Motion tracking via body radio reflections

• US 9,753,131 B2
• Filed: 10/09/2014
• Issued: 09/05/2017
• Est. Priority Date: 10/09/2013
• Status: Active Grant

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Adib, Fadel, Kabelac, Zachary Edward, Katabi, Dina
• Primary Examiner(s): Sotomayor, John B
• Application Number:
  US14/510,263
• Publication Number:
  US 20170082741A1
• Time in Patent Office: 1,062 Days
• Field of Search: 342133, 342 22, 342 27, 342 28, 342 52, 342 56, 342 90, 342114, 342140, 342148
• CPC Class Codes: G01S 13/003 Bistatic radar systems; Multistatic radar systems
• CPC Class Codes: G01S 13/343 using sawtooth modulation
• CPC Class Codes: G01S 13/42 Simultaneous measurement of distance and other co-ordinates indirect measurement G01S13/46
• CPC Class Codes: G01S 13/584 adapted for simultaneous range and velocity measurements
• CPC Class Codes: G01S 13/72 for two-dimensional tracking, e.g. combination of angle and range tracking, track-while-scan radar
• CPC Class Codes: G01S 13/726 Multiple target tracking
• CPC Class Codes: G01S 13/878 Combination of several spaced transmitters or receivers of known location for determining the position of a transponder or a reflector G01S13/874 takes precedence
• CPC Class Codes: G01S 7/35 Details of non-pulse systems
• CPC Class Codes: G01S 7/354 Extracting wanted echo-signals Doppler systems G01S13/50
• CPC Class Codes: G01S 7/415 Identification of targets based on measurements of movement associated with the target

Abstract

A motion tracking system makes use of a number antennas to transmit and receive radio frequency signals that are reflected from objects (e.g., people) in the environment of the system, which may include one or more rooms of a building, the interior of a vehicle, etc., and may be partitioned, for example, walls or cloth sheets. In general, the objects in the environment include both fixed objects, such as chairs, walls, etc., as well as moving objects, such as but not limited to people. The system can track people, who may be moving around a room, or may be relatively stationary, for instance, sitting in a chair of lying in bed, but may nevertheless exhibit breathing motion that may be detected. The system may detect body or limb gestures made by the people in the environment, and detect physical activity including detection of falls.

Claims

1. A method for indoor localization using signal reflections from a moving body, the method comprising:

emitting a transmitted signal comprising repetitions of a transmitted signal pattern from a transmitting antenna;

receiving, at each receiving antenna of a set of receiving antennas, a received signal comprising reflections of the transmitted signal;

for each received signal,

processing the received signal to form successive patterns of reflections of the transmitting signal pattern from moving bodies, and

processing the successive patterns of reflections including retaining effects of direct reflections from said moving body and excluding at least some effects of multipath reflections from said moving body that are also reflected from at least one static object; and

determining a location of the body using a result of processing the successive patterns of reflections.

2. The method of claim 1 wherein, for each receiving antenna, excluding multipath reflections includes identifying a direct reflection from the moving body, and identifying indirect reflections from the moving body that also reflect from the at least one static object.

3. The method of claim 2 wherein, for each receiving antenna, excluding multipath reflections includes identifying a first round-trip time from the transmitting antenna to the receiving antenna, said first round-trip time representing a shortest round-trip propagation time of a signal pattern reflecting from the moving body.

4. The method of claim 3 wherein determining the location of the body includes using the identified first round-trip times for each received signal to eliminating multipath reflections corresponding to round-trip times greater than the identified first round-trip time.

5. The method of claim 4 wherein using the identified first round-trip times comprises tracking said times over successive patterns of reflections.

6. The method of claim 1 wherein the set of receiving antennas includes at least three antennas, with at least two antennas having different elevations.

7. The method of claim 6 wherein determining the location of the body comprises determining an elevation of the body.

8. The method of claim 1 further comprising detecting a pattern of motion in the tracked locations of the body.

9. The method of claim 8 wherein detecting a pattern of motion comprises detecting a temporal pattern of a trajectory of locations of the body.

10. The method of claim 8 wherein detecting a pattern of motion comprises detecting a pattern of motion in an environment of the localization.

11. The method of claim 8 wherein detecting the pattern of motion comprises detecting a gesture.

12. The method of claim 11 wherein detecting the gesture comprises detecting a whole-body gesture.

13. The method of claim 11 wherein detecting the gesture comprises detecting a limb gesture.

14. The method of claim 13 wherein detecting the gesture comprises detecting a pointing gesture.

15. The method of claim 14 wherein detecting a pointing gesture includes detecting a direction of a pointing gesture.

16. The method of claim 11 further comprising controlling an electrical or electronic device according to the detecting of the gesture.

