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EP2400889A1 - System and method for detecting the walk of a person - Google Patents

System and method for detecting the walk of a person

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Publication number
EP2400889A1
EP2400889A1 EP10705367A EP10705367A EP2400889A1 EP 2400889 A1 EP2400889 A1 EP 2400889A1 EP 10705367 A EP10705367 A EP 10705367A EP 10705367 A EP10705367 A EP 10705367A EP 2400889 A1 EP2400889 A1 EP 2400889A1
Authority
EP
European Patent Office
Prior art keywords
axis
dominant frequency
sensor
measurement
person
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
EP10705367A
Other languages
German (de)
French (fr)
Inventor
Stéphane BONNET
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Movea SA
Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Original Assignee
Commissariat a lEnergie Atomique CEA
Movea SA
Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Commissariat a lEnergie Atomique CEA, Movea SA, Commissariat a lEnergie Atomique et aux Energies Alternatives CEA filed Critical Commissariat a lEnergie Atomique CEA
Publication of EP2400889A1 publication Critical patent/EP2400889A1/en
Ceased legal-status Critical Current

Links

Classifications

    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/103—Measuring devices for testing the shape, pattern, colour, size or movement of the body or parts thereof, for diagnostic purposes
    • A61B5/11—Measuring movement of the entire body or parts thereof, e.g. head or hand tremor or mobility of a limb
    • A61B5/112—Gait analysis
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/103—Measuring devices for testing the shape, pattern, colour, size or movement of the body or parts thereof, for diagnostic purposes
    • A61B5/1036—Measuring load distribution, e.g. podologic studies
    • A61B5/1038—Measuring plantar pressure during gait
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/103—Measuring devices for testing the shape, pattern, colour, size or movement of the body or parts thereof, for diagnostic purposes
    • A61B5/11—Measuring movement of the entire body or parts thereof, e.g. head or hand tremor or mobility of a limb
    • A61B5/1113—Local tracking of patients, e.g. in a hospital or private home
    • A61B5/1114—Tracking parts of the body
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/103—Measuring devices for testing the shape, pattern, colour, size or movement of the body or parts thereof, for diagnostic purposes
    • A61B5/11—Measuring movement of the entire body or parts thereof, e.g. head or hand tremor or mobility of a limb
    • A61B5/1116—Determining posture transitions
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/103—Measuring devices for testing the shape, pattern, colour, size or movement of the body or parts thereof, for diagnostic purposes
    • A61B5/11—Measuring movement of the entire body or parts thereof, e.g. head or hand tremor or mobility of a limb
    • A61B5/1118—Determining activity level
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/103—Measuring devices for testing the shape, pattern, colour, size or movement of the body or parts thereof, for diagnostic purposes
    • A61B5/11—Measuring movement of the entire body or parts thereof, e.g. head or hand tremor or mobility of a limb
    • A61B5/1123—Discriminating type of movement, e.g. walking or running
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/68—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient
    • A61B5/6801—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient specially adapted to be attached to or worn on the body surface
    • A61B5/683—Means for maintaining contact with the body
    • A61B5/6831—Straps, bands or harnesses
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/72—Signal processing specially adapted for physiological signals or for diagnostic purposes
    • A61B5/7225—Details of analogue processing, e.g. isolation amplifier, gain or sensitivity adjustment, filtering, baseline or drift compensation
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/72—Signal processing specially adapted for physiological signals or for diagnostic purposes
    • A61B5/7235—Details of waveform analysis
    • A61B5/725—Details of waveform analysis using specific filters therefor, e.g. Kalman or adaptive filters
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
    • G01C21/00—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00
    • G01C21/10—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00 by using measurements of speed or acceleration
    • G01C21/12—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00 by using measurements of speed or acceleration executed aboard the object being navigated; Dead reckoning
    • G01C21/16—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00 by using measurements of speed or acceleration executed aboard the object being navigated; Dead reckoning by integrating acceleration or speed, i.e. inertial navigation
    • G01C21/165—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00 by using measurements of speed or acceleration executed aboard the object being navigated; Dead reckoning by integrating acceleration or speed, i.e. inertial navigation combined with non-inertial navigation instruments
    • G01C21/1654—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00 by using measurements of speed or acceleration executed aboard the object being navigated; Dead reckoning by integrating acceleration or speed, i.e. inertial navigation combined with non-inertial navigation instruments with electromagnetic compass
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
    • G01C22/00—Measuring distance traversed on the ground by vehicles, persons, animals or other moving solid bodies, e.g. using odometers, using pedometers
    • G01C22/006—Pedometers
    • G—PHYSICS
    • G06—COMPUTING OR CALCULATING; COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F17/00—Digital computing or data processing equipment or methods, specially adapted for specific functions
    • G06F17/10—Complex mathematical operations
    • G06F17/16—Matrix or vector computation, e.g. matrix-matrix or matrix-vector multiplication, matrix factorization
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B2562/00—Details of sensors; Constructional details of sensor housings or probes; Accessories for sensors
    • A61B2562/02—Details of sensors specially adapted for in-vivo measurements
    • A61B2562/0219—Inertial sensors, e.g. accelerometers, gyroscopes, tilt switches

