Monolithic vibrating beam angular velocity sensor

• US 6,250,158 B1
• Filed: 05/09/1997
• Issued: 06/26/2001
• Est. Priority Date: 05/09/1997
• Status: Expired due to Fees

• Current Assignee: Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Original Assignee: Litton Systems Incorporated
• Inventors: Stewart, Robert E.
• Primary Examiner(s): CHAPMAN JR, JOHN E
• Application Number:
  US08/854,240
• Time in Patent Office: 1,509 Days
• Field of Search: 735/041.4, 735/041.2, 735/041.5, 735/041.6, 310/329
• US Class Current: 73/504.14
• CPC Class Codes: G01C 19/5656 the devices involving a micromechanical structure

Abstract

A monolithic angular velocity sensor is formed from a common planar silicon substrate. Sensor element(s) comprising elongated beams is/are suspended within framed apertures formed within the common substrate. Transverse members, or ears, secure the elongated beam(s) to the frame and to the nodal points of the beam(s). Both single beam and multiple beam array sensors may be formed within a common silicon substrate. Orthogonally-directed beams, or arrays of beams, formed with a common substrate, permit angular velocity measurements about two orthogonal axes.

Claims

1. An angular velocity sensor comprising, in combination:

a) an elongated beam;

b) a frame having an internal aperture for accommodating said beam, the top and bottom surfaces of said frame and said beam being substantially parallel;

c) means for suspending said beam within said aperture, said means including (i) two pairs of aligned transverse members, (ii) each of said members being fixed at its opposed ends to an inner edge of said frame and to a major edge of said beam and (iii) each of said transverse members being fixed to a nodal point of said beam;

d) a first layer of electroceramic material fixed to said beam for flexibly driving said beam;

e) a second layer of electroceramic material fixed to said beam for detecting the presence and magnitude of Coriolis force exerted upon said beam;

f) said layers of electroceramic material being fixed to the top and bottom surfaces of said beam;

g) said beam, said means for suspending and said frame being an integral structure comprising silicon;

h) a drive electrode and a pair of pickoff electrodes located at the top and bottom surface of said beam;

i) each of said electrodes being separated from the surface of said beam by said layer of electroceramic material;

j) each of said electrode and underlying layers of electroceramic material being substantially identically patterned;

k) each of said drive electrodes is aligned along the major axis of said beam; and

l) a pair of said pickoff electrodes is aligned and symmetrically located with respect to each of said drive electrodes.

2. A monolithic angular velocity sensor comprising, in combination:

a) a plurality of mutually coupled sensor elements formed within a substantially-planar silicon substrate;

b) each of said sensor elements including an elongated beam;

c) the major axes of said sensor elements being aligned parallel to one another;

d) a frame having an internal aperture for accommodating said sensor elements;

e) means fixed to each of said beams for suspending said beams within said aperture whereby some of said beams are adjacent an inner edge of said aperture and others are solely adjacent other beams;

f) means fixed to each of said beams for flexibly driving said beams;

g) means fixed to each of said beams for detecting Coriolis force; and

h) said beams, said frame and said means for suspending comprising an integral structure.

3. A monolithic angular velocity sensor as defined in claim 2 wherein said means for suspending comprises:

a) two pairs of aligned transverse members;

b) one end of each of said aligned transverse members being fixed to a major side of a beam at a nodal point;

c) the opposed ends of transverse members of beams located adjacent an inner edge of said aperture being fixed thereto.

4. A monolithic angular velocity sensor as defined in claim 2 further characterized in that:

a) said means for flexibly driving comprises a layer of electroceramic material;

b) said means for detecting comprises a layer of electroceramic material;

c) the top and bottom surfaces of said frame and said beam being substantially parallel; and

d) said layers of electroceramic material being fixed to the top and bottom surface of said beam.

5. A monolithic angular velocity sensor as defined in claim 4 further including:

a) said means for driving additionally comprises a drive electrode and said means for detecting additionally comprises a pair of pickoff electrodes located at the top and bottom surfaces of said beam;

b) said electrodes being separated from the surface of said beam by said layers of electroceramic material; and

c) each of said electrodes and underlying layers of electroceramic material being of substantially identical dimensions.