17. The method of claim 16 wherein detecting the electrical or electronic device comprises controlling at least one of a gaming device, an appliance, and a lighting device.

18. The method of claim 8 wherein detecting the pattern of motion comprises detecting falling activity.

19. The method of claim 18 wherein detecting falling activity comprises monitoring at least one of a change in elevation, a duration of changing elevation of the body, and a proximity of a final elevation to a floor level.

20. The method of claim 1 wherein the signal pattern comprises a narrow band signal at a carrier frequency swept from a first frequency to a second frequency.

21. The method of claim 20 wherein the first frequency and the second frequency are both in a range of 5.46 to 7.25 gigahertz.

22. The method of claim 1 wherein receiving the received signal includes receiving a reflection of the transmitted signal after propagation through at least one obstruction.

23. The method claim 1 wherein the body is a person.

24. The method claim 1 wherein the body is a limb of a person.

25. A method for interaction with a device using gestures made by a person comprising:

tracking a motion of a body, including emitting a radio frequency transmitted signal comprising repetitions of a transmitted signal pattern from a transmitting antenna, receiving, at each receiving antenna of a set of receiving antennas, a received signal comprising reflections of the transmitted signal, tracking the location using successive reflections of the transmitted signal pattern;

detecting a pattern of motion using the tracked motion of the body;

using the detected pattern of motion to interact with the device.

26. The method of claim 25 wherein the tracking of the motion includes using propagation time of the transmitted signal.

27. The method of claim 26 wherein the transmitted signal pattern comprises a Frequency Modulated Carrier Wave (FMCW) signal pattern.

28. The method of claim 25 wherein the reflections of the transmitted signal comprise reflections passing through an obstruction.

29. The method of claim 25 wherein detecting the pattern of motion comprises detecting a gesture.

30. The method of claim 29 wherein detecting the gesture includes detecting a two-dimensional gesture.

31. The method of claim 29 wherein detecting the gesture includes detecting a three-dimensional gesture.

32. The method of claim 29 wherein detecting the gesture comprises detecting a whole-body gesture.

33. The method of claim 29 wherein detecting the gesture comprises detecting a limb gesture.

34. The method of claim 33 wherein detecting the limb gesture includes distinguishing a reflection from a limb from a reflection of a whole body of a person according to a size of the reflection.

35. The method of claim 33 wherein detecting the gesture comprises detecting a pointing gesture.

36. The method of claim 29 further comprising controlling an electrical or electronic device according to the detecting of the gesture.

37. A method for detecting fall of a person comprising:

tracking a motion of the person, including emitting a radio frequency transmitted signal comprising repetitions of a transmitted signal pattern from a transmitting antenna, receiving, at each receiving antenna of a set of receiving antennas, a received signal comprising reflections of the transmitted signal, tracking the location using successive reflections of the transmitted signal pattern;

detecting a pattern of motion using the tracked motion of the body;

using the detected pattern of motion to detect a fall of the person.

38. The method of claim 37 wherein the reflections of the transmitted signal comprise reflections passing through an obstruction.

39. The method of claim 37 wherein detecting the pattern of motion comprises monitoring at least one of a change in elevation, a duration of changing elevation of the body, and a proximity of a final elevation to a floor level.

40. The method of claim 39 wherein detecting the pattern of motion comprises monitoring a change of elevation includes detecting a change of elevation of at least a threshold value.

41. The method of claim 39 wherein detecting the pattern of motion comprises monitoring the duration of changing elevation includes detecting a duration less than a threshold value.

42. The method of claim 39 wherein detecting the pattern of motion comprises monitoring proximity of the final elevation includes detecting a final elevation less than a threshold value.

43. The method of claim 39 wherein detecting the pattern of motion comprises detecting when each condition of the group of conditions consisting of a change of elevation of at least a first threshold value, a duration less than a second threshold value, and a final elevation less than a third threshold value, are satisfied.

44. A system comprising:

a transmitting antenna and a set of receiving antenna;

a transmitter coupled to the transmitting antenna and configured to generate a transmitting signal comprising repetitions of a transmitting signal pattern;

a receiver coupled to the set of receiving antennas, for receiving signals comprising reflections of the transmitting signal;

a processor coupled to the transmitter and to the receiver, configured to cause the system to

emit a transmitted signal comprising repetitions of a transmitted signal pattern from a transmitting antenna;

receive, at each receiving antenna of a set of receiving antennas, a received signal comprising reflections of the transmitted signal;

for each received signal,

process the received signal to form successive patterns of reflections of the transmitting signal pattern from moving bodies, and

process the successive patterns of reflections including retaining effects of direct reflections from said moving body and excluding at least some effects of multipath reflections from said moving body that are also reflected from at least one static object; and

determine a location of the body using a result of processing the successive patterns of reflections.