Definitions

  • the invention relates to a system and method for detecting the walking of a person, or in other words the detection of a displacement of a person by a mode of locomotion constituted by a sequence of steps.
  • the detection of a person's walking activity is information that makes it possible, for example, to estimate a person's energy expenditure, to evaluate a person's sedentary level, or to estimate the quality of a person's energy expenditure. or loss of functional ability after surgery or drug therapy.
  • SUBSTITUTE SHEET (RULE 26) allows to study the stability of walking. It is not a question here of detecting a walking activity, but of analyzing or characterizing a walking activity of a person who is already known to be walking.
  • a gait detection system of a person provided with a housing comprising a biaxial or triaxial motion sensor.
  • the housing is adapted to be fixed on the upper part of the body of said person, so that a first measurement axis of said sensor coincides with the anteroposterior axis or the vertical axis of said body and a second axis of measurement of said sensor coincides with the medio-lateral axis of said body, said system being, furthermore, provided with means for analyzing the measurements delivered by said sensor.
  • Said analysis means comprise:
  • the time window is a slippery window.
  • said motion sensor being 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 adapted to detect 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 axis of measuring, 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 Euclidean norm of the measurement vector transmitted by said sensor and the dominant frequency of the signal of the second measuring axis.
  • the system further comprises high-pass filters.
  • the system further comprises band-pass filters, for example of frequency band between 0.5 and 10 Hz.
  • band-pass filters for example of frequency band between 0.5 and 10 Hz.
  • said analysis means are internal or external to said housing, and said motion sensor comprises wired or wireless transmission means for transmitting its measurements to said analysis means.
  • the analysis means can be integrated in the housing or located on a remote basis, and the output signals of the housing, analyzed or not, can be transmitted with or without wire.
  • Said motion sensor may be a biaxial or triaxial accelerometer, a biaxial or triaxial magnetometer, or a biaxial or triaxial gyro.
  • the invention works with all these types of motion sensors.
  • the sliding time window has a duration of five seconds, with a partial overlap of four seconds between two consecutive windows shifted by one second.
  • said search means of a dominant frequency for the signals transmitted by the motion sensor are adapted to perform the dominant frequency search, in each time window, by spectral analysis.
  • this spectral analysis may be of the spectrogram type.
  • the spectrogram which uses the square of the Fourier transform module of the convolved signal to an apodization window, is a simple, reliable, and low-cost way of searching for a dominant frequency, ie the frequency corresponding to the maximum signal power.
  • Said search means of a dominant frequency can be adapted to limit the search for a VML dominant frequency according to the second axis at frequencies between 0.25 Hz and 1 Hz.
  • Said search means of a dominant frequency can be adapted to limit the search for a dominant frequency along the first axis, when it coincides with the antero-hitch-hopping axis, at frequencies within a predetermined range of frequencies. This frequency range can be limited by the dominant frequency along the second axis f M ⁇ _ Hz increased by 0.2 Hz and 3 Hz ([f ML +0.2; 3]).
  • this range may be bounded by the dominant frequency along the second axis f M ⁇ _ Hz increased by 0.25 Hz and 2 Hz, ([f ML +0.25; 2]).
  • Said search means of a dominant frequency can be adapted to limit the search for a dominant frequency along the first axis, when it coincides with the vertical axis, at frequencies within a predetermined range of frequencies.
  • This frequency range can be limited by the dominant frequency along the second axis f M ⁇ _ Hz increased by 0.2 Hz and 3 Hz ([f M ⁇ _ + 0.2; 3]).
  • Said search means of a dominant frequency can be adapted to limit the search for a dominant frequency for the Euclidean standard of the measurement vector transmitted by said motion sensor, at frequencies within a predetermined range of frequencies. This frequency range can be limited by the dominant frequency along the second axis f M ⁇ _ Hz increased by 0.2 Hz and 3 Hz ([f ML +0.2; 3]).
  • said detection means are adapted to detect a ratio of said dominant frequencies substantially equal to two, to a precision, when, moreover, at least on one axis, the power of the signal, at least one frequency , is greater than a threshold.
  • Such a ratio is determined or exploited only for windows having, on at least one axis, at least one frequency whose power is greater than a determined threshold, this threshold possibly being called a power threshold.
  • This power threshold is determined a priori, or adjusted experimentally, for example during a test phase.
  • This power condition of at least one frequency can be applied to at least one axis, but also to all axes. Note that when this power condition is applied on different axes, each power threshold may be different from each other.
  • said determination means are adapted to determine the ratio of the dominant frequencies, corresponding to a given time window, when, on at least one axis, the dominant frequency has a power greater than a threshold power.
  • This threshold condition can be applied only to the dominant frequency, but also to other defined frequencies or frequency bands.
  • this threshold power criterion can also be applied to the Euclidean norm of the vector of measurements. For each time window, then check the frequency or frequencies, for example the dominant frequency, have a power greater than a power threshold.
  • This power threshold can be fixed a priori or by previously determining a power in a time interval during which nothing happens, for example during anatomical calibration.
  • said housing is adapted to be fixed on the torso or on the sacrum of said person.
  • the amplitude of the oscillations of the trunk is higher, which improves the accuracy of the system.
  • the fixation at the level of the sacrum is particularly easy and discreet, for example by means of a belt.
  • a method for detecting a person's walking from measurements made by a biaxial or triaxial motion sensor, of movements along a first measurement axis of said sensor coinciding with the anteroposterior axis or the vertical axis of the body of said person and along a second axis measuring said sensor coinciding with the medio-lateral axis of said body, in which:
  • the measurement signals delivered by said motion sensor are processed over a time window, said processing comprising a search for a dominant frequency in said signals and
  • the step 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 Euclidean 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.
  • the processing is performed on a sliding time window.
  • FIG. 1 schematically illustrates an embodiment of a system, according to one aspect of the invention
  • FIG. 3 illustrates an example of measurements made by a system according to FIG. 1, in which the motion sensor is a biaxial accelerometer;
  • FIGS. 4 and 5 illustrate the operation of the analysis means
  • FIGS. 6a and 6b illustrate a first mode of implementation of the system according to one aspect of the invention
  • FIGS. 7a, 7b and 7c illustrate a second mode of implementation of the system according to one aspect of the invention
  • FIGS. 8a and 8b illustrate a third mode of implementation of the system according to one aspect of the invention.
  • FIGS. 9a and 9b illustrate a fourth mode of implementation of the system according to one aspect of the invention.
  • FIGS. 10a and 10b illustrate a fifth mode of implementation of the system according to one aspect of the invention.
  • the elements having the same references are similar.
  • a person's walking detection system comprises a BT housing comprising a biaxial or triaxial CM motion sensor.
  • the housing BT is adapted to be fixed on the upper part of the body of said person, in this case by means of a resilient fastening belt CEF, so that a first measurement axis of said motion sensor coincides with the anterior-posterior axis AP or the vertical axis VT of said body and a second measurement axis of said motion sensor coincides with the medio-lateral axis ML of said body.
  • any other means of attachment may be suitable.
  • This coincidence can, for example, be made by anatomical calibration, for example by asking the person to whom the BT housing was fixed to stand as straight as possible for a few seconds against a wall, the system, in a known manner , determines the rotation matrix to be applied to the measurements to deliver measurements brought back to the medio-lateral axes ML, anteroposterior AP or vertical VT.
  • the motion sensor CM is also provided with a transmission module MTR for transmitting the measurements, in this example by wireless transmission, to an external station SE, in this case a laptop.
  • the motion sensor may, for example, be a biaxial or triaxial accelerometer, a biaxial or triaxial magnetometer, or a biaxial or triaxial gyro.
  • the motion sensor CM will be a biaxial accelerometer whose first measurement axis coincides with the anteroposterior axis AP of the body of the person, and the second axis of measurement coincides with the medial-lateral axis ML of the body of the person.
  • the second measurement axis of the accelerometer may coincide with the medial-lateral axis ML of the body of the person, and the first measurement axis may coincide with the vertical axis VT of the body of the person.
  • the portable computer SE comprises an analysis module MA of the data transmitted by the accelerometer CM.
  • the analysis module can be integrated into the LV box.
  • the analysis module is adapted to sample the signals received from the accelerometer CM at a sampling frequency less than or equal to 1 kHz, and typically of the order of 10 to 200 Hz.
  • the analysis module MA comprises a processing module MT for processing the measurement signals delivered by the accelerometer CM.
  • the detection module is adapted to detect 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 third axis signal. measurement and the dominant frequency of the second measurement axis, or between the dominant frequency of a Euclidean norm of the measurement vector transmitted by said sensor and the dominant frequency of the signal of the second measurement axis. We then have an improved detection precision.
  • a ratio or ratio substantially equal to 2 a ratio for example between 1.7 and 2.3, and preferably between 1.9 and 2.1.
  • This ratio can be predetermined, but also adjusted experimentally, especially during a test phase. We then analyze precisely the different values taken by this ratio when the person walks, and we determine the critical value that will be implemented in the algorithm. This determination can be made statistically, considering the risks associated with false positives (the device indicates that the person is walking when it is not working) or false negatives (the device indicates that the person does not 'she walks).
  • the processing module MT may comprise high-pass filters, FPH for deleting the respective continuous components of the signals transmitted by the accelerometer CM, to be able to accurately detect the dominant frequency.
  • the processing module MT may also include bandpass filters so as to greatly limit the influence of noises or frequencies of signals unrelated to walking.
  • the processing module MT comprises a search module of a dominant frequency MRFD for the signals transmitted by the motion sensor, by spectral analysis.
  • Spectral analysis which consists in estimating the signal power as a function of frequency, is a known, simple and inexpensive way of calculating to search for a dominant frequency in a signal.
  • dominant frequency is meant the frequency which corresponds to the maximum of the power density of the signal.
  • the spectral analysis can be carried out using a Fourier transform, but also other techniques known to those skilled in the art, for example a wavelet transform, a technique better adapted to nonstationary signals.
  • the analysis module MA also comprises a detection module MD of the step 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 the a Euclidean 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.
  • the present invention operates without the need for a physical calibration of the motion sensor CM, or, in other words, a system according to the invention operates from the raw data expressed in numerical unit or in volts and the knowledge of the gains and offsets of the CM motion sensor is not essential. If we decide not to transform the volts into a physical unit (for example m / s 2 for an accelerometer) the notion of minimum power threshold can be decided from a measurement of the person in a state of rest and not more from a kinematic data.
  • the medio-lateral axis ML of the body is oriented from the left part of the body to the right part of the body
  • the anteroposterior axis AP is oriented from the rear part of the body towards the front part of the body
  • the vertical axis is oriented from the upper body to the lower part of the body.
  • the housing can be disposed at the torso, or at the level of the sacrum.
  • the band-pass filter FPB may, for example be a Butterworth filter of order 4 filtering in the frequency band between 0.5 and 10 Hz, particularly well suited to walking.
  • the signals are divided into analysis time windows, the time windows being preferably sliding time windows, for example in five-second windows, with a partial overlap of four seconds between two consecutive windows shifted by one second. For each time window, it then seeks dominant frequencies of signals.
  • the search module of a MRFD dominant frequency by spectral analysis of spectrogram type can be adapted to limit the search for a dominant frequency along the first axis f M ⁇ _ at frequencies between 0.25 Hz and 1 Hz.
  • the search module for a dominant frequency MRFD by spectral analysis can also be adapted to limit the search for a dominant frequency along the first axis, when it coincides with the anteroposterior axis AP, at frequencies between the dominant frequency along the second axis f M ⁇ _ Hz increased by 0.2 Hz and 3 Hz, or at frequencies between the dominant frequency along the second axis f M ⁇ _ Hz increased by 0.25 Hz and 2 Hz ([f M ⁇ _ + 0.25 ;
  • the search module of a dominant frequency MRFD by spectral analysis can also be adapted to limit the search for a dominant frequency along the first axis, when it coincides with the vertical axis VT, at frequencies between the frequency dominant according to the second axis f M ⁇ _ Hz increased by 0.2 Hz and 3 Hz.
  • the module for finding a MRFD dominant frequency by spectral analysis may also be adapted to limit the search for a dominant frequency for the Euclidean norm of the vector of measurements transmitted by said CM motion sensor, at frequencies between the dominant frequency along the second axis f M ⁇ _ Hz increased by 0.2 Hz and 3 Hz.
  • FIG. 3 represents an example of signals S M 1 and S A p transmitted by a housing BT according to one aspect of the invention, provided with a biaxial accelerometer CM, whose first measurement axis coincides with the anteroposterior axis. AP, and the second measurement axis coincides with the medio-lateral axis ML, as a function of time.
  • the BT housing is, for example, disposed at the sacrum of the person, whose activity is monitored.
  • FIG. 4 represents, for the case of the data of FIG. 3, the dominant frequencies f M ⁇ _ and f A p as a function of time, corresponding to the signals S M ⁇ _ and S AP , the dominant frequencies f M ⁇ _ and f A p being calculated by the search module of a dominant frequency MRFD, by sliding window.
  • FIG. 5 represents, in the case of FIGS. 3 and 4, the calculation by the MD detection module from the ratio of the dominant frequencies f M ⁇ _ and f AP .
  • the system detects a walking activity between the instants corresponding to the initial instant 0 s, and the instant corresponding to 182 s after the initial instant, and a walking activity starting from the instant corresponding to 221 s after the initial moment.
  • a user wears a gait detection system according to one aspect of the invention, with which it occupies different postures, immobile or moving, during different tests.
  • the measurements are made at a sampling rate of 200 Hz. These data are grouped together on a sliding window, with a duration equal to 10 s, with an overlap of 90% between two consecutive windows.
  • Bandpass filtering [0.1 Hz; 10 Hz] is applied to these measurements by a Butterworth NR filter of order 4.
  • a spectral analysis of each window is performed by calculating the square of the Fourier transform module of the product between the signal measured by the apodization window, to achieve a spectrogram. The dominant frequency f M ⁇ _ on the second axis is determined on each window.
  • the dominant frequency is determined in a respective preferred frequency value range: f M ⁇ _ between 0.25 Hz and 1 Hz, and f A p between f ML +0.25 and 2 Hz.
  • Figures 6a and 6b illustrate a first example.
  • Figure 6a illustrates a registration with a system according to an aspect of the invention worn on the belt. The detection is activated regardless of the power of the signal measured along the medio-lateral axis ML.
  • FIG. 6a shows dominant frequencies f M ⁇ _ and f A p as a function of the indexes of windows. These are the dominant frequencies determined, for each time window, respectively along the medio-lateral axes ML and anterior-posterior AP.
  • FIG. 6b represents the ratio or ratio, for each time window, between the dominant frequencies f A p and f M ⁇ _- In this example, the person only walks between the time windows 160 and 210.
  • the ratio corresponding to these time windows is around the value 2.
  • This test therefore makes it possible to determine a threshold, substantially equal to 2, in this case, for example 1.9, above which the person is considered to walk.
  • This threshold can be determined manually, according to this type of test, or by known statistical analysis techniques, to estimate the risks of false positives and false negatives.
  • the threshold is substantially equal to 2, ie close to 2, but not strictly equal to 2, an adjustment that can be made during experimental tests.
  • This adjustment can be manual or automatically developed, for example by determining a statistical distribution of the ratio between f A p and f M ⁇ _ and by estimating certain parameters of this distribution, for example the mean and the standard deviation in the case where the distribution is assumed normal.
  • Figures 7a, 7b and 7c illustrate a second example in which the gait detection system is worn on the belt.
  • a threshold the power of the measured signal is imposed, for example on the signal measured along the medio-lateral axis ML.
  • This power is represented in figure 7a of the power as a function of the window index.
  • the power unit here is the gravity constant squared This curve thus represents the power of the dominant frequency determined, along the medio-lateral axis ML, for each time window.
  • FIG. 7b only the dominant frequencies f A p along the antero-posterior axis AP are reported for time windows having a signal measured along the medio-lateral axis ML, the power of which is greater than the threshold mentioned.
  • the user walks between the time windows 155 and 210, as well as between the time windows 102 and 107.
  • FIG. 7c for each window corresponding to a step of the user, a substantially equal ratio is obtained. at 2, that is to say between 1.8 and 2.2.
  • the threshold could be set at 1 .8 or 1 .9.
  • the power criterion applies either to the signal measured along the medio-lateral axis ML, or to the signal measured along the anteroposterior axis AP, or to these two signals, the thresholds then being different.
  • FIGS. 8a and 8b illustrate a third example for which FIG. 8b represents the ratio of the dominant frequency of a Euclidean norm of the vector of measurements transmitted by said sensor CM and the dominant frequency f M ⁇ _ of the signal of the second measurement axis.
  • FIGS. 8a and 8b illustrate a third example for which FIG. 8b represents the ratio of the dominant frequency of a Euclidean norm of the vector of measurements transmitted by said sensor CM and the dominant frequency f M ⁇ _ of the signal of the second measurement axis.
  • Two other embodiments respectively illustrated in Figures 9a, 9b and 10a, 10b, with a system respectively fixed to the belt and the torso.
  • the present invention allows, at reduced cost, to detect with great precision, a walking activity of a person.
  • the present invention has particularly described the detection of a walking phase, it can be applied to a phase of the frequency ranges of search for a dominant frequency are then adjusted.
  • the present invention operates without necessarily requiring physical calibration of the motion sensor.

