Planar inertial measurement units based on gyros and accelerometers with a common structure

• US 6,859,751 B2
• Filed: 12/17/2002
• Issued: 02/22/2005
• Est. Priority Date: 12/17/2001
• Status: Expired due to Fees

• Current Assignee: Milli Sensor Systems & Actuators, Inc.
• Original Assignee: Milli Sensor Systems & Actuators, Inc.
• Inventors: Cardarelli, Donato
• Primary Examiner(s): Barlow, John
• Assistant Examiner(s): Walling, Meagan S
• Application Number:
  US10/321,774
• Publication Number:
  US 20030216884A1
• Time in Patent Office: 798 Days
• Field of Search: 702/141, 702/145, 735/040.2, 735/040.3, 735/040.4, 735/04, 73/12
• US Class Current: 702/141
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis
• CPC Class Codes: G01C 21/166 Mechanical, construction or arrangement details of inertial navigation systems
• CPC Class Codes: G01C 21/183 Compensation of inertial measurements, e.g. for temperature effects
• CPC Class Codes: G01P 15/18 in two or more dimensions

Abstract

Inertial Measurement Units based on integrated designs to reduce alignment and assembly costs. Integration also leads to performance improvement, increased miniaturization and simplification as well as reduced cost. Also disclosed are gyroscopes and accelerometers that are identical, yet by their mechanization, can be made to act as separate sensors. Miniaturization and simplification is improved by combining instruments that can share a common member. Savings in space and complexity are also possible in the electronics when elements are shared.

Claims

1. A planar, integrated inertial measurement unit (IMU) comprising a plurality of inertial measurement instruments that are based on a common structure, the IMU comprising:

at least two coplanar inertial measurement instruments, each instrument comprising;

a case;

a planar outer member coupled to the case by flexures, and that is driven angularly to oscillate about a drive axis with respect to the case; and

a planar inner member coplanar with the outer member and coupled to the outer member by flexures, and that rotates about an output axis that is orthogonal to the drive axis in response to the acceleration or rotation rate of the IMU.

2. The planar IMU of claim 1 comprising a six degree of freedom (DOF) IMU.

3. The planar IMU of claim 2 comprising at least two gyroscopes and at least five accelerometers, all inertial measurement instruments being coplanar.

4. The planar IMU of claim 3 wherein two accelerometers are arranged to sense accelerations along a first axis in the plane of the IMU.

5. The planar IMU of claim 4 wherein two different accelerometers are arranged to sense accelerations along a second axis in the plane of the IMU and orthogonal to the first axis.

6. The planar IMU of claim 5 wherein the four accelerometers are arranged in the IMU such that their inner members are at equal radial distances from the center of the IMU, and arranged such that as a group they measure both centrifugal and linear accelerations.

7. The planar IMU of claim 5 wherein the four accelerometers are arranged in the IMU such that their inner members are at equal radial distances from the center of the IMU, and are arranged such that as a group they measure both angular and linear accelerations.

8. The planar IMU of claim 3 wherein an accelerometer is arranged to sense accelerations along a third axis that is orthogonal to the plane of the IMU.

9. The planar IMU of claim 1 wherein the outer member of two inertial measurement instruments is common, to form a multi-instrument set including two inertial measurement instruments.

10. The planar IMU of claim 9 comprising four multi-instrument sets, each such set comprising two inertial measurement instruments with a common outer member.

11. The planar IMU of claim 10 wherein three multi-instrument sets each comprise one gyroscope and one accelerometer, and one set comprises two accelerometers.

12. The planar IMU of claim 11 further comprising a common drive for the outer members of each of the sets of instruments.

13. The planar IMU of claim 11 wherein two accelerometers are arranged to sense accelerations along a first axis in the plane of the IMU.

14. The planar IMU of claim 13 wherein two different accelerometers are arranged to sense accelerations along a second axis in the plane of the IMU and orthogonal to the first axis.

15. The planar IMU of claim 11 wherein an accelerometer is arranged to sense accelerations along an axis that is orthogonal to the plane of the IMU.

16. The planar IMU of claim 1 comprising two coplanar instruments, one a gyroscope and one an accelerometer.

17. The planar IMU of claim 16 wherein the gyroscope inner member is adapted to oscillate angularly in the plane about an axis that is normal to the plane.

18. The planar IMU of claim 16 wherein the accelerometer inner member is adapted to rotate about an axis that is normal to the plane.

19. The planar IMU of claim 1 comprising two coplanar instruments, both accelerometers.

20. The planar IMU of claim 19 wherein the inner members of one accelerometer is adapted to rotate about an axis that lies in the plane of the IMU, and the inner member of the other accelerometer is adapted to rotate about an axis that is orthogonal to the plane.

21. A planar, integrated gyroscope inertial measurement instrument, comprising:

a planar case;

a planar outer member coplanar with the case and coupled to the case by flexures, and that is driven with respect to the case by integral capacitive comb drives;

a planar inner member coplanar with the outer member and coupled to the outer member by flexures, and that moves with respect to the outer member in response to the rotation rate of the gyroscope; and

comb interleaved pickoffs defined in part on the outer member and in part on the inner member, for detecting motion of the inner member relative to the outer member.

22. The gyroscope inertial measurement instrument of claim 21 wherein the outer member is driven to oscillate about an axis that lies in the plane.

23. The gyroscope inertial measurement instrument of claim 21 wherein the outer member is driven to oscillate about an axis that is orthogonal to the plane.

24. The planar gyroscope of claim 21, further comprising electrical isolation spacers that enable independent operation of the drives and pickoffs.

