SYSTEM AND METHOD FOR DETECTING THE WALK OF A PERSON

• US 20120041713A1
• Filed: 02/25/2010
• Published: 02/16/2012
• 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: Le Pulsar 5eme etage
• Inventors: Bonnet, Stéphane
• Granted Patent: US 9,265,448 B2
• Time in Patent Office: Days
• US Class Current: 702/160
• 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, furnished with a housing comprising an at least biaxial movement sensor, said housing being configured for being attached to the upper portion of the body of said person, so that a first measurement axis of said sensor is adapted to provide measurements representative of the anteroposterior axis or the vertical axis of said body and so that a second measurement axis of said sensor is adapted to provide measures representative of the mediolateral axis of said body, said system also comprising analysis means for analyzing the measurements delivered by said sensor, characterized in that said analysis means comprises:

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

detection means 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 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, in which said time window is a sliding window.

3. The system as claimed in claim 1, in which, 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, said detection means are configured for 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 Euclidian norm of the vector of measurements transmitted by said sensor and the dominant frequency of the signal of the second measurement axis.

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

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

6. The system as claimed in claim 1, wherein said analysis means are internal or external to said housing, and in which said movement sensor comprises wired or wireless transmission means for transmitting measurements to said analysis means.

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

8. The system as claimed in claim 1, wherein the sliding window is five seconds long, with a partial overlap of four seconds between two consecutive windows offset by one second.

9. The system as claimed in claim 1, wherein said means for searching for a dominant frequency for the signals transmitted by the movement sensor are configured for carrying out the search for dominant frequency by spectral analysis of the spectrogram type.

10. The system as claimed in claim 1, wherein said means for searching for a dominant frequency are configured for limiting the search for a dominant frequency along the second axis □

_ML at frequencies of between 0.25 Hz and 1 Hz.

11. The system as claimed in claim 1, wherein said means for searching for a dominant frequency are configured for limiting the search for a dominant frequency along the first axis, when the latter coincides with the anteroposterior axis, at frequencies of between the dominant frequency along the second axis □

_ML Hz increased by 0.2 Hz and 3 Hz.

12. The system as claimed in claim 1, wherein said means for searching for a dominant frequency are configured for limiting the search for a dominant frequency along the first axis, when the latter coincides with the vertical axis, at frequencies of between the dominant frequency along the second axis □

_ML Hz increased by 0.2 Hz and 3 Hz.

13. The system as claimed in claim 1, wherein said means for searching for a dominant frequency are configured for limiting the search for a dominant frequency, or for the Euclidian norm of the vector of measurements transmitted by said movement sensor, at frequencies of between the dominant frequency along the second axis □

_ML Hz increased by 0.2 Hz and 3 Hz.

14. The system as claimed in claim 1, wherein said detection means are suitable configured for 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 the walk of a person, based on measurements taken by a biaxial or triaxial movement sensor, of movements along a first measurement axis of said sensor that is configured to provide measurements representative of the anteroposterior axis (AP) or the 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 the mediolateral axis of said body, characterized in that:

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

the walk of said person is detected 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 said sensor and the dominant frequency of the signal of the second measurement axis, is substantially equal to two.