SOI-MEMS gyroscope having three-fold symmetry

• US 7,267,005 B1
• Filed: 03/02/2005
• Issued: 09/11/2007
• Est. Priority Date: 03/02/2005
• Status: Expired due to Fees

• Current Assignee: United States Secretary of the Army
• Original Assignee: United States Of America As Represented By The Secretary Of The Army (Government of the United States of America)
• Inventors: Kranz, Michael S., Holt, Sherrie Burgett
• Primary Examiner(s): CHAPMAN JR, JOHN E
• Application Number:
  US11/070,510
• Time in Patent Office: 923 Days
• Field of Search: 735/041.2, 735/041.4
• US Class Current: 73/504.14
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis

Abstract

A SOI-MEMS gyroscope has a three fold symmetrical construction such that is symmetrical in the x direction, the y direction and diagonally. The gyroscope is suspended above a silicon substrate by lateral flexures that are located at the corners of the proof mass and by central flexures that are positioned at the center regions of the proof mass. The proof mass, lateral flexures, and central flexures are formed of a silicon composition with the flexures supporting the proof mass such that the proof mass will not touch the underlying base silicon substrate even when subjected to extreme G forces. Comb finger actuators apply an electrostatic force to the proof mass in the x direction; and, when experiencing an external rotational rate around the z-axis, the Coriolis force acts along the y direction and the resulting deflection is sensed by a pair of comb-finger capacitors connected as a differential capacitive voltage divider.

Claims

1. A SOI-MEMS gyroscope, comprising:

a silicon substrate;

a proof mass;

suspension means for suspending said proof mass above said silicon substrate;

actuating means connected to said suspension means;

sensing means connected to said suspension means; and

wherein said suspension means comprises a plurality of lateral flexures and a plurality of central flexures, said central flexures being aligned with a center point of said proof mass such that said center point lies between a first pair of central flexures which are oriented to the Y axis and said center point lies between a second pair of central flexures which are oriented to the X axis.

2. A gyroscope according to claim 1, wherein:

said suspension means can suspend said proof mass above said silicon substrate even when said proof mass is subjected to 10,000 G'"'"'s of force.

3. A gyroscope according to claim 1, wherein:

each lateral flexure of said plurality of lateral flexures has plurality of lateral strips.

4. A gyroscope according to claim 3, wherein each central flexure of said plurality of central flexures has a plurality of strips.

5. A gyroscope according to claim 4, wherein said plurality of lateral flexures includes two lateral strips that are separated by a narrow channel.

6. A gyroscope according to claim 5, further comprising:

an anchor directly connected to said two lateral strips that are separated by the narrow channel.

7. A gyroscope according to claim 1, further comprising:

a plurality of flexure supports with each flexure support of said plurality of flexure supports directly connecting to a respective central flexure of said plurality of central flexures, said each flexure support directly connecting to a respective pair of lateral flexures, said respective central flexure being located between said respective pair of lateral flexures.

8. A gyroscope according to claim 7, wherein:

each central flexure has two strips of said plurality of strips that are directly connected to said flexure support.

9. A gyroscope according to claim 8, further comprising:

a strip connector directly connected to said two strips of said plurality of strips of each central flexures that connect directly to said flexure support.

10. A gyroscope according to claim 9, wherein:

said plurality of strips of each central flexure includes two additional strips that connect directly to said flexure support.

11. A gyroscope according to claim 9, wherein:

said proof mass has at least one pair of promontory regions with each respective promontory region of said at least one pair of promontory regions directly connecting to a corresponding respective lateral isthmus.

12. A gyroscope according to claim 11, wherein said plurality of strips of said plurality of central flexures includes at least one strip that connects directly to said strip connector, said at least one strip directly connecting to said corresponding respective lateral isthmus as well.

13. A gyroscope according to claim 12, wherein:

said plurality of lateral strips of each lateral flexure are all directly connected to a respective orthoganol connector.

14. A gyroscope according to claim 13, wherein:

said flexure support includes a lateral region directly connecting to an arm region of said flexure support through a connecting region;

said lateral region of said flexure support includes an isthmus that directly connects to a distinct strip of said plurality of lateral strips; and

said arm region of said flexure support includes another isthmus that directly connects to another strip of said plurality of lateral strips.

