Micromachined rate and acceleration sensor

• US 5,341,682 A
• Filed: 06/08/1993
• Issued: 08/30/1994
• Est. Priority Date: 02/08/1991
• Status: Expired due to Fees

• Current Assignee: L-3 Communications Corporation (L3Harris Technologies, Inc.)
• Original Assignee: Alliedsignal Inc.
• Inventors: Hulsing, Rand H. II
• Primary Examiner(s): CHAPMAN JR, JOHN E
• Application Number:
  US08/073,814
• Time in Patent Office: 448 Days
• Field of Search: 73/505, 73/510, 73/511, 73/517 AU, 73/517 R
• 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. Apparatus for measuring the specific force and angular rotation rate of a moving body, comprising:

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

b) a first accelerometer formed of said substrate and having a first force sensing axis for producing a first output signal indicative of the acceleration of the moving body along said first force sensing axis, said first accelerometer having a proof mass, a support frame, and at least one flexure connecting said proof mass to said support frame;

c) a second accelerometer formed of said substrate and having a second force sensing axis for producing a second output signal indicative of the acceleration of the moving body along said second force sensing axis, said second accelerometer having a proof mass, a support frame, and at least one flexure connecting said proof mass to said support frame;

d) a dither frame formed of said substrate, said dither frame being of a rectangular configuration having first and third opposing members and second and fourth opposing members;

e) a first pair of S-bend flexures connected between said support frame of said first accelerometer and said dither frame, and a second pair of S-bend flexures connected between said support frame of said second accelerometer and said dither frame, said S-bend flexures being formed of said substrate for mounting said first and second accelerometers such that said first and second force sensing axes are both oriented at the same angle with respect to said first and second surfaces and such that said first and second accelerometers can be moved along a vibration axis perpendicular to each of said first and second sensing axes;

f) link means having first and second points connected respectively to said first and second accelerometers, a pivoting point disposed intermediate between said first and second connected points, and support means for affixedly disposing said pivot point with respect to said frame to permit said link means to pivot there about and, when one of said first and second accelerometers is moved, to impart an equal and opposite motion to said other of said first and second accelerometers;

g) drive means coupled to each of said first and second accelerometers for imparting a dithering motion thereto of a predetermined frequency along said vibration axis; and

h) said substrate having a rate axis perpendicular to each of said first and second force sensing axes and said vibration axis, whereby said first and second output signals have a Coriolis component indicative of the angular rotation of he moving body about said axis.

2. The measuring apparatus as claimed in claim 1, wherein said support means comprises a pivot flexure comprising said pivot point.

3. The measuring apparatus as claimed in claim 2, wherein said pivot flexure has a length and cross-sectional dimensions such that said flexure flexes with a simple bend.

4. The measuring apparatus as claimed in claim 3, wherein said link means comprises first and second arms and a U-shaped member disposed there between and interconnecting said first and second arms, said pivot flexure having a distal end connected to said U-shaped member, whereby said pivot point is aligned with said first and second arms extending therefrom in radial fashion.

5. The measuring apparatus as claimed in claim 1, wherein there is included first and second connecting flexures for respectively connecting said first and second points of said link means to said first and second accelerometers.

6. The measuring apparatus as claimed in claim 5, wherein each of said first and second connecting flexures have a length and cross-sectional dimensions selected such that each of said first and second connecting flexures flex with approximately 50% simple and 50% "S-bend" movements.

7. The measuring apparatus as claimed in claim 5, wherein said first and second connecting flexures are connected respectively to that end of each of said first and second accelerometer opposite from said first and second flexure means.

8. The measuring apparatus as claimed in claim 1, wherein a conductive path is disposed on one of said first and second surfaces to traverse said first and second accelerometers.

9. The measuring apparatus as claimed in claim 8, wherein said conductive path extends across one flexure of each of said first and second pairs and across said link means.

10. The measuring apparatus as claimed in claim 9, wherein there is included signal generator means for producing and applying a periodic drive signal having a predetermined frequency to said conductive path, and magnetic flux producing means for producing and directing a magnetic flux to cross said conductive path, whereby the interaction of said magnetic flux and said drive signal passing through said conductive path cause said first and second accelerometers to vibrate along said vibration axis at said pre-determined frequency.

11. The measuring apparatus as claimed in claim 10, wherein said conductive path traverses that one flexure of each of said first and second pairs disposed closest to said link means.

12. The measuring apparatus as claimed in claim 11, wherein said conductive path has a centerpoint and there is further included means for connecting said centerpoint to ground.

13. The measuring apparatus as claimed in claim 12, wherein said connecting means comprises a second conductive path extending along said support means and said pivot flexure to said frame.

14. The measuring apparatus as claimed in claim 10, wherein there is included a second, reference conductive path having a length equal to that of said first mentioned conductive path.

