Planar inertial sensor

• US 4,598,585 A
• Filed: 03/19/1984
• Issued: 07/08/1986
• Est. Priority Date: 03/19/1984
• Status: Expired due to Term

• Current Assignee: Charles Stark Draper Laboratory Incorporated
• Original Assignee: Charles Stark Draper Laboratory Incorporated
• Inventors: Boxenhorn, Burton
• Primary Examiner(s): Kreitman, Stephen A.
• Application Number:
  US06/591,007
• Time in Patent Office: 841 Days
• Field of Search: 73/505, 73/517 R, 73/517 AY, 73/518, 338/47, 338/43, 338/46, 310/329, 310/330, 310/338
• US Class Current: 73/504.12
• CPC Class Codes: G01C 19/5712 the devices involving a micromechanical structure
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis
• CPC Class Codes: G01P 15/0888 for indicating angular acceleration
• CPC Class Codes: G01P 15/097 by vibratory elements
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 2015/0831 the mass being of the paddle type having the pivot axis between the longitudinal ends of the mass, e.g. see-saw configuration

Abstract

A planar inertial sensor includes a sheet member having one inner planar element adapted for limited angular motion about a (Y) axis perpendicular to an input (Z) axis. In a gyroscope form, the inner planar element is also adapted for limited angular motion about an (X) axis normal to and intersecting with the Y axis. The gyroscope form includes an outer driving planar element which is continuously driven in an oscillatory manner in limited excursions about the Y axis. The driving element is coupled to the inner element so that oscillatory motion of the driving element is coupled to the inner element. Position sensors provide signals representative of the angular position of the inner element relative to the X axis, which in turn are representative of angular rates impressed on the sensor about the input (Z) axis which is orthogonal to the X and Y axes. In an accelerometer form, the inner planar element is characterized by a mass imbalance across the Y axis. Position sensors provide signals representative of the angular position of the inner element, which in turn are representative of the acceleration of the sensor in the direction of the input (Z) axis.

Claims

1. A planar inertial sensor having an input (Z) axis, comprising a sheet member and associated base member, said base member including means for supporting the peripheral region of said sheet member in a plane perpendicular to said input (Z) axis, said plane including a first (X) reference axis and a second (Y) reference axis, said first and second reference axes being mutually perpendicular and intersecting said input axis at a common point,

wherein said sheet member encloses a first pair of opposed C-shaped void regions and said first pair of void regions being disposed symmetrically about said second axis and said common point,

wherein the portions of said sheet member between the opposed ends of the void regions of said first pair and the portions of said sheet member interior to said first pair of void regions are spaced apart in the direction of said Y axis from said base member, and

wherein the portions of said sheet member between the opposed ends of said void regions of said first pair are flexible, whereby said common point is constrained to be substantially in said plane, and further comprising means for sensing inertial changes in position of said support means.

2. A planar inertial sensor according to claim 1 further comprising:

(A) at least one second pair of opposed C-shaped void regions, the void regions of said first pair being larger than the void regions of said second pairs, and

(B) said second pair of void regions being interior to the void regions of said first pair and being disposed symmetrically about axes parallel to said first axis when said sheet member lies in said plane.

3. A planar inertial sensor according to claim 2 including a single second pair of opposed C-shaped void regions, said single second pair being disposed about said common point wherein the portion of said sheet member interior to said second pair of void regions includes an inner element axis perpendicular to said Y axis and passing through said common point.

4. A planar inertial sensor according to claim 3 further comprising:

means for generating a signal representative of the angular displacement of the portion of said sheet member interior to said second pair of void regions about said first reference axis, said signal being representative of the angular rate of said sensor about said input axis.

5. A planar inertial sensor according to claim 4 wherein said generating means includes a first sensing planar conductive region on the surface of the portion of said sheet member interior to said second pair of void regions and on one side of said inner element axis, said first sensing planar conductive region being adapted to oppose a first sensing planar conductive element fixed with respect to said base member, said first sensing planar conductive region and said first sensing planar conductive element forming a position transducer having a characteristic capacitance representative of the angular orientation of said portion of said sheet member interior to said second pair of void regions about said first reference axis.

6. A planar inertial sensor according to claim 5 wherein said generating means further includes a second sensing planar conductive region on the surface of the portion of said sheet member interior to said second pair of void regions and on the other side of said inner element axis, said second sensing planar conductive region being adapted to oppose a second sensing planar conductive element fixed with respect to said base member, said second sensing planar conductive region and said second sensing planar conductive element forming a position transducer having sensing a characteristic capacitance representative of the angular orientation of said portions of said sheet member interior to said second pair of void regions about said first reference axis.

7. A planar inertial sensor according to claims 3 further comprising:

driving means for driving the portion of said sheet member between said first and second pairs of void regions in an oscillatory motion about said second axis.

8. A planar inertial sensor according to claim 7 wherein said driving means includes a first driving planar conductive region on the surface of the portion of said sheet member between said first and second pairs of void regions and on one side of said second reference axis, and a second driving planar conductive regions on the surface of the portion of said sheet member between said first and second pairs of void regions and on the other side of said second reference axis, said first and second driving planar conductive regions being adapted to oppose first and second driving planar conductive elements, respectively, fixed with respect to said base member.