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Abstract

The invention relates to a system for detecting the walk of a person, provided with a housing (BT) including an at least biaxial motion sensor (CM), said housing being suitable for being attached to the upper part of the body of said person such that a first axis of measurement of said sensor (CM) coincides with the anteroposterior axis (AP) or the vertical axis (VT) of said body, and that a second axis of measurement of said sensor (CM) coincides with the medio-lateral axis (ML) of said body, said system additionally being provided with a means (MA) for analysing the measurements output by said sensor (CM), wherein said analysis means (MA) includes: a means (MT) for processing the measurement signals output by said sensor (CM) during a window of time, including a means for searching for a dominant frequency (MRFD) in said signals; and a means for detecting (MD) the walk of the person when a ratio between the dominant frequency of the signal of the first axis of measurement and the dominant frequency of said second axis of measurement, or between the dominant frequency of a Euclidean norm of the vector of measurements transmitted by said sensor (CM) and the dominant frequency of the signal of the second axis of measurement, is substantially equal to two.

Description

SYSTEME ET PROCEDE DE DETECTION DE MARCHE D'UNE PERSONNE SYSTEM AND METHOD FOR DETECTING THE MARKET OF A PERSON

L'invention porte sur un système et un procédé de détection de marche d'une personne, ou, en d'autres termes de la détection d'un déplacement d'une personne par un mode de locomotion constitué par une suite de pas.The invention relates to a system and method for detecting the walking of a person, or in other words the detection of a displacement of a person by a mode of locomotion constituted by a sequence of steps.

Des systèmes d'analyse de mouvement de personnes sont de plus en plus répandus dans le domaine biomédical, notamment pour analyser l'activité physique d'une personne.Systems of movement analysis of people are increasingly popular in the biomedical field, especially to analyze the physical activity of a person.

La détection de l'activité de marche d'une personne est une information qui permet, par exemple, d'estimer une dépense énergétique d'une personne, d'évaluer un niveau de sédentarité d'une personne, ou d'estimer la qualité ou la perte de capacité fonctionnelle après une intervention chirurgicale ou un traitement médicamenteux.The detection of a person's walking activity is information that makes it possible, for example, to estimate a person's energy expenditure, to evaluate a person's sedentary level, or to estimate the quality of a person's energy expenditure. or loss of functional ability after surgery or drug therapy.

Le document "Ambulatory System for human motion analysis using a kinematic sensor: monitoring of daily physical activity in the elderly," Biomédical Engineering, IEEE Transactions on, vol.50, no.6, pp.711-723, June 2003, de Najafi, B., Aminian, K., Paraschiv-lonescu A., Loew, F., BuIa CJ. , et Robert, P., décrit un capteur de mouvement 2A1 G (accéléromètre biaxial et gyromètre monoaxial porté sur le tronc d'une personne et dont le signal d'accélération verticale est filtré par un filtre passe-bande 0.62-5.00 Hz. Sur ce signal filtré, est recherché au moins trois occurrences régulièrement espacées de pic d'amplitude supérieure à un seuil. Il est difficile de fixer un seuil universel à priori, ce qui implique notamment un manque de fiabilité d'un tel système.The document "Ambulatory System for human motion analysis using a kinematic sensor: monitoring of daily physical activity in the elderly," Biomedical Engineering, IEEE Transactions on, vol.50, no.6, pp.711-723, June 2003, Najafi , B., Aminian, K., Paraschiv-lonescu A., Loew, F., Buia CJ. , and Robert, P., describes a 2A1 G motion sensor (biaxial accelerometer and monoaxial gyrometer worn on the trunk of a person and whose vertical acceleration signal is filtered by a 0.62-5.00 Hz bandpass filter. this filtered signal is searched for at least three regularly spaced occurrences of amplitude peak greater than a threshold It is difficult to set a universal threshold a priori, which implies in particular a lack of reliability of such a system.

Le document "Référence data for normal subjects obtained with an accelerometric device", Gait & Posture, October 2002 Vol. 16, Issue 2, Pages 124-134, de Bernard Auvinet, Gilles Berrut, Claude Touzard, Laurent Moutel, Nadine Collet, Denis Chaleil, et Eric Barrey, décrit une analyse fréquentielle d'une activité de marche considérée comme une activité sensiblement périodique, qui crée un pic de puissance à une fréquence qui dépend de la vitesse de marche. L'étude du rapport entre des harmoniques paires et impaires du signal d'accélération verticaleThe document "Reference data for normal subjects obtained with an accelerometric device", Gait & Posture, October 2002 Vol. 16, Issue 2, Pages 124-134 by Bernard Auvinet, Gilles Berrut, Claude Touzard, Laurent Moutel, Nadine Collet, Denis Chaleil, and Eric Barrey, describe a frequency analysis of a walking activity considered as a substantially periodic activity, which creates a power peak at a frequency that depends on the speed of operation. The study of the ratio between even and odd harmonics of the vertical acceleration signal

FEUILLE DE REMPLACEMENT (RÈGLE 26) permet d'étudier la stabilité de la marche. Il ne s'agit pas ici de détecter une activité de marche, mais d'analyser ou caractériser une activité de marche d'une personne dont on sait déjà qu'elle marche.SUBSTITUTE SHEET (RULE 26) allows to study the stability of walking. It is not a question here of detecting a walking activity, but of analyzing or characterizing a walking activity of a person who is already known to be walking.

Le document "Classification of waist-acceleration signais in a continuous walking record", Médical Engineering & Physics 22 (4) (2000), pp. 285-291 , de M. Sekine, T. Tamura, T. Togawa et Y. Fukui, décrit l'utilisation d'une transformée en ondelettes pour distinguer, dans un signal représentatif de la marche d'une personne, si cette dernière marche sur une surface horizontale, en montée d'escaliers ou en descente d'escaliers. Le contenu de ce document ne permet pas de détecter une activité de marche.The document "Classification of Waist-Acceleration Signals in a Continuous Walking Record", Medical Engineering & Physics 22 (4) (2000), pp. 285-291, M. Sekine, T. Tamura, T. Togawa and Y. Fukui, describes the use of a wavelet transform to distinguish, in a signal representative of a person's walk, whether the latter is walking. on a horizontal surface, climbing stairs or going down stairs. The contents of this document do not detect a walking activity.

La présente invention a pour but de détecter des activités de marche d'une personne dans un enregistrement de signaux ambulatoires de celle-ci. Selon un aspect de l'invention, il est proposé un système de détection de marche d'une personne, muni d'un boîtier comprenant un capteur de mouvement biaxial ou triaxial. Le boîtier est adapté pour être fixé sur la partie supérieure du corps de ladite personne, de manière qu'un premier axe de mesure dudit capteur coïncide avec l'axe antéro-postérieur ou l'axe vertical dudit corps et qu'un deuxième axe de mesure dudit capteur coïncide avec l'axe médio-latéral dudit corps, ledit système étant, en outre, muni de moyens d'analyse des mesures délivrées par ledit capteur. Lesdits moyens d'analyse comprennent :The present invention aims to detect walking activities of a person in an ambulatory signal recording thereof. According to one aspect of the invention, there is provided a gait detection system of a person, provided with a housing comprising a biaxial or triaxial motion sensor. The housing is adapted to be fixed on the upper part of the body of said person, so that a first measurement axis of said sensor coincides with the anteroposterior axis or the vertical axis of said body and a second axis of measurement of said sensor coincides with the medio-lateral axis of said body, said system being, furthermore, provided with means for analyzing the measurements delivered by said sensor. Said analysis means comprise:

- des moyens de traitement sur une fenêtre temporelle des signaux de mesure délivrés par ledit capteur, comprenant des moyens de recherche d'une fréquence dominante dans lesdits signaux, etmeans for processing, over a time window, measurement signals delivered by said sensor, comprising means for searching for a dominant frequency in said signals, and

- des moyens de détection de la marche de la personne lorsqu'un rapport entre la fréquence dominante du signal du premier axe de mesure et la fréquence dominante du deuxième axe de mesure, ou entre la fréquence dominante d'une norme euclidienne du vecteur de mesures transmis par ledit capteur et la fréquence dominante du signal du deuxième axe de mesure, est sensiblement égal à deux.means for detecting the gait 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 Euclidean norm of the measurement vector transmitted by said sensor and the dominant frequency of the signal of the second measurement axis, is substantially equal to two.

Un tel système permet à coût réduit, et de manière peu gênante pour la personne qui le porte, de détecter la marche d'une personne, de manière robuste et automatique. Par exemple, la fenêtre temporelle est une fenêtre glissante.Such a system makes it possible for the wearer to detect the walking of a person in a robust and automatic manner at a reduced cost, and in a manner that is not very annoying for the person wearing it. For example, the time window is a slippery window.

Ainsi le système est de grande précision, même sur une durée de traitement importante.Thus the system is highly accurate, even over a long processing time.

Dans un mode de réalisation, ledit capteur de mouvement étant triaxial, le premier axe de mesure dudit capteur coïncide avec l'axe antéro- postéheur dudit corps, le deuxième axe de mesure dudit capteur coïncide avec l'axe médio-latéral dudit corps, et le troisième axe de mesure dudit capteur coïncide avec l'axe vertical dudit corps, lesdits moyens de détection sont adaptés pour détecter un rapport sensiblement égal à deux, entre la fréquence dominante du signal du premier axe de mesure et la fréquence dominante du deuxième axe de mesure, ou entre la fréquence dominante du signal du troisième axe de mesure et la fréquence dominante du deuxième axe de mesure, ou entre la fréquence dominante d'une norme euclidienne du vecteur de mesures transmis par ledit capteur et la fréquence dominante du signal du deuxième axe de mesure.In one embodiment, said motion sensor being 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 adapted to detect 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 axis of measuring, 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 Euclidean norm of the measurement vector transmitted by said sensor and the dominant frequency of the signal of the second measuring axis.

