Micromachined rate and acceleration sensor

• US 5,557,046 A
• Filed: 03/07/1994
• Issued: 09/17/1996
• Est. Priority Date: 02/08/1991
• Status: Expired due to Fees

• Current Assignee: L-3 Communications Corporation (L3Harris Technologies, Inc.)
• Original Assignee: Alliedsignal Inc. (Honeywell International Inc.)
• Inventors: Hulsing, Rand H. II
• Primary Examiner(s): CHAPMAN JR, JOHN E
• Application Number:
  US08/207,328
• Time in Patent Office: 925 Days
• Field of Search: 73/505, 73/510, 73/511, 73/517 R, 73/517 AV
• US Class Current: 73/504.04
• CPC Class Codes: F02G 1/044 having at least two working members, e.g. pistons, delivering power output
• CPC Class Codes: F02G 1/0445 Engine plants with combined cycles, e.g. Vuilleumier
• CPC Class Codes: F02G 2250/18 Vuilleumier cycles
• CPC Class Codes: F02G 2253/03 Stem seals
• CPC Class Codes: F16F 2230/0052 Physically guiding or influencing
• CPC Class Codes: F16F 2230/34 Flexural hinges
• CPC Class Codes: F16L 37/24 in which the connection is made by inserting one member axially into the other and rotating it to a limited extent, e.g. with bayonet action
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis
• CPC Class Codes: G01C 19/5747 each sensing mass being connected to a driving mass, e.g. driving frames
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/097 by vibratory elements
• 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: Y10S 73/01 Vibration

Abstract

A sensor (10) is disclosed for measuring the specific force and angular rotation rate of a moving body and is micromachined from a silicon substrate (16). First and second accelerometers (32a and b) are micromachined from the silicon substrate (16), each having a force sensing axis (38) and producing an output signal of the acceleration of the moving body along its force sensing axis (38). The first and second accelerometers (32a and b) are mounted within the substrate (16) to be moved along a vibration axis (41). The first and second accelerometers (32a and b) are vibrated or dithered to increase the Coriolis component of the output signals from the first and second accelerometers (32a and b). A sinusoidal drive signal of a predetermined frequency is applied to a conductive path (92) disposed on each of the accelerometers. Further, magnetic flux is directed to cross each of the conductive paths (92), whereby the interaction of the magnetic flux and of the drive signal passing therethrough causes the desired dithering motion. A link (72) is formed within the silicon substrate (16) and connected to each of the accelerometers (32a and b), whereby motion imparted to one results in a like, but opposite motion applied to the other accelerometer (32). Further, a unitary magnet (20) and its associated flux path assembly direct and focus the magnetic flux through the first and second accelerometers (32a and b) formed within the silicon substrate (16).

Claims

1. A sensing device for measuring the linear acceleration and rate of rotation of a moving body, comprising:

a monolithic substrate having first and second substantially planar surfaces disposed substantially parallel to each other;

first and second accelerometers formed of said substrate, each of said accelerometers having a force sensing axis for producing an output signal indicative of the acceleration of the moving body along said force sensing axis, each of said accelerometers further having

an accelerometer frame,

a proof mass,

hinge means interconnected between said frame and said proof mass for allowing said proof mass to rotate about a hinge axis when the moving body is subjected to a force along said force sensing axis, said proof mass having a first end interconnected by said hinge means to said frame and a free end permitted to rotate freely about said hinge axis with respect to said frame, said proof mass further having a center of gravity and a pendulous axis aligned to intersect said center of gravity and said hinge axis;

flexible means interconnected between said frame and said free end of said proof mass for flexibly restraining the pivoting of said proof mass about said pendulous axis;

a dither frame;

flexure means for connecting the accelerometer frame of each of said first and second accelerometers to said dither frame, said flexure means being generally compliant to allow dithering of said first and second accelerometers along a dither axis, said dither axis being generally perpendicular to said force sensing axes of said first and second accelerometers;

a conductive dither path disposed along at least said flexure means;

means for directing a magnetic flux to cross the conductive dither path;

signal generator means for producing and applying to said conductive dither path a periodic dither drive signal to dither said first and second accelerometers along said dither axis;

a unitary magnet for emanating flux from first and second surfaces thereof, and magnetic circuit means for establishing a flux path between said second surface of said monolithic substrate and said second surface of said unitary magnet, said magnetic circuit means including a portion disposed adjacent said second planar surface of said monolithic substrate, said magnetic circuit portion concentrating said magnetic flux through said conductive dither path.

2. A sensing device for measuring the linear acceleration and rate of rotation of a moving body, comprising:

a monolithic substrate having first and second substantially planar surfaces disposed substantially parallel to each other;

first and second accelerometers formed of said substrate, each of said accelerometers having a force sensing axis for producing an output signal indicative of the acceleration of the moving body along said force sensing axis, each of said accelerometers further having

an accelerometer frame,

a proof mass,

hinge means interconnected between said frame and said proof mass for allowing said proof mass to rotate about a hinge axis when the moving body is subjected to a force along said force sensing axis, said proof mass having a first end interconnected by said hinge means to said frame and a free end permitted to rotate freely about said hinge axis with respect to said frame, said proof mass further having a center of gravity and a pendulous axis aligned to intersect said center of gravity and said hinge axis;

flexible means interconnected between said frame and said free end of said proof mass for flexibly restraining the pivoting of said proof mass about said pendulous axis;

a dither frame;

flexure means for connecting the accelerometer frame of each of said first and second accelerometers to said dither frame, said flexure means being generally compliant to allow dithering of said first and second accelerometers along a dither axis, said dither axis being generally perpendicular to said force sensing axes of said first and second accelerometers;

a conductive dither path disposed along at least said flexure means;

means for directing a magnetic flux to cross the conductive dither path, said conductive dither path having an effective length disposed within said magnetic flux, and a reference conductive path having a length corresponding to said effective length of said conductive dither path, so that the impedances of said dither and reference conductive paths are substantially equal, said reference conductive path being disposed on at least one of said first and second planar surfaces; and

signal generator means for producing and applying to said conductive dither path a periodic dither drive signal to dither said first and second accelerometers along said dither axis.

3. The sensing device as claimed in claim 2, wherein said signal generator means comprises a bridge circuit including third and fourth impedance elements, said conductive dither path and said reference conductive path.

4. The sensing device as claimed in claim 3, wherein said bridge circuit comprises a first node interconnecting said first and second impedance elements, a second node interconnecting said first impedance element and said conductive dither path, a third node interconnecting said conductive dither path and said reference conductive path, and a fourth node interconnecting said reference conductive path and said second impedance element.

5. The sensing device as claimed in claim 4, wherein said signal generator means further comprises a first circuit means having first and second inputs connected respectively to said second and fourth nodes for providing an output signal indicative of the difference of the voltage induced by said magnetic flux across said dither and reference conductive paths, and a second circuit means for amplifying and applying said output signal as a feedback signal between said first and third nodes, whereby said periodic dither drive signal is developed across said conductive dither path.