Method and apparatus for determining orientation

• US 6,816,437 B1
• Filed: 07/17/2002
• Issued: 11/09/2004
• Est. Priority Date: 06/03/2002
• Status: Expired due to Fees

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Miu, Allen K. L., Priyantha, Nissanka B., Balakrishnan, Hari, Teller, Seth J.
• Primary Examiner(s): Lobo, Ian J.
• Application Number:
  US10/198,625
• Time in Patent Office: 846 Days
• Field of Search: 367/124, 367/125, 367/129, 702/150, 340/870.41
• US Class Current: 367/125
• CPC Class Codes: G01S 5/186 Determination of attitude using inertial means G01C9/00; control of attitude G05D1/49

Abstract

The position and orientation of a mobile unit is determined from ultrasonic waves received from beacons of known location. Orientation is determined from a phase difference of the sensed ultrasonic wave at plural receivers on the mobile unit. Signals from multiple beacons may be processed to solve for x, y and z position and for speed of sound. The receivers are spaced at greater than a half wavelength of the ultrasonic wave and signals from plural receivers are processed to remove multiple wavelength phase ambiguity. Two non-collinear sets of collinear receivers allow ambiguity resulting from symmetry of the receivers to be broken.

Claims

1. A system for determining orientation of first and second units relative to each other comprising:

a beacon on the first unit, transmitting a wave;

plural receivers, each fixed relative to the second unit, the plural receivers sensing the transmitted wave to provide plural sensed signals of periodic waveforms; and

a processor that processes the sensed signals to specify orientation in a 360°

range of the second unit relative to the beacon based on phase differences between the periodic waveforms of the plural sensed signals that provide a differential distance measurement.

2. A system as claimed in claim 1 wherein the wave is an ultrasonic wave.

3. A system as claimed in claim 1 wherein the specified orientation includes angular orientation within a plane offset from the beacon.

4. A system as claimed in claim 3 wherein the plane is offset from a plane of plural beacons.

5. A system as claimed in claim 3 wherein the sensed signals are processed to specify orientation based on phase differences of sensed signals from plural beacons and on position relative to each of the plural beacons.

6. A system as claimed in claim 5 wherein the position is determined from measured distances relative to each of plural beacons.

7. A system as claimed in claim 5 comprising at least four beacons, the sensed signals being processed to solve for x, y and z position and for speed of sound.

8. A system as claimed in claim 7 wherein receivers are spaced at a length greater than a half wavelength of the transmitted wave, the system comprising at least three receivers, the sensed signals being processed to remove phase ambiguity of multiple phases separated by 2π

.

9. A system as claimed in claim 8 wherein the wave is an ultrasonic wave.

10. A system as claimed in claim 1 wherein receivers are spaced at a length greater than the half wavelength of the transmitted wave, the system comprising at least three receivers, the sensed signals being processed to remove phase ambiguity of multiple phases separated by 2π

.

11. A system as claimed in claim 10 wherein the at least three receivers are in a line spaced by distances that are relatively prime integral multiples of the half wavelength of the transmitted wave.

12. A system as claimed in claim 10 comprising two non-collinear sets of collinear receivers to break symmetry of the receivers.

13. A system as claimed in claim 12 wherein each set of receivers comprises three collinear receivers, the sets of receivers being perpendicular to each other and sharing one receiver.

36. A system as claimed in claim 8 wherein phase ambiguity is removed independent of signal modulation.

37. A system as claimed in claim 10 wherein phase ambiguity is removed independent of signal modulation.

40. A system as claimed in claim 8 wherein the sensed pairs of signals received at each of respective pairs of receivers result in multiple potential solutions due to phase ambiguity that are resolved based on concurrence of solutions for multiple pairs.

41. A system as claimed in claim 10 wherein the sensed pairs of signals received at each of respective pairs of receivers result in multiple potential solutions due to phase ambiguity that are resolved based on concurrence of solutions for multiple pairs.

14. A method of determining orientation of first and second units relative to each other comprising:

from a beacon on the first unit, transmitting a wave;

at each of plural receivers fixed relative to the second unit, sensing the transmitted wave to provide plural sensed signals of periodic waveforms; and

processing the sensed signals to specify orientation in a 360°

range of the plural receivers and of the second unit relative to the beacon based on phase differences between the periodic waveforms of the plural sensed signals that proved a differential distance measurement.

15. A system as claimed in claim 14 wherein the wave is an ultrasonic wave.

16. A method as claimed in claim 14 wherein the specified orientation includes angular orientation within a plane offset from the beacon.

17. A method as claimed in claim 16 wherein the plane is offset from a plane of plural beacons.

18. A method as claimed in claim 16 wherein the sensed signals are processed to specify orientation based on phase differences of sensed signals from plural beacons and on position relative to each of the plural beacons.

19. A method as claimed in claim 18 wherein the position is determined from measured distances relative to each of plural beacons.

20. A method as claimed in claim 18 wherein the sensed signals are from at least four beacons and are processed to solve for x, y and z position and for speed of sound.

21. A method as claimed in claim 20 wherein receivers are spaced at a length greater than a half wavelength of the transmitted wave, and the sensed signals are sensed by at least three receivers and are processed to remove phase ambiguity of multiple phases separated by 2π

.

22. A method as claimed in claim 21 wherein the wave is an ultrasonic wave.

23. A method as claimed in claim 14 wherein receivers are spaced at a length greater than a half wavelength of the transmitted wave, and the sensed signals are sensed by at least three receivers and are processed to remove phase ambiguity of multiple phases separated by 2π

.

24. A method as claimed in claim 23 wherein the last at least three receiver are in a line spaced by distances that are relatively prime integral multiples of the half wavelength of the transmitted wave.