Ainsi, la précision de la détection est améliorée.Thus, the accuracy of the detection is improved.

Selon un mode de réalisation, le système comprend, en outre, des filtres passe-haut.According to one embodiment, the system further comprises high-pass filters.

Les composantes continues respectives des signaux transmis par le capteur de mouvement sont ainsi supprimées, pour pouvoir détecter avec grande précision la fréquence dominante.The respective continuous components of the signals transmitted by the motion sensor are thus suppressed, so that the dominant frequency can be accurately detected.

Dans un mode de réalisation, le système comprend, en outre, des filtres passe-bande, par exemple de bande de fréquences comprises entre 0,5 et 10 Hz. L'influence de bruits ou fréquences de signaux sans rapport avec la marche est ainsi fortement limitée.In one embodiment, the system further comprises band-pass filters, for example of frequency band between 0.5 and 10 Hz. The influence of noises or frequencies of signals unrelated to gait is thus strongly limited.

Selon un mode de réalisation, lesdits moyens d'analyse sont internes ou externes audit boîtier, et ledit capteur de mouvement comprend des moyens de transmission avec ou sans fil pour transmettre ses mesures auxdits moyens d'analyse.According to one embodiment, said analysis means are internal or external to said housing, and said motion sensor comprises wired or wireless transmission means for transmitting its measurements to said analysis means.

Les moyens d'analyse peuvent être intégrés au boîtier ou implantés sur une base distante, et les signaux de sortie du boîtier, analysés ou non, peuvent être transmis avec ou sans fil. Ledit capteur de mouvement peut être un accéléromètre biaxial ou triaxial, un magnétomètre biaxial ou triaxial, ou un gyromètre biaxial ou triaxial.The analysis means can be integrated in the housing or located on a remote basis, and the output signals of the housing, analyzed or not, can be transmitted with or without wire. Said motion sensor may be a biaxial or triaxial accelerometer, a biaxial or triaxial magnetometer, or a biaxial or triaxial gyro.

L'invention fonctionne avec tous ces types de capteurs de mouvement.The invention works with all these types of motion sensors.

Par exemple, la fenêtre temporelle glissante a une durée de cinq secondes, avec un recouvrement partiel de quatre secondes entre deux fenêtres consécutives décalées d'une seconde.For example, the sliding time window has a duration of five seconds, with a partial overlap of four seconds between two consecutive windows shifted by one second.

Ces valeurs sont particulièrement bien adaptées à la marche d'une personne.These values are particularly well suited to a person's walk.

Selon un mode de réalisation, lesdits moyens de recherche d'une fréquence dominante pour les signaux transmis par le capteur de mouvement sont adaptés pour effectuer la recherche de fréquence dominante, dans chaque fenêtre temporelle, par analyse spectrale. Par exemple, cette analyse spectrale peut être de type spectrogramme.According to one embodiment, said search means of a dominant frequency for the signals transmitted by the motion sensor are adapted to perform the dominant frequency search, in each time window, by spectral analysis. For example, this spectral analysis may be of the spectrogram type.

Le spectrogramme, qui utilise le carré du module de la transformée de Fourrier du signal convolué à une fenêtre d'apodisation, est une façon simple, fiable, et de coût réduit permettant de rechercher une fréquence dominante, c'est-à-dire la fréquence correspondant à la puissance de signal maximum.The spectrogram, which uses the square of the Fourier transform module of the convolved signal to an apodization window, is a simple, reliable, and low-cost way of searching for a dominant frequency, ie the frequency corresponding to the maximum signal power.

Lesdits moyens de recherche d'une fréquence dominante peuvent être adaptés pour limiter la recherche d'une fréquence dominante VML selon le deuxième axe à des fréquences comprises entre 0,25 Hz et 1 Hz. Lesdits moyens de recherche d'une fréquence dominante peuvent être adaptés pour limiter la recherche d'une fréquence dominante selon le premier axe, lorsque celui-ci coïncide avec l'axe antéro- postéheur, à des fréquences comprises dans une plage prédéterminée de fréquences. Cette plage fréquentielle peut être bornée par la fréquence dominante selon le deuxième axe fMι_ Hz augmentée de 0.2 Hz et 3 Hz ([fML+0.2 ; 3]).Said search means of a dominant frequency can be adapted to limit the search for a VML dominant frequency according to the second axis at frequencies between 0.25 Hz and 1 Hz. Said search means of a dominant frequency can be adapted to limit the search for a dominant frequency along the first axis, when it coincides with the antero-hitch-hopping axis, at frequencies within a predetermined range of frequencies. This frequency range can be limited by the dominant frequency along the second axis f M ι_ Hz increased by 0.2 Hz and 3 Hz ([f ML +0.2; 3]).

De façon préférée, cette plage peut être bornée par la fréquence dominante selon le deuxième axe fMι_ Hz augmentée de 0.25 Hz et 2 Hz, ([fML+0.25 ; 2]). Lesdits moyens de recherche d'une fréquence dominante peuvent être adaptés pour limiter la recherche d'une fréquence dominante selon le premier axe, lorsque celui-ci coïncide avec l'axe vertical, à des fréquences comprises dans une plage prédéterminée de fréquences. Cette plage fréquentielle peut être bornée par la fréquence dominante selon le deuxième axe fMι_ Hz augmentée de 0.2 Hz et 3 Hz ([fMι_+0.2 ; 3]).Preferably, this range may be bounded by the dominant frequency along the second axis f M ι_ Hz increased by 0.25 Hz and 2 Hz, ([f ML +0.25; 2]). Said search means of a dominant frequency can be adapted to limit the search for a dominant frequency along the first axis, when it coincides with the vertical axis, at frequencies within a predetermined range of frequencies. This frequency range can be limited by the dominant frequency along the second axis f M ι_ Hz increased by 0.2 Hz and 3 Hz ([f M ι_ + 0.2; 3]).

Lesdits moyens de recherche d'une fréquence dominante peuvent être adaptés pour limiter la recherche d'une fréquence dominante pour la norme euclidienne du vecteur de mesures transmis par ledit capteur de mouvement, à des fréquences comprises dans une plage prédéterminée de fréquences. Cette plage fréquentielle peut être bornée par la fréquence dominante selon le deuxième axe fMι_ Hz augmentée de 0.2 Hz et 3 Hz ([fML+0.2 ; 3]).Said search means of a dominant frequency can be adapted to limit the search for a dominant frequency for the Euclidean standard of the measurement vector transmitted by said motion sensor, at frequencies within a predetermined range of frequencies. This frequency range can be limited by the dominant frequency along the second axis f M ι_ Hz increased by 0.2 Hz and 3 Hz ([f ML +0.2; 3]).

L'ensemble de ces valeurs sont particulièrement bien adaptées à l'activité de marche.All of these values are particularly well suited to walking activity.

Selon un mode de réalisation, lesdits moyens de détection sont adaptés pour détecter un rapport desdites fréquences dominantes sensiblement égal à deux, à une précision près, lorsqu'en outre, au moins sur un axe, la puissance du signal, à au moins une fréquence, est supérieure à un seuil.According to one embodiment, said detection means are adapted to detect a ratio of said dominant frequencies substantially equal to two, to a precision, when, moreover, at least on one axis, the power of the signal, at least one frequency , is greater than a threshold.

Autrement dit, on ne détermine un tel rapport, ou on ne l'exploite, que pour les fenêtres présentant, sur au moins un axe, au moins une fréquence dont la puissance est supérieure à seuil déterminé, ce seuil pouvant être appelé seuil de puissance. Ce seuil de puissance est déterminé à priori, ou ajusté expérimentalement, par exemple lors d'une phase d'essais.In other words, such a ratio is determined or exploited only for windows having, on at least one axis, at least one frequency whose power is greater than a determined threshold, this threshold possibly being called a power threshold. . This power threshold is determined a priori, or adjusted experimentally, for example during a test phase.

On peut appliquer cette condition de puissance d'au moins une fréquence à au moins un axe, mais également à tous les axes. Précisons que lorsque cette condition de puissance est appliquée sur différents axes, chaque seuil de puissance peut être différent l'un de l'autre.This power condition of at least one frequency can be applied to at least one axis, but also to all axes. Note that when this power condition is applied on different axes, each power threshold may be different from each other.

Selon un mode de réalisation particulier, lesdits moyens de détermination sont adaptés pour déterminer le rapport des fréquences dominantes, correspondant à une fenêtre temporelle donnée, lorsque, sur au moins un axe, la fréquence dominante a une puissance supérieure à une puissance seuil. On peut appliquer cette condition de seuil uniquement à la fréquence dominante, mais également à d'autres fréquences ou bandes de fréquence définies.According to a particular embodiment, said determination means are adapted to determine the ratio of the dominant frequencies, corresponding to a given time window, when, on at least one axis, the dominant frequency has a power greater than a threshold power. This threshold condition can be applied only to the dominant frequency, but also to other defined frequencies or frequency bands.

Précisons que ce critère de seuil en puissance peut également s'appliquer à la norme euclidienne du vecteur de mesures. Pour chaque fenêtre temporelle, on vérifiera alors la ou les fréquences, par exemple la fréquence dominante, ont une puissance supérieure à un seuil de puissance.Note that this threshold power criterion can also be applied to the Euclidean norm of the vector of measurements. For each time window, then check the frequency or frequencies, for example the dominant frequency, have a power greater than a power threshold.

Ce seuil en puissance peut être fixé à priori ou en déterminant au préalable une puissance dans un intervalle de temps durant lequel il ne se passe rien, par exemple durant le calibrage anatomique.This power threshold can be fixed a priori or by previously determining a power in a time interval during which nothing happens, for example during anatomical calibration.

Selon un mode de réalisation, ledit boîtier est adapté pour être fixé sur le torse ou sur le sacrum de ladite personne.According to one embodiment, said housing is adapted to be fixed on the torso or on the sacrum of said person.

Lorsque le boîtier est fixé au niveau du torse, l'amplitude des oscillations du tronc est plus élevée, ce qui améliore la précision du système.When the housing is attached to the torso, the amplitude of the oscillations of the trunk is higher, which improves the accuracy of the system.

La fixation au niveau du sacrum est particulièrement facile et discrète, par exemple au moyen d'une ceinture.The fixation at the level of the sacrum is particularly easy and discreet, for example by means of a belt.

