Accelerometers

Patent metadata

Field	Value
Publication number	US-2016356806-A1
Application number	US-201515118995-A
Country	US
Kind code	A1
Filing date	Feb 16, 2015
Priority date	Feb 19, 2014
Publication date	Dec 8, 2016
Grant date	—

Abstract

A sensing structure for an accelerometer includes a support and a proof mass mounted to the support by flexible legs for in-plane movement in response to an applied acceleration along a sensing direction. The proof mass includes a plurality of moveable electrode fingers extending substantially perpendicular to the sensing direction and spaced apart in the sensing direction. The structure also includes at least one pair of fixed capacitor electrodes comprising first and second sets of fixed electrode fingers extending substantially perpendicular to the sensing direction and spaced apart in the sensing direction; the first set of fixed electrode fingers arranged to interdigitate with the moveable electrode fingers with a first offset in one direction from a median line therebetween, and the second set of fixed electrode fingers arranged to interdigitate with the moveable electrode fingers with a second offset in the opposite direction from a median line therebetween.

First claim

1 . A sensing structure for an accelerometer, comprising:
a support and a proof mass mounted to the support by flexible legs for in-plane movement in response to an applied acceleration along a sensing direction; the proof mass comprising a plurality of moveable electrode fingers extending substantially perpendicular to the sensing direction and spaced apart in the sensing direction; and at least one pair of fixed capacitor electrodes comprising first and second sets of fixed electrode fingers extending substantially perpendicular to the sensing direction and spaced apart in the sensing direction; the first set of fixed electrode fingers arranged to interdigitate with the moveable electrode fingers with a first offset in one direction from a median line therebetween, and the second set of fixed electrode fingers arranged to interdigitate with the moveable electrode fingers with a second offset in the opposite direction from a median line therebetween; wherein the proof mass takes the form of an outer frame surrounding the at least one pair of fixed capacitor electrodes, the flexible legs extending laterally inwardly from the proof mass to a central anchor having a position along the sensing direction that is centred with respect to the pair(s) of fixed capacitor electrodes.

2 . A sensing structure according to claim 1 , comprising at least two pairs of fixed capacitor electrodes.

3 . A sensing structure according to claim 2 , comprising an even number of further pairs of fixed capacitor electrodes.

4 . A sensing structure according to claim 1 , wherein the first and second sets of fixed electrode fingers of each pair are anchored to the support at a central position in line with the central anchor of the proof mass.

5 . A sensing structure according to claim 1 , comprising a shared electrical connection for the first and second sets of fixed electrode fingers of each pair, arranged in line with a central electrical connection for the proof mass.

6 . A sensing structure according to claim 1 , wherein the proof mass is connected to the central anchor by two or more separated pairs of flexible legs.

7 . A sensing structure according to claim 1 , wherein the proof mass is connected to the central anchor by a plurality of flexible support legs having a serpentine form.

8 . A sensing structure according to claim 9 , wherein each support leg comprises at least a first generally straight section, a second generally straight section, and an end section of generally U-shaped form interconnecting the first and second generally straight sections, wherein the thickness of the end section is greater than the thickness of a central part of both of the first and second generally straight sections.

9 . A sensing structure according to claim 1 , wherein the sensing structure is a microelectromechanical system (MEMS).

10 . A sensing structure according to claim 1 , wherein the support is made of glass.

11 . An accelerometer comprising a sensing structure according to claim 1 .

12 . An accelerometer according to claim 11 , the sensing structure comprising two pairs of fixed capacitor electrodes with a first and second upper set of fixed electrode fingers above the central anchor and a first and second lower set of fixed electrode fingers below the central anchor arranged to have symmetrical offsets, the first upper set of fixed electrode fingers being driven in phase with the first lower set of fixed electrode fingers and the second upper set of fixed electrode fingers being driven in phase with the second lower set of fixed electrode fingers.

13 . An accelerometer according to claim 11 , the sensing structure comprising two pairs of fixed capacitor electrodes with a first and second upper set of fixed electrode fingers above the central anchor and a first and second lower set of fixed electrode fingers below the central anchor arranged to have opposite offsets, the first upper set of fixed electrode fingers being driven in phase with the second lower set of fixed electrode fingers and the second upper set of fixed electrode fingers being driven in phase with the first lower set of fixed electrode fingers.

14 . An accelerometer according to claim 11 , wherein open loop electronics are arranged to drive the first and second sets of fixed electrode fingers of each pair in anti-phase.

15 . An accelerometer according to claim 11 , wherein closed loop electronics are arranged to drive the first and second sets of fixed electrode fingers of each pair in anti-phase.

Assignees

• Atlantic Inertial Systems Ltd

Inventors

• Malvern Alan Richard
• Harish Kiran

Classifications

• G01P2015/0814

  for translational movement of the mass, e.g. shuttle type · CPC title

• G01P15/125 Primary

  by capacitive pick-up · CPC title

• G01P1/006

  used for thermal compensation · CPC title

• G01P15/0802

  Details · CPC title