25. A planar, integrated inertial measurement unit (IMU) based on a common structure and comprising a plurality of inertial measurement instruments, the IMU comprising:

at least seven separate inertial measurement instruments, each inertial measurement instrument having a driven member and a sense member, wherein the sense members of all such inertial measurement instruments are separate from one another, the instruments comprising at least two planar gyroscopes and at least five planar accelerometers, all arranged about the center of the IMU;

wherein four of the accelerometers are arranged in the IMU such that their sense members are at equal radial distances from the center of the IMU, and arranged such that as a group they measure both centrifugal and linear accelerations.

26. A planar, integrated inertial measurement unit (IMU) based on a common structure and comprising a plurality of inertial measurement instruments, the IMU comprising:

at least seven separate inertial measurement instruments, each inertial measurement instrument having a driven member and a sense member, wherein the sense members of all such inertial measurement instruments are separate from one another, the instruments comprising at least two planar gyroscopes and at least five planar accelerometers, all arranged about the center of the IMU;

wherein four of the accelerometers are arranged in the IMU such that their sense members are at equal radial distances from the center of the IMU, and are arranged such that as a group they measure both angular and linear accelerations.

27. A planar, integrated inertial measurement unit multisensor, comprising:

a case;

a planar outer member coupled to the case by flexures, and that is rotationally oscillated with respect to the case in and out of the plane about a drive axis in the plane;

a planar inner member coplanar with the outer member and coupled to the outer member by a plurality of flexures, and that oscillates rotationally in the plane about an axis that is normal to the plane in response to rotation rate of the IMU multisensor; and

a pendulous mass carried by the inner member and located along the drive axis, wherein the pendulous mass rotates about an axis that is normal to the plane in response to acceleration.

28. A planar, integrated inertial measurement unit (IMU) comprising a plurality of inertial measurement instruments that are based on a common structure, the IMU comprising:

a plurality of physically separate, coplanar inertial measurement instruments, each instrument comprising;

a case;

a planar outer member coupled to the case by flexures, and that is driven angularly to oscillate about a drive axis with respect to the case; and

a planar inner member coplanar with the outer member and coupled to the outer member by flexures, and that rotates about an output axis that is orthogonal to the drive axis in response to the acceleration or rotation rate of the IMU; and

a common support substrate supporting each of the inertial measurement instruments.

29. The planar IMU of claim 28 made by a transfer process, in which the instruments are fabricated together on one surface of an instrument substrate, the instrument substrate surface is bonded to the common support substrate, and portions of the instrument substrate are removed, to leave behind the instruments.

30. A planar, integrated inertial measurement unit (IMU) comprising a plurality of inertial measurement instruments that are based on a common structure, the IMU comprising:

at least two coplanar inertial measurement instruments, each instrument comprising;

a case;

a planar outer member coupled to the case by flexures, and that is driven with respect to the case; and

a planar inner member coplanar with the outer member and coupled to the outer member by flexures, and that rotates in response to the acceleration or rotation rate of the IMU;

wherein the outer member of at least two said coplanar inertial measurement units is common.

31. The planar IMU of claim 30 comprising a six degree of freedom (DOF) IMU.

32. The planar IMU of claim 31 comprising at least two gyroscopes and at least five accelerometers, all inertial measurement instruments being coplanar.

33. The planar IMU of claim 32 wherein two accelerometers are arranged to sense accelerations along a first axis in the plane of the IMU.

34. The planar IMU of claim 33 wherein two different accelerometers are arranged to sense accelerations along a second axis in the plane of the IMU and orthogonal to the first axis.

35. The planar IMU of claim 34 wherein a fifth accelerometer is arranged to sense accelerations along a third axis that is orthogonal to the plane of the IMU.

36. The planar IMU of claim 34 wherein the four accelerometers are arranged in the IMU such that their inner members are at equal radial distances from the center of the IMU, and arranged such that as a group they measure both centrifugal and linear accelerations.

37. The planar IMU of claim 34 wherein the four accelerometers are arranged in the IMU such that their inner members are at equal radial distances from the center of the IMU, and are arranged such that as a group they measure both angular and linear accelerations.

38. The planar IMU of claim 30 wherein the outer member of two inertial measurement instruments is common, to form a multi-instrument set including two inertial measurement instruments.

39. The planar IMU of claim 38 comprising four multi-instrument sets, each such set comprising two inertial measurement instruments with a common outer member.

40. The planar IMU of claim 39 wherein three multi-instrument sets each comprise one gyroscope and one accelerometer, and one set comprises two accelerometers.

41. The planar IMU of claim 40 wherein two accelerometers are arranged to sense accelerations along a first axis in the plane of the IMU.

42. The planar IMU of claim 41 wherein two different accelerometers are arranged to sense accelerations along a second axis in the plane of the IMU and orthogonal to the first axis.

43. The planar IMU of claim 40 wherein an accelerometer is arranged to sense accelerations along an axis that is orthogonal to the plane of the IMU.

44. The planar IMU of claim 40 further comprising a common drive for the outer members of each of the sets of instruments.

45. The planar IMU of claim 30 comprising two coplanar instruments, one a gyroscope and one an accelerometer.

46. The planar IMU of claim 45 wherein the gyroscope inner member is adapted to oscillate angularly in the plane about an axis that is normal to the plane.

47. The planar IMU of claim 45 wherein the accelerometer inner member is adapted to rotate about an axis that is normal to the plane.

48. The planar IMU of claim 30 comprising two coplanar instruments, both accelerometers.

49. The planar IMU of claim 48 wherein the inner member of one accelerometer is adapted to rotate about an axis that lies in the plane of the IMU, and the inner member of the other accelerometer is adapted to rotate about an axis that is orthogonal to the plane.