Solid state orientation sensor with 360 degree measurement capability

• US 20060265178A1
• Filed: 07/25/2006
• Published: 11/23/2006
• Est. Priority Date: 12/09/1998
• Status: Active Grant

• Current Assignee: Lord Corporation (Parker-Hannifin Corporation)
• Original Assignee: MicroStrain, Inc. (Spectris PLC)
• Inventors: Arms, Steven W., Townsend, Christopher P.
• Granted Patent: US 7,433,798 B2
• Time in Patent Office: Days
• US Class Current: 702/153
• CPC Class Codes: G01C 17/30 Earth-inductor compasses
• CPC Class Codes: G01C 21/08 involving use of the magnetic field of the earth

Abstract

A miniature, self-contained solid state orientation sensor is described. One aspect is a solid state inclinometer sensor system, comprising a digital network of devices. Each device of the network includes a solid state inclinometer attached to a mounting structure. The inclinometer includes gravity sensors and a processor. The gravity sensors are mounted to provide components of earth'"'"'s gravity. The processor uses data derived from the gravity sensors to calculate inclination of the mounting structure and provide a digital output for transmission on the digital network. Each device can use three magnetometers and three accelerometers to calculate pitch, roll, and yaw (compass heading) angles relative to the earth'"'"'s magnetic and gravitational fields. The three orientation angles can be output in digital RS232 or optional multi-drop RS485. The device can also be programmed to provide raw accelerometer and magnetometer data in true physical units. The device is capable of measuring angles from 0 to 360 degrees on the yaw axis, 0 to 360 degrees on the pitch axis, and −70 to +70 degrees on the roll axis. The yaw output can be compensated for errors due to pitch and roll using embedded algorithms. Applications include fast solid state compassing, robotics, virtual reality, down-hole well drilling, and body position tracking for biomedical and multimedia applications.

Claims

1. A solid state inclinometer sensor system, comprising a digital network of devices, wherein each device of said network includes a solid state inclinometer attached to a mounting structure, wherein said inclinometer includes gravity sensors and a processor, wherein said gravity sensors are mounted to provide components of earth'"'"'s gravity, wherein said processor uses data derived from said gravity sensors to calculate inclination of said mounting structure and provide a digital output for transmission on said digital network.

2. A solid state inclinometer sensor system as recited in claim 1, further comprising analog filtering.

3. A solid state inclinometer sensor system as recited in claim 1, further comprising digital filtering.

4. A solid state inclinometer sensor system, as recited in claim 3, wherein said filter comprises a programmable infinite impulse response filter.

5. A solid state inclinometer sensor system as recited in claim 3, further comprising two digital filters with different cutoff frequencies.

6. A solid state inclinometer sensor system as recited in claim 5, wherein said processor is connected for monitoring output of said digital filters and for determining which digital filter to apply.

7. A solid state inclinometer sensor system as recited in claim 3, wherein said digital filter includes a programmable digital filter, wherein a parameter of said digital filter is set by a characteristic of data coming from said inclinometer.

8. A solid state inclinometer sensor system as recited in claim 1, wherein each said device further comprises a plurality of magnetic field sensors connected so data derived from said magnetic field sensors is processed in said processor.

9. A solid state inclinometer sensor system, as recited in claim 8, wherein said magnetic field sensors comprise solid state devices.

10. A solid state inclinometer sensor system as recited in claim 8, wherein said solid state inclinometer and said magnetic field sensors provide a sourceless orientation sensor.

11. A solid state inclinometer sensor system, as recited in claim 9, wherein said sourceless orientation sensor is capable of providing compass heading angle over a 360 degree range.

12. A solid state inclinometer sensor system as recited in claim 9, wherein said processor uses data derived from said gravity sensors and from said magnetic field sensors to calculate orientation of said mounting structure and provide a digital output for transmission on said digital network.

13. A solid state inclinometer sensor system as recited in claim 12, wherein said gravity sensors include three orthogonal accelerometers and wherein said plurality of magnetic field sensors include three orthogonal magnetometers.

14. A solid state inclinometer sensor system as recited in claim 12, wherein said digital network includes a first device and a second device, wherein said first device and said second device provide data for determining an angle there between.

15. A solid state inclinometer sensor system as recited in claim 14, wherein said first device and said second device provide data for determining a dynamically changing measurement of an angle there between.

16. A solid state inclinometer sensor system as recited in claim 14, wherein said network includes multiple devices for providing posture monitoring.