Selon un autre aspect de l'invention, il est également proposé un procédé de détection de marche d'une personne, à partir de mesures effectuées par un capteur de mouvement biaxial ou triaxial, de mouvements selon un premier axe de mesure dudit capteur coïncidant avec l'axe antéro-postérieur ou l'axe vertical du corps de ladite personne et selon un deuxième axe mesure dudit capteur coïncidant avec l'axe médio-latéral dudit corps, dans lequel :According to another aspect of the invention, there is also provided a method for detecting a person's walking, from measurements made by a biaxial or triaxial motion sensor, of movements along a first measurement axis of said sensor coinciding with the anteroposterior axis or the vertical axis of the body of said person and along a second axis measuring said sensor coinciding with the medio-lateral axis of said body, in which:

- on traite, sur une fenêtre temporelle, les signaux de mesure délivrés par ledit capteur de mouvement, ledit traitement comprenant une recherche d'une fréquence dominante dans lesdits signaux etthe measurement signals delivered by said motion sensor are processed over a time window, said processing comprising a search for a dominant frequency in said signals and

- on détecte la marche de ladite personne lorsqu'un rapport entre la fréquence dominante du signal du premier axe de mesure et la fréquence dominante du deuxième axe de mesure, ou entre la fréquence dominante d'une norme euclidienne du vecteur de mesures transmis par ledit capteur et la fréquence dominante du signal du deuxième axe de mesure, est sensiblement égal à deux. Par exemple, le traitement est effectué sur une fenêtre temporelle glissante.the step 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 Euclidean 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. For example, the processing is performed on a sliding time window.

L'invention sera mieux comprise à l'étude de quelques modes de réalisation décrits à titre d'exemples nullement limitatifs et illustrés par les dessins annexés sur lesquels :The invention will be better understood by studying a few embodiments described by way of non-limiting examples and illustrated by the appended drawings in which:

- la figure 1 illustre schématiquement un mode de réalisation d'un système, selon un aspect de l'invention ;- Figure 1 schematically illustrates an embodiment of a system, according to one aspect of the invention;

- la figure 2 représente schématiquement une personne et ses axes anatomiques, antéro-postérieur, vertical et médio-latéral ; - la figure 3 illustre un exemple de mesures faites par un système selon la figure 1 , dans lequel le capteur de mouvement est un accéléromètre biaxial ;- Figure 2 schematically shows a person and its anatomical axes, anteroposterior, vertical and medio-lateral; FIG. 3 illustrates an example of measurements made by a system according to FIG. 1, in which the motion sensor is a biaxial accelerometer;

- les figures 4 et 5 illustrent le fonctionnement des moyens d'analyse ; - les figures 6a et 6b illustrent un premier mode de mise en œuvre du système selon un aspect de l'invention ;FIGS. 4 and 5 illustrate the operation of the analysis means; FIGS. 6a and 6b illustrate a first mode of implementation of the system according to one aspect of the invention;

- les figures 7a, 7b et 7c illustrent un deuxième mode de mise en œuvre du système selon un aspect de l'invention ;FIGS. 7a, 7b and 7c illustrate a second mode of implementation of the system according to one aspect of the invention;

- les figures 8a et 8b illustrent un troisième mode de mise en œuvre du système selon un aspect de l'invention ;FIGS. 8a and 8b illustrate a third mode of implementation of the system according to one aspect of the invention;

- les figures 9a et 9b illustrent un quatrième mode de mise en œuvre du système selon un aspect de l'invention ; etFIGS. 9a and 9b illustrate a fourth mode of implementation of the system according to one aspect of the invention; and

- les figures 10a et 10b illustrent un cinquième mode de mise en œuvre du système selon un aspect de l'invention. Dans l'ensemble de figures, les éléments ayants les mêmes références sont similaires.FIGS. 10a and 10b illustrate a fifth mode of implementation of the system according to one aspect of the invention. In the set of figures, the elements having the same references are similar.

Tel qu'illustré sur la figure 1 , le système de détection de marche d'une personne comprend un boîtier BT comprenant un capteur de mouvement CM biaxial ou triaxial. Le boîtier BT est adapté pour être fixé sur la partie supérieure du corps de ladite personne, en l'occurrence au moyen d'une ceinture élastique de fixation CEF, de sorte qu'un premier axe de mesure dudit capteur de mouvement coïncide avec l'axe antéro- postérieur AP ou l'axe vertical VT dudit corps et qu'un deuxième axe de mesure dudit capteur de mouvement coïncide avec l'axe médio-latéral ML dudit corps. En variante, tout autre moyen de fixation peut convenir. Cette mise en coïncidence peut, par exemple, être faite par calibration anatomique, par exemple en demandant à la personne à laquelle le boîtier BT a été fixé de se tenir le plus droit possible pendant quelques secondes contre un mur, le système, de manière connue, détermine la matrice de rotation à appliquer aux mesures pour délivrer des mesures ramenées aux axes médio-latéral ML, antéro-postérieur AP ou vertical VT. Le capteur de mouvement est CM est également pourvu d'un module de transmission MTR pour transmettre les mesures, sur cet exemple par transmission sans fil, à une station externe SE, en l'espèce un ordinateur portable.As illustrated in FIG. 1, a person's walking detection system comprises a BT housing comprising a biaxial or triaxial CM motion sensor. The housing BT is adapted to be fixed on the upper part of the body of said person, in this case by means of a resilient fastening belt CEF, so that a first measurement axis of said motion sensor coincides with the anterior-posterior axis AP or the vertical axis VT of said body and a second measurement axis of said motion sensor coincides with the medio-lateral axis ML of said body. Alternatively, any other means of attachment may be suitable. This coincidence can, for example, be made by anatomical calibration, for example by asking the person to whom the BT housing was fixed to stand as straight as possible for a few seconds against a wall, the system, in a known manner , determines the rotation matrix to be applied to the measurements to deliver measurements brought back to the medio-lateral axes ML, anteroposterior AP or vertical VT. The motion sensor CM is also provided with a transmission module MTR for transmitting the measurements, in this example by wireless transmission, to an external station SE, in this case a laptop.

En variante, la transmission pourrait être filaire. Le capteur de mouvement peut, par exemple être un accéléromètre biaxial ou triaxial, un magnétomètre biaxial ou triaxial, ou un gyromètre biaxial ou triaxial.Alternatively, the transmission could be wired. The motion sensor may, for example, be a biaxial or triaxial accelerometer, a biaxial or triaxial magnetometer, or a biaxial or triaxial gyro.

Toutefois, dans la suite de la description, de manière non limitative, le capteur de mouvement CM sera un accéléromètre biaxial dont le premier axe de mesure coïncide avec l'axe antéro-postérieur AP du corps de la personne, et le deuxième axe de mesure coïncide avec l'axe médio-latéral ML du corps de la personne.However, in the remainder of the description, in a nonlimiting manner, the motion sensor CM will be a biaxial accelerometer whose first measurement axis coincides with the anteroposterior axis AP of the body of the person, and the second axis of measurement coincides with the medial-lateral axis ML of the body of the person.

En variante, le deuxième axe de mesure de l'accéléromètre peut coïncider avec l'axe médio-latéral ML du corps de la personne, et le premier axe de mesure peut coïncider avec l'axe vertical VT du corps de la personne.Alternatively, the second measurement axis of the accelerometer may coincide with the medial-lateral axis ML of the body of the person, and the first measurement axis may coincide with the vertical axis VT of the body of the person.

L'ordinateur portable SE comprend un module d'analyse MA des données transmises par l'accéléromètre CM. En variante, le module d'analyse peut être intégré au boîtier BT.The portable computer SE comprises an analysis module MA of the data transmitted by the accelerometer CM. Alternatively, the analysis module can be integrated into the LV box.

Le module d'analyse est adapté pour échantillonner les signaux reçus de l'accéléromètre CM à une fréquence d'échantillonnage inférieure ou égale à 1 kHz, et typiquement de l'ordre de 10 à 200 Hz.The analysis module is adapted to sample the signals received from the accelerometer CM at a sampling frequency less than or equal to 1 kHz, and typically of the order of 10 to 200 Hz.

Le module d'analyse MA comprend un module de traitement MT pour traiter les signaux de mesure délivrés par l'accéléromètre CM.The analysis module MA comprises a processing module MT for processing the measurement signals delivered by the accelerometer CM.

En variante, dans le cas d'un capteur de mouvement triaxialAlternatively, in the case of a triaxial motion sensor

CM, tel un accéléromètre triaxial, il est possible d'effectuer une calibration anatomique de manière à ce que le premier axe de mesure de l'accéléromètre coïncide avec l'axe antéro-postérieur AP du corps de la personne, le deuxième axe de mesure de l'accéléromètre coïncide avec l'axe médio-latéral ML du corps de la personne, et le troisième axe de mesure de l'accéléromètre coïncide avec l'axe vertical VT du corps de la personne. En ce cas, le module de détection est adapté pour détecter un rapport sensiblement égal à deux, entre la fréquence dominante du signal du premier axe de mesure et la fréquence dominante du deuxième axe de mesure, ou entre la fréquence dominante du signal du troisième axe de mesure et la fréquence dominante du deuxième axe de mesure, ou entre la fréquence dominante d'une norme euclidienne du vecteur de mesures transmis par ledit capteur et la fréquence dominante du signal du deuxième axe de mesure. On a alors une précision de détection améliorée.CM, such as a triaxial accelerometer, it is possible to perform an anatomical calibration so that the first axis of measurement of the accelerometer coincides with the anteroposterior axis AP of the body of the person, the second axis of measurement of the accelerometer coincides with the medial-lateral axis ML of the body of the person, and the third axis of measurement of the accelerometer coincides with the vertical axis VT of the body of the person. In this case, the detection module is adapted to detect 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 third axis signal. measurement and the dominant frequency of the second measurement axis, or between the dominant frequency of a Euclidean norm of the measurement vector transmitted by said sensor and the dominant frequency of the signal of the second measurement axis. We then have an improved detection precision.

On entend par un rapport ou ratio sensiblement égal à 2, un ratio par exemple compris entre 1.7 et 2.3, et de préférence entre 1.9 et 2.1. Ce ratio peut être prédéterminé, mais également ajusté expérimentalement, notamment lors d'une phase d'essais. On analyse alors précisément les différentes valeurs prises par ce ratio lorsque la personne marche, et on détermine la valeur critique qui sera ensuite mise en œuvre dans l'algorithme. Cette détermination peut notamment être effectuée statistiquement, en considérant les risques associés à des faux positifs (le dispositif signale que la personne marche alors qu'elle ne marche pas) ou à des faux négatifs (le dispositif indique que la personne ne marche pas alors qu'elle marche).By a ratio or ratio substantially equal to 2, a ratio for example between 1.7 and 2.3, and preferably between 1.9 and 2.1. This ratio can be predetermined, but also adjusted experimentally, especially during a test phase. We then analyze precisely the different values taken by this ratio when the person walks, and we determine the critical value that will be implemented in the algorithm. This determination can be made statistically, considering the risks associated with false positives (the device indicates that the person is walking when it is not working) or false negatives (the device indicates that the person does not 'she walks).

