mass m₂ is mechanically coupled to the first mass m₁ and to substrate, and the third mass m₃ is mechanically coupled to the second mass m₂, whereby the weight and the spring constants k₁, k₂, k₃ of the respective masses m₁, m₂, and m₃ and mechanical couplings k₁₂, k₂₃ are selected, such that, during operation mass m₂ oscillates at a frequency substantially above the resonance frequencies of mass m₁ and mass m₃. The resonance frequency of mass m₂ may be at least 2 times, or even 2.5 times, higher than the resonance frequency of mass m₁ or m₃.

Claims

1. A micromachined gyroscope comprising a three-mass configuration that includes a substrate and three masses configured to oscillate in a first direction, wherein:

a first mass having a first weight m₁ is mechanically coupled to the substrate;

a second mass having a second weight m₂ is mechanically coupled to the first mass and to the substrate; and

a third mass having a third weight m₃ is mechanically coupled to the second mass, wherein the following relationship exist;

[(k₂+k₁₂+k₂₃)/m₂]>

>

([(k₁+k₁₂)/m₁]˜

[(k₂₃)/m_3])

wherein k₁ is a spring constant of a mechanical connection between the first mass and the substrate, k₂ is a spring constant of a mechanical connection between the second mass and the third substrate, k₁₂ is a spring constant of a mechanical connection between the first mass and the second mass, and k₂₃ is a spring constant of a mechanical connection between the second mass and the third mass.

2. The micromachined gyroscope of claim 1, wherein the third mass is mechanically coupled to the substrate, and wherein the following relationship exists:

[(k₂+k₁₂+k₂₃)/m₂]>

>

[(k₁+k₁₂)/m₁]˜

[k₃+k₂₃)/m₃]

wherein k₃ is a spring constant of a mechanical connection between the third mass and the substrate.

3. The micromachined gyroscope of claim 1, wherein the three masses are driving masses, and further comprising driving means to drive the first mass.

4. The micromachined gyroscope of claim 3, wherein the driving means are parallel plate electrostatic actuators.

5. The micromachined gyroscope claim 1, wherein the three masses are sensing masses configured to move when the micromachined gyroscope is rotated.

6. The micromachined gyroscope of claim 1, further comprising a duplicate of the three-mass configuration, wherein the duplicate is configured to oscillate in the first direction but in an opposite phase of the three-mass configuration.

7. The micromachined gyroscope of claim 1 wherein, the three masses are configured to oscillate linearly.

8. A method for designing a micromachined gyroscope comprising:

selecting a first mass having a first weight m₁;

selecting a second mass having a second weight m₂;

selecting a third mass having a third weight m₃;

selecting a first spring constant k₁ for a mechanical connection between the first mass and a substrate;

selecting a second spring constant k₂ for a mechanical connection between the second mass and the substrate;

selecting a third spring constant k₃ for a mechanical connection between the third mass and the substrate;

selecting a fourth spring constant k₁₂ for a mechanical connection between the first mass and the second mass; and

selecting a fifth spring constant k₂₃ for a mechanical connection between the second mass and the third mass, wherein;

[(k₁+k₁₂)/m₁]˜

[k₃+k₂₃)/m₃];

and wherein, during operation of the micromachined gyroscope;

[(k₂+k₁₂+k₂₃)/m₂]>

>

[(k₁+k₁₂)/m₁]>

[k₃+k₂₃)/m₃].

9. A method according to claim 8, further comprising:

selecting a mechanical amplification between a movement of the first mass and a movement of the third mass; and

dimensioning the second spring constant k₂ in view of the mechanical amplification.