17. A solid state inclinometer sensor system, as recited in claim 8, wherein said processor comprises means for scaling data from at least one from the group consisting of said inclinometer and said magnetometers with calibration coefficients.

18. A solid state inclinometer sensor system, as recited in claim 8, wherein said processor uses data derived from said magnetic field sensors to calculate compass heading.

19. A solid state inclinometer sensor system as recited in claim 8, wherein said magnetic field sensors provide outputs, further comprising amplification for said outputs.

20. A solid state inclinometer sensor system, as recited in claim 8, further wherein said processor uses information from said accelerometers to project data from said magnetic field sensors onto a horizontal earth-referenced plane.

21. A solid state inclinometer sensor system as recited in claim 1, wherein said gravity sensors are orthogonally mounted.

22. A solid state inclinometer sensor system as recited in claim 1, wherein said processor uses quadrant checking for said inclination calculation.

23. A solid state inclinometer sensor system as recited in claim 1, wherein said processor uses acceleration from said gravity sensors to determine roll over a ±

70 degree range.

24. A solid state inclinometer sensor system, as recited in claim 1, wherein said processor comprises at least one from the group consisting of a microprocessor, a digital signal processor, and a microcontroller.

25. A solid state inclinometer sensor system, as recited in claim 1, wherein said inclinometer is capable of providing pitch over a 360 degree range.

26. A solid state inclinometer sensor system, as recited in claim 25, wherein said gravity sensors include a plurality of accelerometers, wherein said inclinometer uses signs of acceleration calculated from two of said accelerometers to provide said pitch over said 360 degree range.

27. A solid state inclinometer sensor system as recited in claim 1, wherein said gravity sensors include three orthogonal accelerometers.

28. A solid state inclinometer sensor system, as recited in claim 27, wherein said processor uses acceleration from said accelerometers to determine roll over a ±

70 degree range.

29. A solid state inclinometer sensor system, as recited in claim 27, wherein said processor uses acceleration from said accelerometers to determine roll over a ±

90 degree range.

30. A solid state inclinometer sensor system, as recited in claim 1, wherein said mounting structure comprises a board, wherein said processor and said gravity sensors are all located on said board.

31. A solid state inclinometer sensor system, as recited in claim 1, wherein said mounting structure further comprises an analog signal conditioning unit, a digital signal conditioning unit, a rate responsive adaptive filter, an analog to digital converter, a temperature sensor, a digital to analog converter, and a network connector.

32. A solid state inclinometer sensor system, as recited in claim 1, wherein said mounting structure further comprises an adaptive filter.

33. A solid state inclinometer sensor system, as recited in claim 1, wherein said mounting structure further comprises an analog low pass filter to minimize effect of inertial inputs.

34. A solid state inclinometer sensor system, as recited in claim 1, wherein said mounting structure further comprises a low pass digital filter.

35. A solid state inclinometer sensor system, as recited in claim 1, wherein said mounting structure further comprises a user programmable digital filter.

36. A solid state inclinometer sensor system, as recited in claim 35, wherein said digital filter has a variable filter cutoff and wherein said filter cutoff is programmable.

37. A solid state inclinometer sensor system, as recited in claim 35, wherein said filter cutoff is set by a derivative of data from said magnetic field sensors.

38. A solid state inclinometer sensor system, as recited in claim 37, wherein said filter cutoff is set by a first derivative of said data.

39. A solid state inclinometer sensor system, as recited in claim 38, wherein said filter cutoff is programmed to increase when said first derivative of magnetometer data is small and to decrease when said first derivative of magnetic field sensor data is large.

40. A solid state inclinometer sensor system, as recited in claim 36, wherein said programmable filter can be set to provide greater filtering and lesser filtering depending on movement of the mounting structure.

41. A solid state inclinometer sensor system, as recited in claim 1, further comprising connectors for external communication.

43. A solid state inclinometer sensor system as recited in claim 1, wherein said digital network of devices are wired together on a single bus.

44. A solid state inclinometer sensor system as recited in claim 1, wherein said network includes a first device and a second device for providing measurement of an angle there between.

42. A solid state inclinometer sensor system, as recited in claim 42, wherein said connectors are connected to said digital network.

45. A solid state inclinometer sensor system as recited in claim 45, wherein said network includes said first device and said second device for providing a dynamically changing measurement of an angle there between.