Coplanar proofmasses employable to sense acceleration along three axes

• US 20050145029A1
• Filed: 12/13/2004
• Published: 07/07/2005
• Est. Priority Date: 01/07/2004
• Status: Active Grant

• Current Assignee: Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Original Assignee: Litton Systems Incorporated
• Inventors: Stewart, Robert E.
• Granted Patent: US 7,178,398 B2
• Time in Patent Office: Days
• US Class Current: 73/514.10
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 15/18 in two or more dimensions
• CPC Class Codes: G01P 2015/0828 the mass being of the paddle type being suspended at one of its longitudinal ends
• CPC Class Codes: G01P 2015/0831 the mass being of the paddle type having the pivot axis between the longitudinal ends of the mass, e.g. see-saw configuration

Abstract

An apparatus in one example comprises a first proofmass employable to sense a first acceleration along a first input axis; a second proofmass employable to sense a second acceleration along a second input axis; and a third proofmass employable to sense a third acceleration along a third input axis. The first input axis, the second input axis, and the third input axis are substantially orthogonal. The first proofmass, the second proofmass, and the third proofmass are substantially coplanar.

Claims

1. An apparatus, comprising:

a first proofmass employable to sense a first acceleration along a first input axis;

a second proofmass employable to sense a second acceleration along a second input axis; and

a third proofmass employable to sense a third acceleration along a third input axis;

wherein the first input axis, the second input axis, and the third input axis are substantially orthogonal;

wherein the first proofmass, the second proofmass, and the third proofmass are substantially coplanar.

2. The apparatus of claim 1, wherein each of the first proofmass, the second proofmass, and the third proofmass comprise one or more voids, a center of geometry, and a center of mass;

wherein the one or more voids serve to position the center of mass below the center of geometry.

3. The apparatus of claim 2, wherein the one or more voids are positioned in the first proofmass, the second proofmass, and the third proofmass to orient the first input axis, the second input axis, and the third input axis into three substantially orthogonal directions.

4. The apparatus of claim 3, wherein the first proofmass, the second proofmass, and the third proofmass lie substantially in a plane;

wherein the one or more voids in the first and second proofmasses orient the first and second input axes in an in-plane direction;

wherein the first proofmass is positioned relative to the second proofmass in the plane to orient the first input axis to be orthogonal to the second input axis;

wherein the one or more voids in the third proofmass serve to position the center of mass of the third proofmass below the center of geometry and to a side of an axis of rotation of the third proofmass to orient the third input axis into an out-of-plane direction orthogonal to the first and second input axes.

5. The apparatus of claim 1, wherein the first proofmass comprises a cross-leaf flexure that couples the first proofmass with a frame;

wherein the cross-leaf flexure comprises a first flexure beam and a second flexure beam;

wherein the first, second, and third proofmasses lie substantially in a plane, wherein the first flexure beam is substantially parallel with the plane, wherein the second flexure beam is substantially orthogonal to the plane.

6. The apparatus of claim 5, wherein the second flexure beam serves to promote a reduction in compliancy of the cross-leaf flexure in a direction out of the plane.

7. The apparatus of claim 1, wherein the third proofmass is positioned relative to the first and second proofmasses so the first input axis, the second input axis, and the third input axis intersect at a common point to simplify compensation algorithms during calculation of one or more of the first acceleration, the second acceleration, and the third acceleration.

8. The apparatus of claim 1, wherein one or more of the first proofmass, the second proofmass, and/or the third proofmass comprise one or more holes that serve to reduce squeeze film gas damping and associated noise in a measurement of one or more of the first acceleration, the second acceleration, and/or the third acceleration.

9. The apparatus of claim 1, further comprising a top cover and a bottom cover;

wherein the first proofmass, the second proofmass, and the third proofmass are formed in a substrate layer;

wherein the substrate layer is encapsulated between the top and bottom covers, wherein the top and bottom covers comprise one or more electrodes aligned to sense displacement of the first, second, and third proofmasses, and return the displacement to null.