Le module de traitement MT peut comprendre des filtres passe- haut, FPH permettant de supprimer les composantes continues respectives des signaux transmis par l'accéléromètre CM, pour pouvoir détecter avec grande précision la fréquence dominante.The processing module MT may comprise high-pass filters, FPH for deleting the respective continuous components of the signals transmitted by the accelerometer CM, to be able to accurately detect the dominant frequency.

Le module de traitement MT peut comprendre également des filtres passe-bande de manière à limiter fortement l'influence de bruits ou fréquences de signaux sans rapport avec la marche.The processing module MT may also include bandpass filters so as to greatly limit the influence of noises or frequencies of signals unrelated to walking.

En outre, le module de traitement MT comprend un module de recherche d'une fréquence dominante MRFD pour les signaux transmis par le capteur de mouvement, par analyse spectrale. L'analyse spectrale, qui consiste à estimer la puissance du signal en fonction de la fréquence, est une manière connue, simple et peu coûteuse en termes de calculs pour rechercher une fréquence dominante dans un signal. On entend par fréquence dominante la fréquence qui correspond au maximum de la densité de puissance du signal. Bien sûr, en variante, toute autre manière de rechercher une fréquence dominante MRFD peut être envisagée. Par exemple, l'analyse spectrale peut être réalisée en utilisant une transformée de Fourier, mais également d'autres techniques connues de l'homme du métier, par exemple une transformée en ondelettes, technique mieux adaptée aux signaux non station naires.In addition, the processing module MT comprises a search module of a dominant frequency MRFD for the signals transmitted by the motion sensor, by spectral analysis. Spectral analysis, which consists in estimating the signal power as a function of frequency, is a known, simple and inexpensive way of calculating to search for a dominant frequency in a signal. By dominant frequency is meant the frequency which corresponds to the maximum of the power density of the signal. Of course, alternatively, any other way of searching for a dominant MRFD frequency may be considered. For example, the spectral analysis can be carried out using a Fourier transform, but also other techniques known to those skilled in the art, for example a wavelet transform, a technique better adapted to nonstationary signals.

Le module d'analyse MA comprend également un module de détection MD de la marche de la personne lorsqu'un rapport entre la fréquence dominante du signal du premier axe de mesure et la fréquence dominante du deuxième axe de mesure, ou entre la fréquence dominante d'une norme euclidienne du vecteur de mesures transmis par ledit capteur et la fréquence dominante du signal du deuxième axe de mesure, est sensiblement égal à deux.The analysis module MA also comprises a detection module MD of the step 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 the a Euclidean 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.

La présente invention fonctionne sans nécessiter de calibration physique du capteur de mouvement CM, ou, en d'autres termes, un système selon l'invention fonctionne à partir des données brutes exprimées en unité numérique ou en volts et la connaissance des gains et décalages du capteur de mouvement CM n'est pas indispensable. Si on décide de ne pas transformer les volts en unité physique (par exemple des m/s2 pour un accéléromètre) la notion de seuil minimal de puissance peut être décidée à partir d'une mesure de la personne dans un état de repos et non plus à partir d'une donnée cinématique. La figure 2 illustre schématiquement une personne, et ses trois axes anatomiques, l'axe médio-latéral ML, l'axe antéro-postéheur AP, et l'axe vertical VT, orientés de sorte que le trièdre (ML, VT, AP) soit un trièdre direct. L'axe médio-latéral ML du corps est orienté de la partie gauche du corps vers la partie droite du corps, l'axe antéro-postéheur AP est orienté de la partie arrière du corps vers la partie avant du corps et l'axe vertical est orienté de la partie supérieure du corps vers la partie inférieure du corps.The present invention operates without the need for a physical calibration of the motion sensor CM, or, in other words, a system according to the invention operates from the raw data expressed in numerical unit or in volts and the knowledge of the gains and offsets of the CM motion sensor is not essential. If we decide not to transform the volts into a physical unit (for example m / s 2 for an accelerometer) the notion of minimum power threshold can be decided from a measurement of the person in a state of rest and not more from a kinematic data. FIG. 2 diagrammatically illustrates a person, and his three anatomical axes, the medio-lateral axis ML, the anterior-posterior AP axis, and the vertical axis VT, oriented so that the trihedron (ML, VT, AP) be a direct trihedron. The medio-lateral axis ML of the body is oriented from the left part of the body to the right part of the body, the anteroposterior axis AP is oriented from the rear part of the body towards the front part of the body and the vertical axis is oriented from the upper body to the lower part of the body.

De manière optimale, le boîtier peut être disposé au niveau du torse, ou au niveau du sacrum. Le filtre passe-bande FPB peut, par exemple être un filtre de Butterworth d'ordre 4 filtrant dans la bande de fréquences comprises entre 0,5 et 10 Hz, particulièrement bien adaptée à la marche.Optimally, the housing can be disposed at the torso, or at the level of the sacrum. The band-pass filter FPB may, for example be a Butterworth filter of order 4 filtering in the frequency band between 0.5 and 10 Hz, particularly well suited to walking.

Les signaux sont découpés en fenêtres temporelles d'analyse, les fenêtres temporelles étant de préférence des fenêtres temporelles glissantes, par exemple en fenêtres de cinq secondes, avec un recouvrement partiel de quatre secondes entre deux fenêtres consécutives décalées d'une seconde. Pour chaque fenêtre temporelle, on recherche ensuite des fréquences dominantes de signaux. Le module de recherche d'une fréquence dominante MRFD par analyse spectrale de type spectrogramme peut être adapté pour limiter la recherche d'une fréquence dominante selon le premier axe fMι_ à des fréquences comprises entre 0,25 Hz et 1 Hz.The signals are divided into analysis time windows, the time windows being preferably sliding time windows, for example in five-second windows, with a partial overlap of four seconds between two consecutive windows shifted by one second. For each time window, it then seeks dominant frequencies of signals. The search module of a MRFD dominant frequency by spectral analysis of spectrogram type can be adapted to limit the search for a dominant frequency along the first axis f M ι_ at frequencies between 0.25 Hz and 1 Hz.

Le module de recherche d'une fréquence dominante MRFD par analyse spectrale peut également être adapté pour limiter la recherche d'une fréquence dominante selon le premier axe, lorsque celui-ci coïncide avec l'axe antéro-postéheur AP, à des fréquences comprises entre la fréquence dominante selon le deuxième axe fMι_ Hz augmentée de 0.2 Hz et 3 Hz, ou à des fréquences comprises entre la fréquence dominante selon le deuxième axe fMι_ Hz augmentée de 0.25 Hz et 2 Hz ([fMι_+0.25 ;The search module for a dominant frequency MRFD by spectral analysis can also be adapted to limit the search for a dominant frequency along the first axis, when it coincides with the anteroposterior axis AP, at frequencies between the dominant frequency along the second axis f M ι_ Hz increased by 0.2 Hz and 3 Hz, or at frequencies between the dominant frequency along the second axis f M ι_ Hz increased by 0.25 Hz and 2 Hz ([f M ι_ + 0.25 ;

2])-2]) -

Le module de recherche d'une fréquence dominante MRFD par analyse spectrale peut également être adapté pour limiter la recherche d'une fréquence dominante selon le premier axe, lorsque celui-ci coïncide avec l'axe vertical VT, à des fréquences comprises entre la fréquence dominante selon le deuxième axe fMι_ Hz augmentée de 0.2 Hz et 3 Hz.The search module of a dominant frequency MRFD by spectral analysis can also be adapted to limit the search for a dominant frequency along the first axis, when it coincides with the vertical axis VT, at frequencies between the frequency dominant according to the second axis f M ι_ Hz increased by 0.2 Hz and 3 Hz.

Le module de recherche d'une fréquence dominante MRFD par analyse spectrale peut également être adapté pour limiter la recherche d'une fréquence dominante pour la norme euclidienne du vecteur de mesures transmis par ledit capteur de mouvement CM, à des fréquences comprises entre la fréquence dominante selon le deuxième axe fMι_ Hz augmentée de 0.2 Hz et 3 Hz.The module for finding a MRFD dominant frequency by spectral analysis may also be adapted to limit the search for a dominant frequency for the Euclidean norm of the vector of measurements transmitted by said CM motion sensor, at frequencies between the dominant frequency along the second axis f M ι_ Hz increased by 0.2 Hz and 3 Hz.

Toutes ces limitations de recherches de fréquence dominante sont particulièrement adaptées à la marche, et permettent de limiter le temps de calcul et la taille de la mémoire utilisée. De plus, des essais ont montré que le choix de telles plages fréquentielles, dans lesquelles on limite la recherche d'une fréquence dominante, permettait d'accroître la fiabilité, voire la stabilité, en diminuant notamment les risques de faux positifs ou de faux négatifs. La figure 3 représente un exemple de signaux SMι_ et SAp transmis par un boîtier BT selon un aspect de l'invention, muni d'un accéléromètre biaxial CM, dont le premier axe de mesure coïncide avec l'axe antéro-postérieur AP, et le deuxième axe de mesure coïncide avec l'axe médio-latéral ML, en fonction du temps. Le boîtier BT est, par exemple, disposé au niveau du sacrum de la personne, dont on surveille l'activité.All these limitations of dominant frequency searches are particularly suitable for walking, and allow to limit the calculation time and the size of the memory used. In addition, tests have shown that the choice of such frequency ranges, in which the search for a dominant frequency is limited, made it possible to increase the reliability and even the stability, in particular by reducing the risks of false positives or false negatives. . FIG. 3 represents an example of signals S M 1 and S A p transmitted by a housing BT according to one aspect of the invention, provided with a biaxial accelerometer CM, whose first measurement axis coincides with the anteroposterior axis. AP, and the second measurement axis coincides with the medio-lateral axis ML, as a function of time. The BT housing is, for example, disposed at the sacrum of the person, whose activity is monitored.

La figure 4 représente, pour le cas des données de la figure 3, les fréquences dominantes fMι_ et fAp en fonction du temps, correspondant aux signaux SMι_ et SAP, les fréquences dominantes fMι_ et fAp étant calculées par le module recherche d'une fréquence dominante MRFD, par fenêtre glissante.FIG. 4 represents, for the case of the data of FIG. 3, the dominant frequencies f M ι_ and f A p as a function of time, corresponding to the signals S M ι_ and S AP , the dominant frequencies f M ι_ and f A p being calculated by the search module of a dominant frequency MRFD, by sliding window.