6. A monolithic angular velocity sensor as defined in claim 5 further characterized in that:

a) each of said drive electrodes is aligned along the major axis of said beam; and

b) a pair of said pickoff electrodes is aligned and symmetrically located with respect to each of said drive electrodes.

7. A monolithic angular velocity sensor for sensing rotation rates about two orthogonal axes comprising, in combination:

a) a first sensor element;

b) a second sensor element;

c) said first and second sensor elements being formed within a silicon substrate;

d) each of said sensor elements including an elongated beam;

e) the major axes of said sensor elements being aligned orthogonal to one another;

f) a frame formed within said silicon substrate;

g) said frame having internal apertures for independently accommodating each of said elongated beams;

h) means for suspending each of said beams within an associated aperture, said means including (i) two pairs of aligned transverse members, (ii) each of said aligned transverse members being fixed at its opposed ends to an inner edge of said frame and to a major side of said beam and (iii) each of said transverse members being fixed to a nodal point of said beam;

i) a first layer of electroceramic material fixed to each of said beams for flexibly driving said beams;

j) a second layer of electroceramic material fixed to each of said beams for detecting the presence and magnitude of Coriolis force;

k) the top and bottom surfaces of said frame and said beams being substantially parallel to one another; and

l) said layers of electroceramic material being fixed to the top and bottom surfaces of said beams;

m) a drive electrode and a pair of pickoff electrodes located at the top and bottom surfaces of said beam;

n) each of said electrodes being separated from the surface of said beam by a layer of electroceramic material; and

o) each of said electrodes and underlying layers of electroceramic material being of substantially identical dimensions;

p) each of said drive electrodes being aligned along the major axis of said beam; and

q) a pair of said pickoff electrodes being aligned and symmetrically located with respect to each of said drive electrodes.

8. A monolithic angular velocity sensor for sensing rotation about two orthogonal axes comprising, in combination:

a) a first array of mutually-coupled sensor elements;

b) said first array including a first plurality of elongated beams aligned parallel to one another;

c) a second array of mutually-coupled sensor elements including a second plurality of elongated beams aligned parallel to one another;

d) the axes of the beams of the first array being aligned orthogonal to those of said second array;

e) each of said arrays being integral with a silicon substrate;

f) a frame having two internal apertures for accommodating said sensor elements;

g) means fixed to each of said beams for suspending said beams of said first array within one of said apertures and said beams of said second array within the other of said apertures whereby some of said beams are adjacent an inner edge of an aperture and others are solely adjacent other beams;

h) means fixed to each of said beams for flexibly driving said beams;

i) means fixed to each of said beams for detecting Coriolis force; and

j) said beams, said frame and said means for suspending comprising an integral structure.

9. A monolithic angular velocity sensor as defined in claim 8 wherein said means for suspending comprises:

a) two pairs of aligned transverse members;

b) one end of each of said aligned transverse members being fixed to a major side of a beam at a nodal point; and

c) the opposed ends of transverse members of beams located adjacent an inner edge of an aperture being fixed thereto.

10. A monolithic angular velocity sensor as defined in claim 8 further characterized in that:

a) said means for flexibly driving comprises a layer of electroceramic material;

b) said means for detecting comprises a layer of electroceramic material;

c) the top and bottom surfaces of said frame and said beam being substantially parallel; and

d) said layers of electroceramic material being fixed to the top and bottom surfaces of said beams.

11. A monolithic angular velocity sensor as defined in claim 10 further including:

a) said means for driving additionally comprises a drive electrode and said means for detecting additionally comprises a pair of pickoff electrodes located at the top and bottom surfaces of said beams;

b) said electrodes being separated from the surfaces of said beams by said layers of electroceramic material; and

c) each of said electrodes and underlying layers of electroceramic material being of substantially identical dimensions.

12. A monolithic angular velocity sensor as defined in claim 11 further characterized in that:

a) each of said drive electrodes is aligned along the major axis of said beam; and

b) a pair of said pickoff electrodes is aligned and symmetrically located with respect to each of said drive electrodes.