Piezoelectric rotational accelerometer

• US 6,397,677 B1
• Filed: 06/06/2000
• Issued: 06/04/2002
• Est. Priority Date: 06/06/2000
• Status: Expired due to Term

• Current Assignee: Kistler Instrument Corp (Kistler Holding AG)
• Original Assignee: Kistler Instrument Corp (Kistler Holding AG)
• Inventors: Kinsley, Norton, Insalaco, Michael D.
• Primary Examiner(s): KWOK, HELEN C
• Application Number:
  US09/587,974
• Time in Patent Office: 728 Days
• Field of Search: 735/143.4, 734/93, 735/143.6, 735/143.7, 738/620.43, 738/626.38, 736/54, 736/51, 310/329, 310/333
• US Class Current: 73/514.34
• CPC Class Codes: G01P 15/0888 for indicating angular acceleration
• CPC Class Codes: G01P 15/0915 of the shear mode type
• CPC Class Codes: G01P 15/18 in two or more dimensions

Abstract

A rotational accelerometer using piezoelectric material, preferably quartz, in a shear orientation. Piezoplates and conducting seismic masses, each having bores therethrough, are bolted to posts that are symmetrically mounted to a body in such a manner that the bolt passes through the piezoplates but does not make contact. The accelerometer can be assembled as a single-axis accelerometer by mounting a pair of posts symmetrically about the body along the measured axis; additionally, the accelerometer may be assembled as a double or triple axis accelerometer by symmetrically mounting additional pairs of posts to the body. The total weight of the seismic masses and the crystals of the shear-type accelerometer halves should be equal. The invention sets forth a novel rotational accelerometer that reduces or eliminates the need for signal-processing electronics.

Claims

1. A rotational accelerometer comprising:

first and second spaced-apart linear accelerometers each having first and second piezoplates and corresponding first and second seismic mass clamped to a corresponding post;

the piezoplates of each linear accelerometer having parallel first axes of sensitivity and being electrically connected to be sensitive to linear acceleration along the parallel axes;

each of the post being connected to a body so that the first axes of both linear accelerometers are parallel; and

the polarity of the linear accelerometers being opposed and electrically connected to be sensitive in combination to rotational acceleration about a second axis perpendicular to the first axes.

2. The accelerometer of claim 1, wherein the posts of the first and second linear accelerometers are substantially collinear and extend substantially orthogonally from the body.

3. The accelerometer of claim 1, wherein

the post, the piezoplates, and the seismic masses of the first linear accelerometer each have a first bore therein;

the post, the piezoplates, and the seismic masses of the second linear accelerometer each have a second bore therein;

a first metal bolt extending through each of the first bores and clamping each of the piezoplates and seismic masses to the post, the first bolt contacting neither the piezoplates nor the post; and

a second metal bolt passing through each of the second bores and clamping each of the piezoplates and seismic masses to the post, the second bolt contacting neither the piezoplates nor the post.

4. The accelerometer of claim 3, further comprising:

an electrical connection between the first bolt and a first electric terminal;

an electrical connection between the second bolt and the first electric terminal; and

an electrical connection between the body and a second electrical terminal, such that an electrical instrument can read a signal from between the first and second electrical terminals.

5. The accelerometer according to claim 3, wherein each bolt has a smaller diameter than diameter of the bores on the post so as to create a non-contact annulus therebetween.

6. The accelerometer according to claim 1, wherein each piezoplate is a shear type quartz piezoplate.

7. The accelerometer according to claim 1, wherein the piezoplates have equal dimensions.

8. The accelerometer according to claim 1, wherein the posts and the body are metal.

9. The accelerometer according to claim 1 wherein the body and the posts are formed as a monolithic, one-piece, metal structure.

10. The accelerometer according to claim 1 wherein the piezoplates are quartz.

11. The accelerometer according to claim 3 wherein a total of mass of the seismic masses and piezoplates of each linear accelerometer is substantially the same.

