Solid state vibrating gyro

• US 4,884,446 A
• Filed: 10/17/1988
• Issued: 12/05/1989
• Est. Priority Date: 03/12/1987
• Status: Expired due to Fees

• Current Assignee: Per B. Ljung
• Original Assignee: Per B. Ljung
• Inventors: Ljung, Per B.
• Primary Examiner(s): Chapman, John
• Application Number:
  US07/259,483
• Time in Patent Office: 414 Days
• Field of Search: 73/505
• US Class Current: 73/504.12
• CPC Class Codes: G01C 19/5642 using vibrating bars or beams

Abstract

An angular rate sensor is formed of a transducer and associated electronics. The transducer consists of two parallel beams with attached proof masses, which are angularly vibrated about respective proof masses center of gravity in a first plane. Rotation of the gyro about its input axis results in Coriolis moments causing vibration in a plane normal to the first plane. A torque is applied to restrain the vibration of the proof masses to the first plane. A voltage proportional to this torque is demodulated and filtered and output as a voltage proportional to the angular input rate.

Claims

1. An angular rate sensor comprising:

(a) an elastic element having high axial, radial and torsional stiffness including;

(i) two elastic beams; and

(ii) a common support joining the two elastic beams;

(b) two inertia members balanced such that their respective centers of gravity would remain static when the inertia members are angularly vibrated;

(c) means for angularly vibrating the inertia members in a first plane such that the inertia members have respective angular vibrational nodal points coinciding with their corresponding centers of gravity;

wherein each of the inertia members is respectively tightly coupled to a free end of corresponding one of the elastic beams such that the inertia members are not supported at their respective vibrational nodal points so that when at least one of the inertia members is angularly vibrated about its center of gravity, no substantial vibrational energy is lost since the inertial members are not supported at their respective vibrational nodal points and a high Q-value is thereby generated.

2. The angular rate sensor of claim 1, wherein, due to the tight coupling of the elastic beams to the corresponding interial members, the means for angularly vibrating the inertia members further causes the elastic beams to be evenly stressed along their respective entire lengths.

3. The angular rate sensor of claim 1, further comprising:

means for restraining angular vibrations of the inertia members in a second plane.

4. The angular rate sensor of claim 1, further comprising:

means for sensing angular vibrations of the inertia members in first and second planes.

5. The angular rate sensor of claim 1, further comprising:

means for restraining angular vibrations of the inertia members in a second plane;

means for sensing angular vibrations of the inertia members in the first and second planes;

wherein the vibrating, restraining and sensing means are located coplanarly.

6. The angular rate sensor of claim 1, wherein the elastic elements are made of a monocrystalline material.

7. The angular rate sensor of claim 5, wherein the inertia members have resonant frequencies f₁ and f₂ in the first and second planes

where ##EQU2## wherein said elastic beams are dimensioned such that the respective spring ranges are proportional to the respective inertias of the inertia members, thereby causing f₁ to be substantially identical to f₂.

8. The angular rate sensor of claim 1, wherein each of the inertia members comprises two rectangular cross-sectional members.

9. The angular rate sensor of claim 1, wherein the elastic beams and common support of the elastic elements are cross-sectionally rectangular shaped.

10. The angular rate sensor of claim 5, wherein the vibrating, restraining and sensing means comprise electrostatic elements.

11. The angular rate sensor of claim 5, wherein the vibrating means, the restraining means and the sensing means respectively comprise cross-coupled electrostatic elements;

and

wherein the vibrating, restraining and sensing means are insensitive to linear vibrations of the inertia members by virtue of being cross-coupled.

12. An angular rate sensor comprising:

two inertia members each having an elastic element and two arms connected to a free end of the elastic element and integrally extending in parallel from a body, the inertia members having corresponding centers of gravity;

means for angularly vibrating the inertial members in a first plane such that the inertial members have respective angular vibrational nodal points coinciding with their respective centers of gravity;

a support tightly coupling the respective elastic elements of the inertia members so that the inertia members are not supported at their respective vibrational nodal points and that vibrations received by one of the inertia members is transmitted to the other inertia member;

wherein, when at least one of the inertia members is angularly stressed, no substantially vibrational energy is lost and a high Q-value is thereby generated.

13. The angular rate sensor of claim 12, further comprising:

means for restraining angular vibrations of the inertia members in a second plane;

means for sensing angular vibrations of the inertia members in the first and second planes;

wherein the vibrating, restraining and sensing means are located coplanarly.

14. The angular rate sensor of claim 13, wherein the inertia members have resonant frequencies f₁ and f₂ in the first and second planes

where ##EQU3## wherein said elastic elements are elastic beams dimensioned such that the respective spring rates are proportional to the respective inertias of the inertia members, thereby causing f₁ to be substantially identical to f₂.

15. The angular rate sensor of claim 13, wherein the vibrating, restraining and sensing means comprise electrostatic elements.

16. The angular rate sensor of claim 13, wherein the vibrating means, the restraining means and the sensing means respectively comprise cross-coupled electrostatic elements;

and

wherein the vibrating, restraining and sensing means are insensitive to linear vibrations of the inertia members by virtue of being cross-coupled.

17. The angular rate sensor of claim 12, wherein the inertia members are made of a monocrystalline material.