9. A planar inertial sensor according to claim 8 wherein said driving means further includes means for applying a first periodic voltage signal across said first driving planar conductive region and said first driving planar conductive element, and means for applying a second periodic voltage signal across said second driving planar conductive region and said second driving planar conductive element, said first and second voltage signals having the same fundamental frequency and a non-zero d.c. component, and said first voltage signal being shifted in phase by 180 degrees with respect to said second voltage signal.

10. A planar inertial sensor according to claim 4 further comprising:

driving means for driving the portion of said sheet member between said first and second pairs of void regions in an oscillatory motion about said second axis.

11. A planar inertial sensor according to claim 2 including a plurality of second pairs of opposed, C-shaped void regions, each of said second pairs being disposed symmetrically about an associated central point along said Y axis, wherein the portions of said sheet member interior to said second pairs of void regions each include an inner element axis perpendicular to said Y axis and passing through a central point associated with said inner element.

12. A planar inertial sensor according to claim 11 further comprising:

means for generating a signal representative of the angular displacement of the portion of said sheet member interior to said second pair of void regions about said first reference axis, said signal being representative of the angular rate of said gyroscope about said input axis.

13. A planar inertial sensor according to claim 12 wherein said generating means includes a first sensing planar conductive region on the surface of the portion of said sheet member interior to each of said second pairs of void regions and on one side of its respective inner element axis, each of said first sensing planar conductive regions being adapted to oppose a first sensing planar conductive element fixed with respect to said base member, said first sensing planar conductive regions and said first sensing planar conductive elements forming position transducers having a characteristic capacitance representative of the angular orientation of said portions of said sheet member interior to said second pairs of void regions about said first reference axis.

14. A planar inertial sensor according to claim 13 wherein said generating means further includes a second sensing planar conductive region on the surface of the portion of said sheet member within each of said second pairs of void regions and on the other side of its inner element axis, said second sensing planar conductive regions being adapted to oppose second sensing planar conductive elements fixed with respect to said base member, said second sensing planar conductive regions and said second sensing planar conductive elements forming a position transducer having sensing a characteristic capacitance representative of the angular orientation of said portions of said sheet member within said second pair of void regions about said first reference axis.

15. A planar inertial sensor according to claim 12 further comprising:

driving means for driving the portion of said sheet member between said first and second pairs of void regions in an oscillatory motion about said second axis.

16. A planar inertial sensor according to claim 11 further comprising:

driving means for driving the portion of said sheet member between said first and second pairs of void regions in an oscillatory motion about said second axis.

17. A planar inertial sensor according to claim 16 wherein said driving means includes a first driving planar conductive region on the surface of the portion of said sheet member between said first and second pairs of void regions and on one side of said second reference axis, and a second driving planar conductive regions on the surface of the portion of said sheet member between said first and second pairs of void regions and on the other side of said second reference axis, said first and second driving planar conductive regions being adapted to oppose first and second driving planar conductive elements, respectively, fixed with respect to said base member.

18. A planar inertial sensor according to claim 17 wherein said driving means further includes means for applying a first periodic voltage signal across said first driving planar conductive region and said first driving planar conductive element, and means for applying a second periodic voltage signal across said second driving planar conductive region and said second driving planar conductive element, said first and second voltage signals having the same fundamental frequency and a non-zero d.c. component, said first voltage signal being shifted in phase by 180 degrees with respect to such second voltage signal.

19. A planar inertial sensor according to claim 1 or 10 or 15 wherein said sheet member and associated base member are constructed from an integral material.

20. A planar inertial sensor according to claim 19 wherein said integral material is a semiconductor wafer, said sheet member being a dielectric layer and said base member being silicon, said sheet member overlying said base member.

21. A planar inertial sensor according to claim 20, wherein said dielectric layer is a material from the group consisting of SiO₂, Si₂ N₄, and (SiO₂)_x (Si₃ N₄)_y.

22. A planar inertial sensor according to claim 19 further comprising associated electrical control circuitry integrated with said silicon wafer.

23. A planar inertial sensor according to claim 19 wherein said base member includes a portion underlying said sheet member and wherein the portions of said sheet member between the opposed ends of the void regions of said first pair and the portions of said sheet member interior to said first pair of void regions are spaced apart in the direction of said Y axis from said base member.

24. A planar inertial sensor according to claim 1 wherein the portion of said sheet member between the ends of said void regions of said first pair is imbalanced across said second axis.

25. A planar inertial sensor according to claim 24 further comprising:

means for generating a signal representative of the angular displacement of the portion of said sheet member interior to said first pair of void regions about said second reference axis, said signal being representative of the acceleration of said sensor in the direction of said input axis.

26. A planar inertial sensor according to claim 25 wherein said sheet member and associated base member are constructed from an integral material.

27. A planar inertial sensor according to claim 26 wherein said integral material is a semiconductor wafer, said sheet member being a dielectric layer and said base member being silicon, said sheet member overlying said base member.

28. A planar inertial sensor according to claim 27, wherein said dielectric layer is a material from the group consisting of SiO₂, Si₂ N₄, and (SiO₂)_x (Si₃ N₄)_y.

29. A planar inertial sensor according to claim 26 further comprising associated electrical control circuitry integrated with said silicon wafer.

30. A planar inertial sensor according to claim 26 wherein said base member includes a portion underlying said sheet member and wherein the portions of said sheet member between the opposed ends of the void regions of said first pair and the portions of said sheet member interior to said first pair of void regions are spaced apart in the direction of said Y axis from said base member.