15. Apparatus for measuring the specific force and angular rotation rate of a moving body, comprising:

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

b) a first accelerometer formed of said substrate and having a first force sensing axis for producing a first output signal indicative of the acceleration of the moving body along said first force sensing axis, said first accelerometer having a proof mass, a support frame, and at least one flexure connecting said proof mass to said support frame;

c) a second accelerometer formed of said substrate and having a second force sensing axis for producing a second output signal indicative of the acceleration of the moving body along said second force sensing axis, said second accelerometer having a proof mass, a support frame, and at least one flexure connecting said proof mass to said support frame;

d) a dither frame formed of said substrate, said dither frame being of a rectangular configuration having first and third opposing members and second and fourth opposing members;

e) a first pair of S-bend flexures connected between said support frame of said first accelerometer and said dither frame, and a second pair of S-bend flexures connected between said support frame of said second accelerometer and said dither frame, said S-bend flexures being formed of said substrate for mounting said first and second accelerometers such that said first and second force sensing axes are both oriented at the same angle with respect to said first and second surfaces and such that said first and second accelerometers can be moved along a vibration axis perpendicular to each of said first and second sensing axes;

f) link means having first and second points connected respectively to said first and second accelerometers and a pivoting point disposed a radial length from each of said first and second connected points, support means for mounting said pivoting point on one of said first and third members of said frame to permit said link means to pivot about said pivoting point and when one of said first accelerometers if moved, to impart an equal and opposite motion to said other of said first and second accelerometers, each flexure of said first and second pairs for providing an effective radius of a length equal to that of said radial length of said link means;

g) drive means coupled to each of said first and second accelerometers for imparting a dithering motion thereto of a predetermined frequency along said vibration axis; and

h) said substrate having a rate axis perpendicular to each of said first and second force sensing axes and said vibration axis, whereby said first and second output signals have a Coriolis component indicative of the angular rotation of the moving body about said rate axis.

16. The measuring apparatus as claimed in claim 15, wherein each of said first and second accelerometers has a rectangular configuration including first and third opposing peripheral edges, and second and fourth opposing peripheral edges, said first and second pairs of flexures being connected respectively to said third and first peripheral edges of said first and second accelerometers such that each of their first and third opposing peripheral edges move substantially parallel with respect to said first and third opposing members of said dither frame.

17. Apparatus for measuring the specific force and angular rotation rate of a moving body, comprising:

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

b) a first accelerometer formed of said substrate and having a first force sensing axis for producing a first output signal indicative of the acceleration of the moving body along said first force sensing axis, said first accelerometer having a proof mass, a support frame, and at least one flexure connecting said proof mass to said support frame;

c) a second accelerometer formed of said substrate and having a second force sensing axis for producing a second output signal indicative of the acceleration of the moving body along said second force sensing axis, said second accelerometer having a proof mass, a support frame, and at least one flexure connecting said proof mass to said support frame;

d) a dither frame formed of said substrate;

e) a first pair of flexures connected between said support frame of S-bend said first accelerometer and said dither frame, and a second pair of S-bend flexures connected between said support frame of said second accelerometer and said dither frame, said flexures being formed of said substrate for mounting said first and second accelerometers such that said first and second force sensing axes are both oriented at the same angle with respect to said first and second surfaces and such that said first and second accelerometers can be moved along a vibration axis perpendicular to each of said first and second sensing axes;

f) link means having first and second points connected respectively to said first and second accelerometers, a pivoting point disposed intermediate between said first and second connected points, and support means for affixedly disposing said pivot point with respect to said frame to permit said link means to pivot thereabout and, when one of said first and second accelerometers is moved, to impart an equal and opposite motion to said other of said first and second accelerometers.

h) said substrate having a rate axis perpendicular to each of said first and second force sensing axes and said vibration axis.

18. The measuring apparatus as claimed in claim 17, wherein said support means comprises a pivot flexure comprising said pivot point.

19. The measuring apparatus as claimed in claim 18, wherein said pivot flexure has a length and cross-sectional dimensions such that said flexure flexes with a simple bend.

20. The measuring apparatus as claimed in claim 19, wherein said link means comprises first and second arms and a U-shaped member disposed there between and interconnecting said first and second arms, said pivot flexure having a distal end connected to said U-shaped member, whereby said pivot point is aligned with said first and second arms extending therefrom in radial fashion.

21. The measuring apparatus as claimed in claim 17, wherein there is included first and second connecting flexures for respectively connecting said first and second points of said link means to said first and second accelerometers.

22. The measuring apparatus as claimed in claim 21, wherein each of said first and second connecting flexures have a length and cross-sectional dimensions selected such that each of said first and second connecting flexures flex with approximately 50% simple and 50% "S-bend" movements.

23. The measuring apparatus as claimed in claim 17, wherein a conductive path is disposed on one of said first and second surfaces to traverse said first and second accelerometers.

24. The measuring apparatus as claimed in claim 23, wherein said conductive path extends across one flexure of each of said first and second pairs and across said link means.

25. The measuring apparatus as claimed in claim 24, wherein there is included signal generator means for producing and applying a periodic drive signal having a predetermined frequency to said conductive path, and magnetic flux producing means for producing and directing a magnetic flux to cross said conductive path, whereby the interaction of said magnetic flux and said drive signal passing through said conductive path cause said first and second accelerometers to vibrate along said vibration axis at said pre-determined frequency.

26. The measuring apparatus as claimed in claim 25, wherein said conductive path traverses that one flexure of each of said first and second pairs disposed closest to said link means.

27. The measuring apparatus as claimed in claim 17, wherein each of said first and second accelerometers has a rectangular configuration including first and third opposing peripheral edges, and second and fourth opposing peripheral edges, said first and second pairs of flexures being connected respectively to said third and first peripheral edges of said first and second accelerometers such that each of their first and third opposing peripheral edges move substantially parallel with respect to first and second opposing members of said dither frame.