La figure 5 représente, pour le cas des figures 3 et 4, le calcul, par le module de détection de marche MD à partir du rapport des fréquences dominantes fMι_ et fAP. Le système détecte alors une activité de marche entre les instants correspondant à l'instant initial 0 s, et l'instant correspondant à 182 s après l'instant initial, et une activité de marche reprenant à partir de l'instant correspondant à 221 s après l'instant initial.FIG. 5 represents, in the case of FIGS. 3 and 4, the calculation by the MD detection module from the ratio of the dominant frequencies f M ι_ and f AP . The system then detects a walking activity between the instants corresponding to the initial instant 0 s, and the instant corresponding to 182 s after the initial instant, and a walking activity starting from the instant corresponding to 221 s after the initial moment.

Dans les exemples de mises en œuvre qui suivent, dans lesquels un utilisateur porte un système de détection de marche selon un aspect de l'invention, avec lequel il occupe différente postures, immobiles ou en déplacement, durant différents essais.In the examples of implementations which follow, in which a user wears a gait detection system according to one aspect of the invention, with which it occupies different postures, immobile or moving, during different tests.

Les mesures sont effectuées, en l'espèce, à une cadence d'échantillonnage de 200 Hz. Ces données sont regroupées sur une fenêtre glissante, d'une durée égale à 10 s, avec un chevauchement de 90% entre deux fenêtres consécutives. Un filtrage passe bande [0.1 Hz ; 10 Hz] est appliqué à ces mesures par un filtre NR Butterworth d'ordre 4. Une analyse spectrale de chaque fenêtre est réalisée en calculant le carré du module de la transformée de Fourier du produit entre le signal mesuré par la fenêtre d'apodisation, permettant d'aboutir à un spectrogramme. La fréquence dominante fMι_ sur le deuxième axe est déterminée, sur chaque fenêtre.In this case, the measurements are made at a sampling rate of 200 Hz. These data are grouped together on a sliding window, with a duration equal to 10 s, with an overlap of 90% between two consecutive windows. Bandpass filtering [0.1 Hz; 10 Hz] is applied to these measurements by a Butterworth NR filter of order 4. A spectral analysis of each window is performed by calculating the square of the Fourier transform module of the product between the signal measured by the apodization window, to achieve a spectrogram. The dominant frequency f M ι_ on the second axis is determined on each window.

Dans ces exemples, pour chaque axe de mesure, est déterminée la fréquence dominante dans une plage de valeurs de fréquences préférentielle respective : fMι_ entre 0.25 Hz et 1 Hz, et fAp entre fML+0.25 et 2 Hz.In these examples, for each measurement axis, the dominant frequency is determined in a respective preferred frequency value range: f M ι_ between 0.25 Hz and 1 Hz, and f A p between f ML +0.25 and 2 Hz.

Les figures 6a et 6b illustrent un premier exemple. La figure 6a illustre un enregistrement avec un système selon un aspect de l'invention porté à la ceinture. La détection est activée quelle que soit la puissance du signal mesuré selon l'axe médio-latéral ML. La figure 6a représente des fréquences dominantes fMι_ et fAp en fonction des index de fenêtres. Il s'agit des fréquences dominantes déterminées, pour chaque fenêtre temporelle, respectivement selon les axes médio-latéral ML et antéro- postéheur AP. La figure 6b représentant le ratio ou rapport, pour chaque fenêtre temporelle, entre les fréquences dominantes fAp et fMι_- Sur cet exemple, la personne ne marche qu'entre les fenêtres temporelles 160 et 210.Figures 6a and 6b illustrate a first example. Figure 6a illustrates a registration with a system according to an aspect of the invention worn on the belt. The detection is activated regardless of the power of the signal measured along the medio-lateral axis ML. FIG. 6a shows dominant frequencies f M ι_ and f A p as a function of the indexes of windows. These are the dominant frequencies determined, for each time window, respectively along the medio-lateral axes ML and anterior-posterior AP. FIG. 6b represents the ratio or ratio, for each time window, between the dominant frequencies f A p and f M ι_- In this example, the person only walks between the time windows 160 and 210.

Le ratio correspondant à ces fenêtres temporelles se situe autour de la valeur 2. Cet essai permet donc de déterminer un seuil, sensiblement égal à 2, en l'espèce, par exemple 1.9, en dessus duquel on considère que la personne marche. Ce seuil peut-être déterminé manuellement, selon ce type d'essai, ou par des techniques d'analyses statistiques connues, permettant d'estimer les risques de faux positifs et de faux négatifs.The ratio corresponding to these time windows is around the value 2. This test therefore makes it possible to determine a threshold, substantially equal to 2, in this case, for example 1.9, above which the person is considered to walk. This threshold can be determined manually, according to this type of test, or by known statistical analysis techniques, to estimate the risks of false positives and false negatives.

Il est présentement illustré que le seuil est sensiblement égal à 2, c'est à dire voisin de 2, mais pas strictement égal à 2, un ajustement pouvant être réalisé au cours d'essais expérimentaux. Cet ajustement peut-être manuel ou élaboré automatiquement, par exemple en déterminant une distribution statistique du ratio entre fAp et fMι_ et en estimant certains paramètres de cette distribution, par exemple la moyenne et l'écart type dans le cas ou la distribution est supposée normale.It is currently shown that the threshold is substantially equal to 2, ie close to 2, but not strictly equal to 2, an adjustment that can be made during experimental tests. This adjustment can be manual or automatically developed, for example by determining a statistical distribution of the ratio between f A p and f M ι_ and by estimating certain parameters of this distribution, for example the mean and the standard deviation in the case where the distribution is assumed normal.

Les figures 7a, 7b et 7c illustrent un deuxième exemple dans lequel le système de détection de marche est porté à la ceinture. Un seuil de puissance du signal mesuré est imposé, par exemple sur le signal mesuré selon l'axe médio-latéral ML. Ici, le seuil de puissance au dessous duquel on ne cherche pas à détecter un ratio fAp / ÏMI. est fixé à 0.01 g2 (g=9.81 m. s"2). Cette puissance est représentée sur la figure 7a de la puissance en fonction de l'index de fenêtre. L'unité de puissance est ici la constante de gravité au carré. Cette courbe représente donc la puissance de la fréquence dominante déterminée, selon l'axe médio-latéral ML, pour chaque fenêtre temporelle.Figures 7a, 7b and 7c illustrate a second example in which the gait detection system is worn on the belt. A threshold the power of the measured signal is imposed, for example on the signal measured along the medio-lateral axis ML. Here, the power threshold below which one does not try to detect a ratio f A p / IMI . is set at 0.01 g 2 (g = 9.81 m s s 2 ) This power is represented in figure 7a of the power as a function of the window index.The power unit here is the gravity constant squared This curve thus represents the power of the dominant frequency determined, along the medio-lateral axis ML, for each time window.

Sur la figure 7b, ne sont reportées que les fréquences dominantes fAp selon l'axe antéro-postérieur AP que pour des fenêtres temporelles présentant un signal mesuré selon l'axe médio-latéral ML, dont la puissance est supérieure au seuil mentionné. Sur cet exemple, l'utilisateur marche entre les fenêtres temporelles 155 et 210, ainsi qu'entre les fenêtres temporelles 102 et 107. Sur la figure 7c, pour chaque fenêtre correspondant à une marche de l'utilisateur, on obtient un ratio sensiblement égal à 2, c'est-à- dire compris entre 1 .8 et 2.2. En l'espèce, le seuil pourrait être fixé à 1 .8 ou 1 .9. Le critère de puissance s'applique soit au signal mesuré selon l'axe médio-latéral ML, soit au signal mesuré selon l'axe antéro-postérieur AP, soit à ces deux signaux, les seuils pouvant être alors différents.In FIG. 7b, only the dominant frequencies f A p along the antero-posterior axis AP are reported for time windows having a signal measured along the medio-lateral axis ML, the power of which is greater than the threshold mentioned. In this example, the user walks between the time windows 155 and 210, as well as between the time windows 102 and 107. In FIG. 7c, for each window corresponding to a step of the user, a substantially equal ratio is obtained. at 2, that is to say between 1.8 and 2.2. In this case, the threshold could be set at 1 .8 or 1 .9. The power criterion applies either to the signal measured along the medio-lateral axis ML, or to the signal measured along the anteroposterior axis AP, or to these two signals, the thresholds then being different.

Les figures 8a et 8b illustrent un troisième exemple pour lequel la figure 8b représente le ratio de la fréquence dominante d'une norme euclidienne du vecteur de mesures transmis par ledit capteur CM et la fréquence dominante fMι_ du signal du deuxième axe de mesure. Deux autres exemples de réalisation illustrés respectivement sur les figures 9a, 9b et 10a, 10b, avec un système fixé respectivement à la ceinture et au torse.FIGS. 8a and 8b illustrate a third example for which FIG. 8b represents the ratio of the dominant frequency of a Euclidean norm of the vector of measurements transmitted by said sensor CM and the dominant frequency f M ι_ of the signal of the second measurement axis. Two other embodiments respectively illustrated in Figures 9a, 9b and 10a, 10b, with a system respectively fixed to the belt and the torso.

Ces exemples mettent en évidence que l'utilisateur marche entre les fenêtres temporelles 150 et 200. Il est particulièrement bien illustré sur ces deux exemples, qu'où que soit placé le système sur la partie supérieure du corps, le système est d'une grande fiabilité.These examples highlight that the user walks between the time slots 150 and 200. It is particularly well illustrated on these two examples, that wherever the system is placed on the upper part of the body, the system is of great reliability.

La présente invention permet, à coût réduit, de détecter avec une grande précision, une activité de marche d'une personne.The present invention allows, at reduced cost, to detect with great precision, a walking activity of a person.

Bien que la présente invention ait particulièrement décrit la détection d'une phase de marche, elle peut être appliquée à une phase de course, les plages fréquentielles de recherche d'une fréquence dominante étant alors ajustées.Although the present invention has particularly described the detection of a walking phase, it can be applied to a phase of the frequency ranges of search for a dominant frequency are then adjusted.

En outre, la présente invention fonctionne sans nécessiter obligatoirement de calibration physique du capteur de mouvement. In addition, the present invention operates without necessarily requiring physical calibration of the motion sensor.