12. The accelerometer according to claim 1, further comprising a common housing enclosing the first and second linear accelerometers.

13. The rotational accelerometer of claim 1, including:

third and fourth spaced-apart linear accelerometers each having first and second piezoplates and corresponding first and second seismic mass clamped to a corresponding post;

the piezoplates of each of the third and fourth linear accelerometer having axis of sensitivity parallel to the first axes and being electrically connected to be sensitive to linear acceleration along the parallel first axes;

each of the post being connected to a body so that the first axes of both of the third and fourth linear accelerometers are parallel; and

the polarity of the third and fourth linear accelerometers being opposed and electrically connected to be sensitive in combination to rotational acceleration about a third axis orthogonal to the first and second axes.

14. The rotational accelerometer of claim 13, wherein the posts of the third and fourth linear accelerometers are substantially collinear and extend substantially orthogonally from the body and orthogonal to the post of the first and second linear accelerometers.

15. The rotational accelerometer of claim 13, wherein:

the post, the piezoplates, and the seismic masses of the first linear accelerometer each have a first bore therein;

the post, the piezoplates, and the seismic masses of the second linear accelerometer each have a second bore therein;

a first metal bolt extending through each of the first bores and clamping each of the piezoplates and seismic masses to the post, the first bolt contacting neither the piezoplates nor the post;

a second metal bolt passing through each of the second bores and clamping each of the piezoplates and seismic masses to the post, the second bolt contacting neither the piezoplates nor the post;

the post, the piezoplates, and the seismic masses of the third linear accelerometer each have a third bore therein;

the post, the piezoplates, and the seismic masses of a fourth linear accelerometer each have a fourth bore therein;

a third metal bolt extends through each of the third bores and clamps each of the piezoplates and seismic masses to the post, the third metal bolt contacting neither the piezoplates nor the post; and

a fourth metal bolt passing through each of the fourth bores and clamping each of the piezoplates and seismic masses to the post, the fourth bolt contacting neither the piezoplates nor the post.

16. The accelerometer of claim 15, further comprising:

an electrical connection between the first bolt and a first electric terminal;

an electrical connection between the second bolt and the first electric terminal;

an electrical connection between the body and a second electrical terminal, such that an electrical instrument can read a signal from between the first and second electrical terminals;

an electrical connection between the third metal bolt and a third electric terminal;

an electrical connection between either the fourth bolt or one of the masses of the fourth linear accelerometer and the third electric terminal; and

an electrical connection to a second electric terminal, the second electric terminal comprising a ground, enabling an electrical instrument to read a signal from between the second and third electric terminals.

17. The accelerometer as in claim 16, wherein the first, second, third and fourth linear accelerometer'"'"'s posts are metal and are electrically connected to one another.

18. The accelerometer of claim 17, wherein the body, as well as the posts are all formed as a monolithic, one-piece metal structure.

19. The rotational accelerometer of claim 1, including:

third, fourth, fifth and sixth spaced-apart linear accelerometers each having first and second piezoplates and corresponding first and second seismic mass clamped to a corresponding post;

the piezoplates of each of the third and fourth linear accelerometers having axis of sensitivity parallel to the second axis and being electrically connected to be sensitive to linear acceleration along the second parallel axes;

the piezoplates of each of the fifth and sixth linear accelerometers having axis of sensitivity parallel to the third axis and being electrically connected to be sensitive to linear acceleration along the parallel third axes;

each of the post of the third and fourth linear accelerometers being connected to a body so that the parallel second axes of both of the third and fourth linear accelerometers are parallel;

each of the post fifth and sixth linear accelerometers being connected to a body so that the parallel third axes of both of the fifth and sixth linear accelerometers are parallel;

the polarity of the third and fourth linear accelerometers being opposed and electrically connected to be sensitive in combination to rotational acceleration about the third axis; and

the polarity of the fifth and sixth linear accelerometers being opposed and electrically connected to be sensitive in combination to rotational acceleration about the first axis.

