Excitation in micromechanical devices

• US 7,430,908 B2
• Filed: 10/06/2006
• Issued: 10/07/2008
• Est. Priority Date: 11/04/2005
• Status: Expired due to Fees

• Current Assignee: Infineon Technologies AG
• Original Assignee: Infineon Technologies Sensonor AS (Infineon Technologies AG)
• Inventors: Westby, Esklid
• Primary Examiner(s): Kwok; Helen C.
• Application Number:
  US11/539,182
• Publication Number:
  US 20070111363A1
• Time in Patent Office: 732 Days
• Field of Search: 735/040.2, 735/040.4, 735/041.2, 735/041.4, 735/041.5, 735/141.5, 735/141.6, 735/142.9
• US Class Current: 73/504.04
• CPC Class Codes: B81B 2201/0271 Resonators; ultrasonic resonators
• CPC Class Codes: B81B 2203/0109 Bridges
• CPC Class Codes: B81B 3/0067 Mechanical properties
• CPC Class Codes: G01C 19/5712 the devices involving a micromechanical structure

Abstract

A resonant structure for a micromechanical device includes a beam and at least one mass attached to the beam. The resonant structure is arranged to have a predominantly rotational excitation mode and an excitation plane in which motion of the excited resonant structure predominantly takes place, the at least one mass including a geometry such that none of the principal axes of the rotational inertia tensor of the resonant structure are normal to the excitation plane.

Claims

1. A micromechanical device comprising:

a resonant structure comprising a beam; and

at least one mass attached to the beam; and

an excitation component configured to excite motion of the resonant structure;

wherein the resonant structure is configured to have a predominantly rotational excitation mode defined in an excitation plane in response to the resonant structure being excited, and the at least one mass includes a suitable geometry that prevents any principal axis of a rotational inertia tensor of the resonant structure from being normal to the excitation plane.

2. The device according to claim 1, wherein the beam comprises a rectangular cross-section normal to the excitation plane.

3. The device according to claim 1, wherein the at least one mass is asymmetric about an axis through a center of the beam and parallel to a length of the beam.

4. The device according to claim 1, wherein the at least one mass comprises a two-fold rotational symmetry about an axis through a center of the beam and parallel to a length of the beam but no minor symmetry about the same axis.

5. The device according to claim 1, wherein the resonant structure comprises a sensing element.

6. The device according to claim 1, wherein the micromechanical device comprises a sensing device and the excitation component is configured to excite motion of the sensing element in a direction normal to the excitation plane, and the device further comprises a detection component configured to detect a motion in a direction normal to the excitation plane and that is not caused by the excitation component.

7. The device according to claim 1, wherein the resonant structure is arranged to be excitable to a predominantly rotational excitation mode.

8. The device according to claim 1, wherein the micromechanical device comprises a power generation device and the resonant structure is arranged to be excitable to a predominantly rotational excitation mode, the resonant structure being fixed to a wheel such that the rotation axis of the excited resonant structure is substantially perpendicular to the rotation axis of the wheel, and the device further comprises a power extraction component configured to generate power via converting Coriolis motion of the excited resonant structure.

9. The device according to claim 1, wherein the excitation component is configured to electrostatically excite motion of the resonant structure.

11. The device of claim 1, wherein the resonant structure is configured with a suitable geometry of the at least one mass so as to prevent any principal axis of a rotational inertia tensor of the resonant structure from being normal to the excitation plane in response to the resonant structure being excited without requiring a movement of any mass associated with the resonant structure or any modification of a center of mass of the resonant structure.

13. The device of claim 1, wherein at least one mass of the resonant structure includes an irregular geometry with at least one side of the mass comprising two surfaces that are non-planar with each other such that a stepped transition exists between the two surfaces.

10. A method of exciting a resonant structure in an excitation plane in a micromechanical device, the method comprising:

providing a resonant structure including at least one mass with a suitable geometry that prevents any principal axis of a rotational inertia tensor of the resonant structure from being normal to the excitation plane; and

exciting motion of the resonant structure in a direction normal to the excitation plane.

12. The method of claim 10, wherein the resonant structure is configured with a suitable geometry of the at least one mass so as to prevent any principal axis of a rotational inertia tensor of the resonant structure from being normal to the excitation plane in response to the resonant structure being excited without requiring a movement of any mass associated with the resonant structure or any modification of a center of mass of the resonant structure.

14. The method of claim 10, wherein at least one mass of the resonant structure includes an irregular geometry with at least one side of the mass comprising two surfaces that are non-planar with each other such that a stepped transition exists between the two surfaces.