10. The apparatus of claim 9, further comprising one or more dielectric layers between the substrate layer and one or more of the top and bottom covers, wherein the one or more dielectric layers comprise openings that provide space for displacement of the first, second, and third proofmasses.

11. The apparatus of claim 9, further comprising one or more electrical paths;

wherein one or more of the top and bottom covers comprises an outer surface with one or more electrical contacts;

wherein the electrical paths route signals between the one or more electrical contacts and one or more of the first proofmass, the second proofmass, the third proofmass, and the one or more electrodes;

wherein the one or more electrical contacts serve to electrically and mechanically connect with a separate layer.

12. A process, comprising the steps of:

etching three coplanar proofmasses into a substrate, wherein the three coplanar proofmasses are employable to sense acceleration along three respective input axes; and

etching one or more voids into the three coplanar proofmasses to orient the three respective input axes into three orthogonal acceleration sensing directions.

13. The process of claim 12, further comprising the step of:

forming one or more flexure components to support the three coplanar proofmasses, wherein the one or more flexure components comprise a first beam substantially parallel with a plane of the three proofmasses and a second beam substantially orthogonal to the plane to promote a reduction in compliancy of the one or more flexure components in a direction out of the plane.

14. The process of claim 12, wherein the step of etching the three coplanar proofmasses into the substrate comprises the steps of:

positioning the three proofmasses in the substrate so the three input axes are aligned in three orthogonal directions; and

positioning the third proofmass relative to the first and second proofmasses so the three input axes intersect at a common point.

15. The process of claim 12, further comprising the step of:

etching one or more holes into one or more of the three coplanar proofmasses that serve to reduce squeeze film gas damping and associated noise in a measurement of the acceleration along the three respective input axes.

16. An apparatus, comprising:

a first proofmass employable to sense a first acceleration along a first input axis;

a second proofmass employable to sense a second acceleration along a second input axis; and

a third proofmass employable to sense a third acceleration along a third input axis;

wherein the first proofmass, the second proofmass, and the third proofmass are substantially coplanar;

wherein the first input axis, the second input axis, and the third input axis intersect at a common point and are substantially orthogonal.

17. The apparatus of claim 16, wherein the first proofmass comprises a cross-leaf flexure that couples the first proofmass with a frame;

wherein the cross-leaf flexure comprises a first flexure component and a second flexure component;

wherein the first flexure component comprises a first flexure portion that is substantially parallel with the first input axis, wherein the second flexure component comprises a second flexure portion that is substantially orthogonal to the first flexure portion.

18. The apparatus of claim 17, wherein the first proofmass lays substantially in a plane;

wherein the second flexure portion of the second flexure component serves to promote a reduction in compliancy of the first proofmass in a direction out of the plane.

19. The apparatus of claim 16, wherein each of the first proofmass, the second proofmass, and the third proofmass comprise one or more voids, a center of geometry, and a center of mass;

wherein the one or more voids position the center of mass below the center of geometry;

wherein the first input axis, the second input axis, and the third input axis are oriented into orthogonal directions based on a placement of the one or more voids in the first proofmass, the second proofmass, and the third proofmass.

20. The apparatus of claim 16, wherein the third proofmass is positioned relative to the first proofmass and the second proofmass so the first input axis, the second input axis, and the third input axis intersect at a common point to simplify compensation algorithms during calculation of one or more of the first acceleration, the second acceleration, and the third acceleration.

21. An apparatus, comprising:

a first proofmass employable to sense a first acceleration along a first input axis;

a second proofmass employable to sense a second acceleration along a second input axis;

a third proofmass employable to sense a third acceleration along a third input axis; and

a plurality of cross-leaf flexures that couple the first proofmass, the second proofmass, and the third proofmass with a frame;

wherein the first proofmass, the second proofmass, and the third proofmass are substantially coplanar.