25. A method as claimed in claim 23 wherein the sensed signals are from two non-collinear sets of collinear receivers to break symmetry of the receivers.

26. A method as claimed in claim 25 wherein each set of receivers comprise three collinear receivers, the sets of receivers being perpendicular to each other and sharing one receiver.

38. A method as claimed in claim 21 wherein phase ambiguity is removed independent of signal modulation.

39. A method as claimed in claim 23 wherein phase ambiguity is removed independent of signal modulation.

42. A system as claimed in claim 21 wherein the sensed pairs of signals received at each of respective pairs of receivers result in multiple potential solutions due to phase ambiguity that are resolved based on concurrence of solutions for multiple pairs.

43. A system as claimed in claim 23 wherein the sensed pairs of signals received at each of respective pairs of receivers result in multiple potential solutions due to phase ambiguity that are resolved based on concurrence of solutions for multiple pairs.

27. A system for determining orientation of first and second units relative to each other comprising:

a beacon on the first unit, transmitting a wave;

plural receivers, each fixed relative to the second unit, the plural receivers sensing the transmitted wave to provide plural sensed signals of periodic waveforms; and

means for processing the sensed signals to specify orientation in a 360°

range of the plural receivers and of the second unit relative to the beacon based on phase differences between the periodic waveforms of the plural sensed signals that provide a differential distance measurement.

28. A system for determining orientation of first and second units relative to each other comprising:

a beacon on the first unit, transmitting a wave;

at least three receivers, each fixed relative to the second unit, the receiver being spaced at a length greater than a half wavelength of the transmitted wave and sensing the transmitted wave to provide plural sensed signals of periodic waveforms; and

a processor that processes the sensed signals to specify orientation of the second unit relative to the beacon based on phase differences between the periodic waveforms of the plural sensed signals, the sensed signals being processed to remove phase ambiguity of multiple phases separated by 2π

independent of signal modulation.

29. A system as claimed in claim 28 wherein the at least three receivers are in a line spaced by distances that are relatively prime integral multiples of the half wavelength of the transmitted wave.

30. A system as claimed in claim 29 comprising two non-collinear sets of collinear receivers to break symmetry of the receivers.

31. A system as claimed in claim 30 wherein each set of receivers comprises three collinear receivers, the sets of receivers being perpendicular to each other and sharing one receiver.

32. A method of determining orientation of first and second units relative to each other comprising:

from a beacon on the first unit, transmitting a wave;

at each of at least three receivers fixed relative to the second unit and spaced at a length greater than a half wavelength of the transmitted wave, sensing the transmitted wave to provide plural sensed signals of periodic waveforms; and

processing the sensed signals to specify orientation of the plural receivers and of the second unit relative to the beacon based on phase differences between the periodic waveforms of the plural sensed signals, the sensed signals being processed to remove phase ambiguity of multiple phases separated by 2π

independent of signal modulation.

33. A method as claimed in claim 32 wherein the at least three receivers are in a line spaced by distances that are relatively prime integral multiples of the half wavelength of the transmitted wave.

34. A method as claimed in claim 33 wherein the sensed signals are from two non-collinear sets of collinear receivers to break symmetry of the receivers.

35. A method as claimed in claim 34 wherein each set of receivers comprises three collinear receivers, the sets of receivers being perpendicular to each other and sharing one receiver.

44. A system for determining orientation of first and second units relative to each other comprising:

a beacon on the first unit, transmitting a wave;

at least three receivers, each fixed relative to the second unit, the receivers being spaced at a length greater than a half wavelength of the transmitted wave and sensing the transmitted wave to provide plural sensed signals of periodic waveforms; and

a processor that processes the sensed signals to specify orientation of the second unit relative to the beacon based on phase differences between the periodic waveforms of the plural sensed signals, the sensed signals being processed to remove phase ambiguity of multiple phases separated by 2π

, the sensed pair of signals received at each of respective pairs of receivers resulting in multiple potential solutions due to phase ambiguity that are resolved based on a concurrence of solutions from multiple pairs.

45. A system as claimed in claim 44 wherein the at least three receivers are in a line spaced by distances that are relatively prime integral multiples of the half wavelength of the transmitted wave.

46. A system as claimed in claim 44 comprising two non-collinear sets of collinear receivers to break symmetry of the receivers.

47. A system as claimed in claim 44 wherein each set of receivers comprises three collinear receivers, the sets of receivers being perpendicular to each other and sharing one receiver.

48. A method of determining orientation of first and second units relative to each other comprising:

a beacon on the first unit, transmitting a wave;

at each of at least three receivers fixed relative to the second unit and spaced at a length greater than a half wavelength of the transmitted wave, sensing the transmitted wave to provide plural sensed signals of periodic waveforms; and

processing the sensed signals to specify orientation of the plural receivers and of the second unit relative to the beacon based on phase differences between the periodic waveforms of the plural sensed signals, the sensed signals being processed to remove phase ambiguity of multiple phases separated by 2π

, the sensed pair of signals received at each of respective pairs of receivers resulting in multiple potential solutions due to phase ambiguity that are resolved based on a concurrence of solutions from multiple pairs.

49. A method as claimed in claim 48 wherein the at least three receivers are in a line spaced by distances that are relatively prime integral multiples of the half wavelength of the transmitted wave.

50. A method as claimed in claim 48 wherein the sensed signals are from two non-collinear sets of collinear receivers to break symmetry of the receivers.

51. A method as claimed in claim 48 wherein each set of receivers comprises three collinear receivers, the sets of receivers being perpendicular to each other and sharing one receiver.