15. A SOI-MEMS gyroscope, comprising:

a proof mass;

a flexure support;

an actuator element connecting to said flexure support;

a strip connector;

a central flexure that includes said strip connector and a plurality of strips that are directly connected to said strip connector, at least one of said plurality of strips being directly connected to said flexure support and at least one strip of said plurality of strips being connected to the proof mass at a lateral isthmus location;

a lateral flexure having a plurality of lateral strips with one strip of said plurality of strips being directly connected to a lateral region of said flexure support by an isthmus and another strip of said plurality of lateral strips connecting to an arm of said flexure support by another isthmus.

16. The gyroscope of claim 15, wherein:

The actuator element is a row of a comb-finger actuator.

17. The gyroscope of claim 15, further comprising:

an anchor directly connected to two lateral strips of said plurality of lateral strips, said two lateral strips being directly connected to said anchor and being separated by a narrow channel said anchor directly connecting to an underlying silicon substrate.

18. The gyroscope of claim 15, wherein:

said gyroscope is three-fold symmetrical in that said gyroscope is symmetrical in x, in y and diagonally.

19. A gyroscope device, comprising:

a substrate surface (70);

a proof mass (52);

a plurality of central flexures (60) connecting to said proof mass, at least a portion of each central flexure of said plurality of central flexures being positioned between respective first and second promontory regions (112A, 112B) of said proof mass in one direction, and being positioned between an interior border (91) of said proof mass and a flexure support rotor (78) in another direction;

each of said plurality of central flexures having a truss (100) that is separated from said interior border by a predetermined distance, said each central flexure further including a plurality of flexure strips which are directly connected to said truss, a first flexure strip (104) of said plurality of flexure strips connects said truss (100) to said first promontory region (112A) of said proof mass and a second flexure strip (108) connects said truss to said second promontory region (112B) of said proof mass, and a third flexure strip (102) directly connects said truss (100) and said flexure support rotor (78).

20. A gyroscope device according to claim 19, wherein:

said each central flexure further comprises a fourth flexure strip (106) directly connecting said truss (100) to said flexure support rotor (78).

21. A gyroscope device according to claim 20, further comprising:

a lateral flexure (62A) connected to said flexure support rotor (78);

said flexure support rotor having a lateral region (83) and a support arm (72), said lateral flexure having a first lateral strip (94) and a second lateral strip (96), said first lateral strip being directly connected to an orthoganol truss (99) and to said arm region (72) of said flexure support rotor (78), said second lateral strip (96) being directly connected to said orthoganol truss (99) and to said lateral region (83) of said flexure support rotor (78), said first lateral strip making direct contact with said arm region at an isthmus strip location (74) and said second lateral strip making direct contact with said lateral region (83) at a second isthmus strip location (76), said first and second isthmus strip locations being the only locations where said lateral flexure makes direct contact with said flexure support rotor (78).

22. A gyroscope device according to claim 21, wherein:

a first lateral isthmus (69A) directly connects said first flexure strip (104) to said first promontory region (112A) and a second lateral isthmus (69B) directly connects said second flexure strip (108) to said second promontory region (112B).

23. A gyroscope device according to claim 21, wherein:

said lateral flexure further comprises a first narrow strip (88) and a second narrow strip (92) that are both directly connected to said orthoganol truss (99).

24. A gyroscope device according to claim 23, wherein:

a narrow channel (90) separates said first narrow strip and said second narrow strip, said first narrow strip and said second narrow strip connecting to an anchor that connects to said substrate surface.

25. A gyroscope device according to claim 24, wherein:

said proof mass measures 1770 μ

m across.

26. A gyroscope according to claim 24, wherein:

said proof mass has a side border region (110A) in parallel with at least a portion of said support arm of said flexure support rotor.

27. A gyroscope device according to claim 19, further comprising:

a lateral flexure (62A) connected to said flexure support rotor (78);

said flexure support rotor having a lateral region (83) and a support arm (72), said lateral flexure having a first lateral strip (94) and a second lateral strip (96), said first lateral strip being directly connected to an orthoganol truss (99) and to said support arm (72) of said flexure support rotor (78), said second lateral strip (96) being directly connected to said orthoganol truss (99) and to said lateral region (83) of said flexure support rotor (78), said first lateral strip making direct contact with said arm region at an isthmus strip location (74) and said second lateral strip making direct contact with said lateral region (83) at a second isthmus strip location (76), said first and second isthmus strip locations being the only locations where said lateral flexure makes direct contact with said flexure support rotor (78).

28. A gyroscope device according to claim 19, wherein:

a first lateral isthmus (69A) directly connects said first flexure strip (104) to said first promontory region (112A) and a second lateral isthmus (69B) directly connects said second flexure strip (108) to said second promontory region (112B).