Claims

REVENDICATIONS 1. Système de détection de marche d'une personne, muni d'un boîtier (BT) comprenant un capteur de mouvement (CM) au moins biaxial, ledit boîtier étant adapté pour être fixé sur la partie supérieure du corps de ladite personne, de manière qu'un premier axe de mesure dudit capteur (CM) coïncide avec l'axe antéro-postéheur (AP) ou l'axe vertical (VT) dudit corps et qu'un deuxième axe de mesure dudit capteur (CM) coïncide avec l'axe médio-latéral (ML) dudit corps, ledit système étant, en outre, muni de moyens d'analyse (MA) des mesures délivrées par ledit capteur (CM), caractérisé en ce que lesdits moyens d'analyse (MA) comprennent :A gait detection system of a person, provided with a housing (BT) comprising a motion sensor (CM) at least biaxially, said housing being adapted to be fixed on the upper part of the body of said person, of in that a first measurement axis of said sensor (CM) coincides with the anteroposterh axis (AP) or the vertical axis (VT) of said body and that a second measurement axis of said sensor (CM) coincides with the medio-lateral axis (ML) of said body, said system being, furthermore, provided with means of analysis (MA) of measurements delivered by said sensor (CM), characterized in that said analysis means (MA) comprise : - des moyens de traitement (MT) sur une fenêtre temporelle des signaux de mesure délivrés par ledit capteur (CM), comprenant des moyens de recherche d'une fréquence dominante (MRFD) dans lesdits signaux, etprocessing means (MT) over a time window of the measurement signals delivered by said sensor (CM), comprising means for searching for a dominant frequency (MRFD) in said signals, and - des moyens de détection (MD) de la marche de la personne lorsqu'un rapport entre la fréquence dominante du signal du premier axe de mesure et la fréquence dominante du deuxième axe de mesure, ou entre la fréquence dominante d'une norme euclidienne du vecteur de mesures transmis par ledit capteur (CM) et la fréquence dominante du signal du deuxième axe de mesure, est sensiblement égal à deux.detection means (MD) of the gait 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 Euclidean norm of the vector of measurements transmitted by said sensor (CM) and the dominant frequency of the signal of the second measurement axis, is substantially equal to two. 2. Système selon la revendication 1 , dans lequel ladite fenêtre temporelle est une fenêtre glissante.The system of claim 1, wherein said time window is a sliding window. 3. Système selon la revendication 1 ou 2, dans lequel, ledit capteur de mouvement (CM) étant triaxial, le premier axe de mesure dudit capteur (CM) coïncide avec l'axe antéro-postérieur (AP) dudit corps, le deuxième axe de mesure dudit capteur (CM) coïncide avec l'axe médio-latéral (ML) dudit corps, et le troisième axe de mesure dudit capteur (CM) coïncide avec l'axe vertical dudit corps, lesdits moyens de détection (MD) sont adaptés pour détecter un rapport sensiblement égal à deux, entre la fréquence dominante du signal du premier axe de mesure et la fréquence dominante du deuxième axe de mesure, ou entre la fréquence dominante du signal du troisième axe de mesure et la fréquence dominante du deuxième axe de mesure, ou entre la fréquence dominante d'une norme euclidienne du vecteur de mesures transmis par ledit capteur et la fréquence dominante du signal du deuxième axe de mesure.3. System according to claim 1 or 2, wherein, said motion sensor (CM) being triaxial, the first measurement axis of said sensor (CM) coincides with the anteroposterior axis (AP) of said body, the second axis measuring said sensor (CM) coincides with the mediolateral axis (ML) of said body, and the third measurement axis of said sensor (CM) coincides with the vertical axis of said body, said detection means (MD) are adapted to detect 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 Euclidean norm of the measurement vector transmitted by said sensor and the dominant frequency of the signal of the second measurement axis. 4. Système selon l'une des revendications précédentes, comprenant, en outre, des filtres passe-haut (FPH).4. System according to one of the preceding claims, further comprising high-pass filters (FPH). 5. Système selon l'une des revendications précédentes, comprenant, en outre, des filtres passe-bande (FPB).5. System according to one of the preceding claims, further comprising bandpass filters (FPB). 6. Système selon l'une des revendications précédentes, dans lequel lesdits moyens d'analyse (MA) sont internes ou externes audit boîtier (BT), et dans lequel ledit capteur de mouvement (CM) comprend des moyens de transmission (MTR) avec ou sans fil pour transmettre ses mesures auxdits moyens d'analyse (MA).6. System according to one of the preceding claims, wherein said analysis means (MA) are internal or external to said housing (BT), and wherein said motion sensor (CM) comprises transmission means (MTR) with or wirelessly to transmit its measurements to said analysis means (MA). 7. Système selon l'une des revendications précédentes, dans lequel ledit capteur de mouvement (CM) est un accéléromètre biaxial ou triaxial, ou un magnétomètre biaxial ou triaxial, ou un gyromètre biaxial ou triaxial.7. System according to one of the preceding claims, wherein said motion sensor (CM) is a biaxial or triaxial accelerometer, or a biaxial or triaxial magnetometer, or a biaxial or triaxial gyro. 8. Système selon l'une des revendications précédentes, dans lequel la fenêtre glissante est de cinq secondes, avec un recouvrement partiel de quatre secondes entre deux fenêtres consécutives décalées d'une seconde.8. System according to one of the preceding claims, wherein the sliding window is five seconds, with a partial overlap of four seconds between two consecutive windows shifted by one second. 9. Système selon l'une des revendications précédentes, dans lequel lesdits moyens de recherche d'une fréquence dominante (MRFD) pour les signaux transmis par le capteur de mouvement (CM) sont adaptés pour effectuer la recherche de fréquence dominante par analyse spectrale de type spectrogramme. 9. System according to one of the preceding claims, wherein said means for seeking a dominant frequency (MRFD) for the signals transmitted by the motion sensor (CM) are adapted to perform the dominant frequency search by spectral analysis of spectrogram type. 10. Système selon l'une des revendications précédentes, dans lequel lesdits moyens de recherche d'une fréquence dominante (MRFD) sont adaptés pour limiter la recherche d'une fréquence dominante selon le deuxième axe vMι_ à des fréquences comprises entre 0,25 Hz et 1 Hz.10. System according to one of the preceding claims, wherein said means for seeking a dominant frequency (MRFD) are adapted to limit the search for a dominant frequency along the second axis v M ι_ at frequencies between 0, 25 Hz and 1 Hz. 1 1. Système selon l'une des revendications précédentes, dans lequel lesdits moyens de recherche d'une fréquence dominante (MRFD) sont adaptés pour limiter la recherche d'une fréquence dominante selon le premier axe, lorsque celui-ci coïncide avec l'axe antéro-postéheur, à des fréquences comprises entre la fréquence dominante selon le deuxième axe vMι_ Hz augmentée de 0.2 Hz et 3 Hz.1. A system according to one of the preceding claims, wherein said means for seeking a dominant frequency (MRFD) are adapted to limit the search for a dominant frequency along the first axis, when it coincides with the anteroposterior axis, at frequencies between the dominant frequency along the second axis v M ι_ Hz increased by 0.2 Hz and 3 Hz. 12. Système selon l'une des revendications précédentes, dans lequel lesdits moyens de recherche d'une fréquence dominante (MRFD) sont adaptés pour limiter la recherche d'une fréquence dominante selon le premier axe, lorsque celui-ci coïncide avec l'axe vertical, à des fréquences comprises entre la fréquence dominante selon le deuxième axe vMι_ Hz augmentée de 0.2 Hz et 3 Hz.12. System according to one of the preceding claims, wherein said means for finding a dominant frequency (MRFD) are adapted to limit the search for a dominant frequency along the first axis, when it coincides with the axis vertical, at frequencies between the dominant frequency along the second axis v M ι_ Hz increased by 0.2 Hz and 3 Hz. 13. Système selon l'une des revendications précédentes, dans lequel lesdits moyens de recherche d'une fréquence dominante (MEFD) sont adaptés pour limiter la recherche d'une fréquence dominante pour la norme euclidienne du vecteur de mesures transmis par ledit capteur de mouvement, à des fréquences comprises entre la fréquence dominante selon le deuxième axe vMι_ Hz augmentée de 0.2 Hz et 3 Hz.13. System according to one of the preceding claims, wherein said means for seeking a dominant frequency (MEFD) are adapted to limit the search for a dominant frequency for the Euclidean norm of the vector of measurements transmitted by said motion sensor. , at frequencies between the dominant frequency along the second axis v M ι_ Hz increased by 0.2 Hz and 3 Hz. 14. Système selon l'une des revendications précédentes, dans lequel lesdits moyens de détection (MD) sont adaptés pour détecter un rapport desdites fréquences sensiblement égal à deux, à une précision près (Δ), lorsqu'en outre les puissances des signaux respectifs sont supérieures à un seuil. 14. System according to one of the preceding claims, wherein said detecting means (MD) are adapted to detect a ratio of said frequencies substantially equal to two, to a precision by (Δ), when in addition the powers of the respective signals are above a threshold. 15. Système selon l'une des revendications précédentes, dans lequel ledit boîtier (BT) est adapté pour être fixé sur le torse ou sur le sacrum de ladite personne.15. System according to one of the preceding claims, wherein said housing (BT) is adapted to be fixed on the torso or on the sacrum of said person. 16. Procédé de détection de marche d'une personne, à partir de mesures effectuées par un capteur de mouvement biaxial ou triaxial, de mouvements selon un premier axe de mesure dudit capteur (CM) coïncidant avec l'axe antéro-postérieur (AP) ou l'axe vertical (VT) du corps de ladite personne et selon un deuxième axe mesure dudit capteur (CM) coïncidant avec l'axe médio-latéral (ML) dudit corps, caractérisé en ce que :16. A method of detecting a person's walking, from measurements made by a biaxial or triaxial motion sensor, of movements along a first measurement axis of said sensor (CM) coinciding with the anteroposterior axis (AP) or the vertical axis (VT) of the body of said person and along a second axis measuring said sensor (CM) coinciding with the medio-lateral axis (ML) of said body, characterized in that: - on traite, sur une fenêtre temporelle, les signaux de mesure délivrés par ledit capteur de mouvement (CM), ledit traitement comprenant une recherche d'une fréquence dominante dans lesdits signaux etthe measurement signals delivered by said motion sensor (CM) are processed, over a time window, said processing comprising a search for a dominant frequency in said signals and - on détecte la marche de ladite personne lorsqu'un rapport entre la fréquence dominante du signal du premier axe de mesure et la fréquence dominante du deuxième axe de mesure, ou entre la fréquence dominante d'une norme euclidienne du vecteur de mesures transmis par ledit capteur et la fréquence dominante du signal du deuxième axe de mesure, est sensiblement égal à deux. the step 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 Euclidean 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.
EP10705367A 2009-02-26 2010-02-25 System and method for detecting the walk of a person Ceased EP2400889A1 (en)

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FR0951212A FR2942388B1 (en) 2009-02-26 2009-02-26 SYSTEM AND METHOD FOR DETECTING THE MARKET OF A PERSON
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