20. The rotational accelerometer of claim 19, wherein the posts of the third and fourth linear accelerometers are substantially collinear;

the posts of the fifth and sixth linear accelerometers are substantially collinear; and

the posts of the third and fourth linear accelerometers, the posts of the fifth and sixth linear accelerometers and the post of the first and second linear accelerometers are substantially mutually orthogonal.

21. The rotational accelerometer of claim 19, wherein:

the post, the piezoplates, and the seismic masses of the first linear accelerometer each have a first bore therein;

the post, the piezoplates, and the seismic masses of the second linear accelerometer each have a second bore therein;

a first metal bolt extending through each of the first bores and clamping each of the piezoplates and seismic masses to the post, the first bolt contacting neither the piezoplates nor the post;

a second metal bolt passing through each of the second bores and clamping each of the piezoplates and seismic masses to the post, the second bolt contacting neither the piezoplates nor the post;

the post, the piezoplates, and the seismic masses of the third linear accelerometer each have a third bore therein;

the post, the piezoplates, and the seismic masses of the fourth linear accelerometer each have a fourth bore therein;

a third metal bolt extends through each of the third bores and clamps the piezoplates and seismic masses to the post, the third metal bolt contacting neither the piezoplates nor the post;

a fourth metal bolt passing through each of the fourth bores and clamping the piezoplates and seismic masses to the post, the fourth bolt contacting neither the piezoplates nor the post;

the post, the piezoplates, and the seismic masses of the fifth linear accelerometer each have a fifth bore therein;

the post, the piezoplates, and the seismic masses of the sixth linear accelerometer each have a sixth bore therein; and

,

a fifth metal bolt extends through each of the fifth bores and clamps the piezoplates and seismic masses to the post, the fifth metal bolt contacting neither the piezoplates nor the post;

a sixth metal bolt passes through each of the fifth bores and clamps the piezoplates and seismic masses to the post, the sixth bolt contacting neither the piezoplates nor the post.

22. The accelerometer of claim 21, further comprising:

an electrical connection between the first bolt and a first electric terminal;

an electrical connection between the second bolt and the first electric terminal;

an electrical connection between the body and a second electrical terminal, enabling an electrical instrument to read the signal from between the first and second electrical terminals;

an electrical connection between the third metal bolt and a third electric terminal;

an electrical connection between either the fourth bolt or one of the masses of the fourth linear accelerometer and the third electric terminal, enabling an electrical instrument to read the signal from between the second and third electric terminals;

an electrical connection from the fifth bolt to a fourth electrical terminal;

an electrical connection from the sixth bolt to the fourth electrical terminal, enabling

an electrical instrument to read the signal from between the fourth and second electric terminals.

23. The accelerometer as in claim 21, wherein the posts are metal and electrically interconnected with one another.

24. The accelerometer as in claim 21, wherein the body and each of the posts are a monolithic, one-piece metal structure.

25. A method of calibrating a rotational accelerometer comprising the steps of:

selecting a pair of first piezoelectric plates, a pair of first seismic masses, and one first bolt;

selecting a pair of second piezoelectric plates, a pair of second seismic mass, and one second bolt;

ensuring that the total weight of the first plates, the first bolt, and the first seismic masses is equal to the total weight of the second piezoplates, the second bolt, arid the second seismic masses;

constructing a first shear-type linear accelerometer from the first piezoplates and the first seismic masses;

constructing a second shear-type linear accelerometer from the second piezoplates and the second seismic masses;

aligning the first and second linear accelerometers on a body to have opposed polarity and parallel axes of sensitivity; and

electrically connecting the linear accelerometers to a common port so as to measure in combination angular acceleration about an axis perpendicular to the axes of sensitivity.

26. The method of claim 25, wherein the piezoelectric plates are selected to be shear plates made of quartz.