Vibrating accelerometer-multisensor

• US 4,744,249 A
• Filed: 07/10/1986
• Issued: 05/17/1988
• Est. Priority Date: 07/25/1985
• Status: Expired due to Fees

• Current Assignee: Litton Systems Incorporated
• Original Assignee: Litton Systems Incorporated
• Inventors: Stewart, Robert E.
• Primary Examiner(s): Chapman, John
• Application Number:
  US06/884,115
• Time in Patent Office: 677 Days
• Field of Search: 73/505, 73/510, 73/516 R, 73/517 R, 73/517 B, 73/514
• US Class Current: 73/504.04
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 15/131 with electrostatic counterbalancing means
• 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

Abstract

A vibrating multisensor, each using two accelerometers which are vibrated along straight lines perpendicular to their sensing axes. In one embodiment, the sensing axes are co-linear, and in another embodiment the sensing axes are perpendicular. The accelerometers preferably use a proof mass and flexure suspension made on a silicon wafer sandwiched between two other wafers that carry electrodes both for sensing displacement and forcing of the central accelerometer wafer.

Claims

1. A multisensor, responsive to the linear acceleration and rate of rotation of a body comprising, in combination:

(a) a first accelerometer responsive to linear acceleration along a first preselected sensing axis;

(b) a second accelerometer responsive to linear acceleration along a second preselected sensing axis;

(c) a pair of double diaphragm suspensions, including an electromagnet mounted between said double diaphragm suspensions, arranged and positioned to constrain said accelerometers so that said first preselected sensing axis is orthogonal to said second preselected sensing axis;

(d) means for vibrating said accelerometers out of phase; and

(e) means connected to receive the output signals of said accelerometers and to separate signals which are measures of the Coriolis accelerations exerted upon said accelerometers from signals caused by acceleration along the respective sensing axes of said accelerometers.

2. Apparatus as defined in claim 1, wherein the vibration frequency of said double diaphragm suspensions is high relative to system bandwidth.

3. Apparatus as defined in claim 2 wherein said first and second accelerometers are A4 MOD IVs.

4. A multisensor, responsive to the linear acceleration and rate of rotation of a body comprising, in combination:

(a) a first accelerometer responsive to linear acceleration along a first preselected sensing axis;

(b) a second accelerometer responsive to linear acceleration along a second preselected sensing axis;

(c) each of said first and second accelerometers comprising a first planar substrate of semiconductor material having an opening therein that defines the periphery of an acceleration sensitive mass;

said acceleration sensitive mass being connected to said semiconductor substrate by a plurality of crossed beam flexure blades formed by anisotropic etching of a single crystal of silicon;

second and third planar substrates mounted on opposite sides of said first planar substrate, each having a conductive surface adjacent said acceleration sensitive mass;

means for applying an electrical potential between said acceleration sensitive mass and said conductive surfaces on said second and third substrates; and

electrical integrated circuit means formed within said semiconductor material of said first planar substrate to connect said electrical potential to said acceleration sensitive mass;

(d) a pair of double-diaphragm suspensions, arranged and positioned to constrain said accelerometers so that said first preselected sensing axis is orthogonal to said second preselected sensing axis;

(e) means for vibrating said accelerometers in phase opposition; and

(f) means connected to receive the output signals of said accelerometers and to separate signals which are measures of the Coriolis accelerations exerted upon said accelerometers from signals caused by acceleration along the respective sensing axes of said accelerometers.

5. Apparatus as claimed in claim 4, wherein:

said means formed within said semiconductor material of each said accelerometer further include electronic means responsive to the output signal of that said accelerometer.

6. Apparatus as claimed in claim 4, wherein:

in each of said accelerometers, said crossed beam flexure blades provide for a cantilevered flexure in one direction and rigidity in all other directions.

7. Apparatus as claimed in claim 4, wherein:

in each of said accelerometers, said crossed beam flexures blades are formed in pairs, each blade formed by two V-shaped grooves in opposite surfaces of said semiconductor substrate which form a blade at an angle to the plane of said substrate, each blade of said pair being at an opposite angle to the other.

8. Apparatus as claimed in claim 4, wherein:

in each of said accelerometers, said acceleration sensitive mass has a waffle-like pattern to create a large surface area-to-mass ratio.

9. Apparatus as recited in claim 4, wherein:

in each of said accelerometers, said second and third substrates are formed of nonconductive material.

10. Apparatus as recited in claim 4, wherein:

in each of said accelerometer, said acceleration sensitive mass is formed within said substrate of semiconductor material by doping said material to become conductive; and

said second and third planar substrates are formed by a pair of insulated plates mounted on opposite sides of said semiconductor material and have electrically conductive pads disposed thereon adjacent said acceleration sensitive mass.