Underwater acoustic vector sensor using transverse-response free, shear mode, PMN-PT crystal

• US 7,066,026 B2
• Filed: 07/09/2004
• Issued: 06/27/2006
• Est. Priority Date: 07/11/2003
• Status: Expired due to Fees

• Current Assignee: Amphenol (Maryland), Inc. (Amphenol Corporation)
• Original Assignee: Meggitt (Maryland), Inc. (Amphenol Corporation)
• Inventors: Deng, Ken Kan
• Primary Examiner(s): KWOK, HELEN C
• Application Number:
  US10/887,347
• Publication Number:
  US 20050034519A1
• Time in Patent Office: 718 Days
• Field of Search: 735/143.4, 736/54, 736/49, 310/329, 310/360, 310/333
• US Class Current: 73/514.34
• CPC Class Codes: G01P 15/0915 of the shear mode type
• CPC Class Codes: G01P 15/18 in two or more dimensions
• CPC Class Codes: G01V 1/16 Receiving elements for seismic signals; Arrangements or adaptations of receiving elements
• CPC Class Codes: H10N 30/302 Sensors

Abstract

The present invention is directed to an acoustic vector sensor, also called particle velocity sensor. <111> direction poled, shear mode, relaxor single crystals are used as the sensing elements. In addition, these crystal plates are cut at a special orientation such that they provide zero or minimum responses in the transverse directions, but have a maximum piezoelectric response in sensing direction. The piezoelectric sensor contains a proof mass, a base, and an aforementioned relaxor crystal. Three of the sensors are mounted orthogonally with a rigid case, and they are designated to sense the acoustic particle velocity in three designated directions, say X, Y, and Z. To solve the adverse lateral constraint problem (also known as clamping effect) associated with the relaxor crystal; reduced bonding area between the proof mass and the relaxor crystal are introduced. This feature greatly reduced the percentage of the bonding area for the crystal; consequently the free-state piezoelectric properties of the relaxor crystals are preserved.

Claims

1. A piezoelectric sensor comprising

a proof mass;

a base; and

a piezoelectric crystal between the proof mass and the base, wherein bonding surfaces between the piezoelectric crystal and the proof mass and/or between the piezoelectric crystal and the base are castellated.

2. The sensor of claim 1, wherein the piezoelectric crystal is a shear mode (d₁₅) relaxor single crystal.

3. The sensor of claim 1, wherein the piezoelectric crystal is a PMN-PT crystal, poled along <

111> and

having a piezoelectric matrix d including coefficients d₁₅ and d₁₆, and wherein the piezoelectric crystal is rotated around its X axis by an angle

4. The sensor of claim 1, wherein the castellation comprises raised protrusions from a surface of the proof mass and/or a surface of the base that are in contact with the piezoelectric crystal.

5. An acoustic vector sensor comprising three piezoelectric sensors of claim 1.

6. The sensor of claim 5, wherein the piezoelectric crystal is a shear mode (d₁₅) relaxor single crystal.

7. The sensor of claim 5, wherein the piezoelectric crystal is a PMN-PT crystal, poled along <

111> and

having a piezoelectric matrix d including coefficients d₁₅ and d₁₆, and wherein the piezoelectric crystal is rotated around its X axis by an angle

8. The sensor of claim 5, wherein the castellation comprises raised protrusions from surfaces of the proof mass and of the base that are in contact with the piezoelectric crystal.

9. The sensor of claim 5, wherein the three piezoelectric sensors are mounted in a rigid housing.

10. The sensor of claim 9, wherein the housing is sealed and maintains neutral buoyancy in water.

11. The sensor of claim 9, wherein the housing is dimensioned to be smaller than or equal to one half wavelength of a highest frequency of interest.

12. The sensor of claim 5, wherein each of the three piezoelectric sensors senses acoustic energy from one of the three axial directions (X, Y, and Z).

13. The sensor of claim 5, wherein the three piezoelectric sensors are mounted orthogonally to each other.

14. A piezoelectric sensor comprising

a proof mass;

a base; and

a piezoelectric crystal between the proof mass and the base, wherein the piezoelectric crystal is a shear mode (d₁₅) relaxor single crystal.

15. The sensor of claim 14, wherein the piezoelectric crystal is a PMN-PT crystal, poled along <

111> and

having a piezoelectric matrix d including coefficients d₁₅ and d₁₆, and wherein the piezoelectric crystal is rotated around its X axis by an angle

16. An acoustic vector sensor comprising three piezoelectric sensors of claim 14.

17. The sensor of claim 16, wherein the piezoelectric crystal is a PMN-PT crystal, poled along <

111> and

having a piezoelectric matrix d including coefficients d₁₅ and d₁₆, and wherein the piezoelectric crystal is rotated around its X axis by an angle

18. The sensor of claim 16, wherein the three piezoelectric sensors are mounted in a rigid housing.

19. The sensor of claim 18, wherein the housing is sealed and maintains neutral buoyancy in water.

20. The sensor of claim 18, wherein the housing is dimensioned to be smaller than or equal to one half wavelength of a highest frequency of interest.

21. The sensor of claim 16, wherein each of the three piezoelectric sensors senses acoustic energy from one of the three axial directions (X, Y, and Z).

22. The sensor of claim 16, wherein the three piezoelectric sensors are mounted orthogonally to each other.

23. An acoustic vector sensor piezoelectric sensor comprising

a) a sealed and rigid housing that maintains neutral buoyancy in water;

and

b) three piezoelectric sensors orthogonally mounted inside the rigid housing, wherein each of the three piezoelectric sensors contains

i) a proof mass,

ii) a base, and

iii) a shear mode (d₁₅) relaxor single piezoelectric crystal between the proof mass and the base, wherein bonding surfaces between the piezoelectric crystal and the proof mass and/or between the crystal and the base are castellated.

24. The piezoelectric sensor comprising

a proof mass;

a base; and

a piezoelectric crystal between the proof mass and the base, wherein the piezoelectric crystal is a <

111>

direction poled, shear mode relaxor single crystal.

25. The sensor of claim 24, wherein the piezoelectric crystal has a piezoelectric matrix d including coefficients d₁₅ and d₁₆, and wherein the piezoelectric crystal is rotated around its X axis by an angle

26. The sensor of claim 24, wherein at least one of the proof mass and the base has raised protrusions that are in contact with the piezoelectric crystal.

27. An acoustic vector sensor comprising three piezoelectric sensors of claim 24.