Micromechanical gyroscopic transducer with improved drive and sense capabilities

• US 5,408,877 A
• Filed: 03/16/1992
• Issued: 04/25/1995
• Est. Priority Date: 03/16/1992
• Status: Expired due to Term

• Current Assignee: Charles Stark Draper Laboratory Incorporated
• Original Assignee: Charles Stark Draper Laboratory Incorporated
• Inventors: Greiff, Paul, Boxenhorn, Burton
• Primary Examiner(s): Williams, Hezron E.
• Assistant Examiner(s): Oda, Christine K.
• Application Number:
  US07/851,913
• Time in Patent Office: 1,135 Days
• Field of Search: 73/505, 73/517 AV, 73/517 R, 73/517 B, 73/518, 310/329
• US Class Current: 73/504.12
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis

Abstract

A double gimbal micromachined gyroscopic transducer is provided in a substrate having a pit extending downwardly from a top surface of the substrate. A gyroscopic transducer element suspended above the pit comprises an outer sense gimbal plate integral with the substrate, coupled to the substrate by a pair of flexible elements attached to opposite ends of the plate. The flexible elements are axially aligned to permit oscillatory motion about a sense axis passing through the flexible elements. The gyroscopic transducer further includes an inner drive gimbal plate integral with and interior to the sense gimbal plate. The drive gimbal plate is coupled to the sense gimbal plate by a second pair of flexible elements along an axis orthogonal to the first pair of flexible elements. The drive gimbal plate also includes a balanced mass generally centrally located on the drive gimbal plate. Also included are drive and sense electronics, for energizing the drive gimbal plate to oscillate about the drive axis, and for sensing any movement of the sense gimbal plate indicative of an angular rate about an input axis. The sense electronics includes a sense electrode disposed so as not to be in close proximity to and interfere with free oscillatory motion of the drive gimbal plate.

Claims

1. A dual gimbal micromachined gyroscopic transducer comprising:

a substrate including a pit having a bottom region, said pit extending downwardly from a top surface of said substrate;

a gyroscopic transducer element suspended above the bottom region of said pit, said gyroscopic transducer element comprising;

a sense gimbal plate integral with said substrate, said sense gimbal plate coupled to said substrate by first and second flexible elements, a first end of each of said first and second flexible elements coupled to opposite ends of said sense gimbal plate, and a second end of each of said first and second flexible elements coupled to said substrate, said first and second flexible elements axially aligned to permit oscillatory motion about a sense axis which passes through said first and second flexible elements;

a drive gimbal plate integral with and interior to said sense gimbal plate, said drive gimbal plate coupled to said sense gimbal plate by third and fourth flexible elements, a first end of each of said third and fourth flexible elements coupled to opposite ends of said drive gimbal plate, and a second end of each of said third and fourth flexible elements coupled to said sense gimbal plate, said third and fourth flexible elements axially aligned to permit oscillatory motion about a drive axis which passes through said third and fourth flexible elements, said drive axis disposed orthogonal to said sense axis, said drive gimbal plate further including a balanced mass generally centrally located on said drive gimbal plate;

means for oscillating said drive gimbal plate including at least one drive electrode, coupled to means for energizing said drive electrode, said at least one drive electrode disposed in spaced relationship to at least a portion of said drive gimbal plate, said means for energizing said at least one drive electrode operative for causing said drive gimbal plate to oscillate about said drive axis; and

means for sensing rotation of said sense gimbal plate, said means for sensing including at least one sense electrode, coupled to said means for sensing rotation of said sense gimbal plate, said at least one sense electrode disposed in spaced relationship to at least a portion of said sense gimbal plate, said at least one sense electrode disposed so as not to be in close proximity to, and interfere with free oscillatory motion of said drive gimbal plate, said means for sensing and said at least one sense electrode operative for sensing rotation of said sense gimbal plate about said sense axis, said means for sensing for providing an indication of angular rotation detected by said gyroscopic transducer about an input axis orthogonal to said drive and sense axes.

2. The gyroscopic transducer of claim 1 wherein said at least one drive electrode includes a buried electrode integral with said bottom region of said pit.

3. The gyroscopic transducer of claim 1 wherein said at least one sense electrode includes at least one buried electrode integral with said bottom region of said pit.

4. The gyroscopic transducer of claim 1 wherein said substrate includes a semiconductor material;

and

wherein said drive and sense gimbal plates, and said first, second, third and fourth flexible elements are doped to resist selective etching.

5. The gyroscopic transducer of claim 4

wherein said pit, said drive and sense gimbal plates, and said first, second, third and fourth flexible elements are defined from said semiconductor material utilizing selective etching.

6. The gyroscopic transducer of claim 1 wherein said means for oscillating said drive gimbal plate causes said drive gimbal plate to oscillate at the resonant frequency of the drive gimbal plate.

7. A dual gimbal micromachined gyroscopic transducer comprising:

a substrate including a pit having a bottom region, said pit extending downwardly from a top surface of said substrate;

a gyroscopic transducer element suspended above the bottom region of said pit, said gyroscopic transducer element comprising;

a sense gimbal plate integral with said substrate, said sense gimbal plate coupled to said substrate by first and second flexible elements, a first end of each of said first and second flexible elements Coupled to opposite ends of said sense gimbal plate, and a second end of each of said first and second flexible elements coupled to said substrate, said first and second flexible elements axially aligned to permit oscillatory motion about a sense axis which passes through said first and second flexible elements;

a drive gimbal plate integral with and interior to said sense gimbal plate, said drive gimbal plate coupled to said sense gimbal plate by third and fourth flexible elements, a first end of each of said third and fourth flexible elements coupled to opposite ends of said drive gimbal plate, and a second end of each of said third and fourth flexible elements coupled to said sense gimbal plate, said third and fourth flexible elements axially aligned to permit oscillatory motion about a drive axis which passes through said third and fourth flexible elements, said drive axis disposed orthogonal to said sense axis, said drive gimbal plate further including a balanced mass generally centrally located on said drive gimbal plate;

means for oscillating said drive gimbal plate including at least one drive electrode, coupled to means for energizing said drive electrode, said at least one drive electrode disposed in spaced relationship to at least a portion of said drive gimbal plate, said means for energizing said at least one drive electrode operative for causing said drive gimbal plate to oscillate about said drive axis; and

means for sensing rotation of said sense gimbal plate, said means for sensing including at least one sense electrode, coupled to said means for sensing rotation of said sense gimbal plate, said at least one sense electrode disposed in spaced relationship to at least a portion of said sense gimbal plate, said at least one sense electrode disposed so as not to be in close proximity to, and interfere with free oscillatory motion of said drive gimbal plate, said means for sensing and said at least one sense electrode operative for sensing rotation of said sense gimbal plate about said sense axis, said means for sensing for providing an indication of angular rotation detected by said gyroscopic transducer about an input axis orthogonal to said drive and sense axes,

wherein said at least one sense electrode includes at least one bridge sense electrode; and

wherein said at least one bridge sense electrode is disposed parallel to said sense gimbal plate and to said sense axis, for preventing interference with the oscillation of said drive gimbal plate about said drive axis by said at least one bridge sense electrode.

8. The gyroscopic transducer of claim 7 wherein said at least one bridge sense electrode disposed in spaced relationship to at least a portion of said sense gimbal plate is disposed a predetermined distance in the range of 2 to 5 microns from said sense gimbal plate.