Accelerometer featuring fiber optic bragg grating sensor for providing multiplexed multi-axis acceleration sensing

• US 6,175,108 B1
• Filed: 01/30/1998
• Issued: 01/16/2001
• Est. Priority Date: 01/30/1998
• Status: Expired due to Term

• Current Assignee: Weatherford Technology Holdings, LLC (Weatherford International PLC)
• Original Assignee: Cidra Sarl (Nordic Cultural & Educational Foundation)
• Inventors: Maron, Robert J., Daigle, Guy A., Jones, Richard T.
• Primary Examiner(s): Lee, John R.
• Application Number:
  US09/016,258
• Time in Patent Office: 1,082 Days
• Field of Search: 250/231.1, 250/227.14, 250/227.11, 250/227.18, 735/140.1, 735/141.6, 735/141.7, 735/141.9, 735/142.4, 735/142.6, 735/142.7, 735/143.8, 735/142.1, 735/142.3, 735/143.6, 385/12, 385/13
• US Class Current: 250/227.14
• CPC Class Codes: G01P 15/093 by photoelectric pick-up
• CPC Class Codes: G01P 15/18 in two or more dimensions

Abstract

An accelerometer has a main body in combination with one or more Bragg grating sensors respectively arranged along one or more axes. The main body has a mass that responds to an acceleration, for providing a force having a component in one or more axes. The Bragg grating sensor means responds to the force, and further responds to an optical signal, for providing a Bragg grating sensor signal containing information about the acceleration respectively in one or more axes. The one or more axes may include orthogonal axes such as the X, Y and Z Euclidian axes. In one embodiment, the main body includes a proof mass and a pair of flexure disks, each having an inner ring, an outer ring, and radial splines connecting the inner ring and the outer ring. The proof mass is slidably arranged between the flexure disks. The Bragg grating means has an optical fiber and a Bragg grating sensor arranged therein. A first end of the Bragg grating sensor is fixedly coupled by a first ferrule to the proof mass. A second end of the Bragg grating sensor is fixedly coupled by a second ferrule to a housing of the accelerometer. In operation, the compression or stretching of a Bragg grating sensor causes a wavelength shift in the optical signal that contains information about the acceleration and that is sensed by a detector.

Claims

1. An accelerometer, comprising:

a main body having a housing with a wall, and having a seismic mass means arranged between a diaphragm means and the wall of the housing, the seismic mass means and the diaphragm means responding to an acceleration, for providing a force in at least two orthogonal axes; and

Bragg grating sensors including an optical fiber having two Bragg gratings disposed therein, a first Bragg grating being disposed in the optical fiber arranged on the diaphragm means, a second Bragg grating being disposed on the optical fiber arranged between the seismic mass means and the wall of the housing, each Bragg grating responsive to the force, and further responsive to an optical signal, for providing respective Bragg grating sensor signals containing information about the acceleration in the at least two orthogonal axes.

2. An accelerometer according to claim 1, wherein the seismic mass means is a mass fixedly arranged on the diaphragm means.

3. An accelerometer according to claim 2,

wherein the diaphragm means has a diaphragm; and

wherein the seismic mass means is arranged at a center of the diaphragm.

4. An accelerometer according to claim 1, wherein the diaphragm means has a diaphragm that is clamped along edges of the wall of the housing.

5. An accelerometer according to claim 1, wherein the first Bragg grating is glued or epoxied onto the diaphragm means.

6. An accelerometer according to claim 1, wherein the optical fiber is connected by ferrules to the seismic mass means and the wall of the housing.

7. An accelerometer according to claim 1, wherein the accelerometer has a mechanical stop arranged between the seismic mass means and the wall of the housing.

8. An accelerometer according to claim 1, wherein the diaphragm means has a diaphragm that is clamped along a center support connected to the wall of the housing.

9. An accelerometer according to claim 8, wherein the seismic mass means includes two masses, each fixedly arranged on a respective edge of the diaphragm means.

10. An accelerometer according to claim 9, wherein the accelerometer has a respective mechanical stop arranged between each of the two masses and the wall of the housing.

11. An accelerometer according to claim 1, wherein the diaphragm means includes two diaphragms and the seismic mass means is arranged therebetween.

12. An accelerometer according to claim 11, wherein the accelerometer has a respective mechanical stop arranged on each side of the two diaphragms and coupled to the wall of the housing.