System and method for detecting the walk of a person

• US 9,265,448 B2
• Filed: 02/25/2010
• Issued: 02/23/2016
• Est. Priority Date: 02/26/2009
• Status: Active Grant

• Current Assignee: Commissariat a L'Energie Atomique (French Alternative Energies and Atomic Energy Commission), Movea SA (TDK Corporation)
• Original Assignee: Commissariat a L'Energie Atomique (French Alternative Energies and Atomic Energy Commission), Movea
• Inventors: Bonnet, Stphane
• Primary Examiner(s): DO, AN H
• Application Number:
  US13/203,461
• Publication Number:
  US 20120041713A1
• Time in Patent Office: 2,189 Days
• Field of Search: 702/160, 702/155, 702/158
• US Class Current: 1/1
• CPC Class Codes: A61B 5/1038 Measuring plantar pressure during gait
• CPC Class Codes: A61B 5/1118 Determining activity level
• CPC Class Codes: A61B 5/1123 Discriminating type of movement, e.g. walking or running A61B5/1116, A61B5/112 take precedence
• CPC Class Codes: G01C 21/1654 with electromagnetic compass
• CPC Class Codes: G01C 22/006 Pedometers
• CPC Class Codes: G06F 17/16 Matrix or vector computation , e.g. matrix-matrix or matrix-vector multiplication, matrix factorization matrix transposition G06F7/78

Abstract

A system for detecting the walk of a person has a housing (BT) with at least a biaxial movement sensor (CM). The housing is attached to the upper portion of the body of the person, so that a first measurement axis of the sensor (CM) coincides with the anteroposterior axis (AP) or the vertical axis (VT) of the body and so a second measurement axis of said sensor (CM) coincides with the mediolateral axis (ML) of the body. An analysis means (MA) analyzes the measurements delivered by the sensor (CM). The analysis means includes a processing means (MT) for processing over a time window the measurement signals delivered by the sensor (CM), which includes means for searching for a dominant frequency (MRFD) in said signals. The analysis means also includes a detection means (MD) for detecting the walk of the person when a ratio between the dominant frequency of the signal of the first measurement axis and the dominant frequency of the second measurement axis, or between the dominant frequency of a Euclidian norm of the vector of measurements transmitted by the sensor (CM) and the dominant frequency of the signal of the second measurement axis, is substantially equal to two.

Claims

1. A system for detecting the walk of a person, the system including a housing comprising at least a biaxial movement sensor, said housing configured to attach to an upper portion of the body of said person, so that a first measurement axis of said sensor provides measurements representative of an anteroposterior axis or a vertical axis of said body and so that a second measurement axis of said sensor provides measurements representative of a mediolateral axis of said body, said system further comprising a processor configured to analyze the measurements delivered by said sensor by performing steps comprising:

processing over a time window the measurement signals delivered by said sensor to search for a dominant frequency in said signals, and

detecting walking of the person as occurring when a ratio between the dominant frequency of the signal of the first measurement axis and the dominant frequency of the second measurement axis, or between the dominant frequency of a norm of the vector of measurements transmitted by said sensor and the dominant frequency of the signal of the second measurement axis, is substantially equal to two.

2. The system as claimed in claim 1, wherein said time window is a sliding window.

3. The system as claimed in claim 2, wherein the sliding window is five seconds long, with a partial overlap of four seconds between two consecutive windows offset by one second.

4. The system as claimed in claim 1, wherein said movement sensor is triaxial, the first measurement axis of said sensor coincides with the anteroposterior axis of said body, the second measurement axis of said sensor coincides with the mediolateral axis of said body, and the third measurement axis of said sensor coincides with the vertical axis of said body, and detecting the walk of the person further comprises detecting a ratio substantially equal to two between the dominant frequency of the signal of the first measurement axis and the dominant frequency of the second measurement axis, or between the dominant frequency of the signal of the third measurement axis and the dominant frequency of the second measurement axis, or between the dominant frequency of a norm of the vector of measurements transmitted by said sensor and the dominant frequency of the signal of the second measurement axis.

5. The system as claimed in claim 1, further comprising high-pass filters.

6. The system as claimed in claim 1, further comprising band-pass filters.

7. The system as claimed in claim 1, wherein said processor is internal or external to said housing, and wherein said movement sensor comprises wired or wireless transmitter for transmitting measurements to said processor.

8. The system as claimed in claim 1, wherein said movement sensor is a biaxial or triaxial accelerometer, or a biaxial or triaxial magnetometer or a biaxial or triaxial gyrometer.

9. The system as claimed in claim 1, wherein searching for the dominant frequency for the signals transmitted by the movement sensor comprises carrying out the search for the dominant frequency by a spectral analysis.

10. The system as claimed in claim 1, wherein searching for the dominant frequency is limited to a dominant frequency along the second axis f_ML at frequencies of between 0.25 Hz and 1 Hz.

11. The system as claimed in claim 1, wherein searching for the dominant frequency is limited to a dominant frequency along the first axis, when the latter coincides with the anteroposterior axis, at frequencies between the dominant frequency along the second axis f_ML increased by 0.2 Hz to 3 Hz.

12. The system as claimed in claim 1, wherein searching for the dominant frequency is limited to a dominant frequency along the first axis, when the latter coincides with the vertical axis, at frequencies between the dominant frequency along the second axis f_ML increased by 0.2 Hz to 3 Hz.

13. The system as claimed in claim 1, wherein searching for the dominant frequency is limited to a dominant frequency, or for a norm of a vector of measurements transmitted by said movement sensor, at frequencies between the dominant frequency along the second axis f_ML increased by 0.2 Hz to 3 Hz.

14. The system as claimed in claim 1, wherein detecting the walk of the person comprises detecting a ratio of said frequencies substantially equal to two, to within a variance, when the powers of the respective signals are also higher than a threshold.

15. The system as claimed in claim 1, wherein said housing is configured for attachment to the torso or to the sacrum of said person.

16. A method for detecting a walk of a person, the method comprising:

obtaining measurements from a biaxial or triaxial movement sensor, of movements along a first measurement axis of said sensor that is configured to provide measurements representative of an anteroposterior axis (AP) or a vertical axis of the body of said person and along a second measurement axis of said sensor that is configured to provide measurements representative of a mediolateral axis of said body,

processing, over a time window, the measurement signals delivered by said movement sensor, said processing comprising a search for a dominant frequency in said signals, and

detecting walking of said person as occurring when a ratio between the dominant frequency of the signal of the first measurement axis and the dominant frequency of the second measurement axis, or between the dominant frequency of a norm of the vector of measurements transmitted by said sensor and the dominant frequency of the signal of the second measurement axis, is substantially equal to two.