Device for analyzing gait

• US 8,529,475 B2
• Filed: 02/03/2009
• Issued: 09/10/2013
• Est. Priority Date: 02/04/2008
• Status: Active Grant

• Current Assignee: Commissariat a L'Energie Atomique (AES Corporation)
• Original Assignee: Commissariat a L'Energie Atomique (AES Corporation)
• Inventors: Bonnet, Stephane
• Primary Examiner(s): Sample, David
• Assistant Examiner(s): KHAN, TAHSEEN
• Application Number:
  US12/364,752
• Publication Number:
  US 20090198155A1
• Time in Patent Office: 1,680 Days
• Field of Search: 428/212, 600/595, 324/261
• US Class Current: 600/595
• CPC Class Codes: A61B 5/1038 Measuring plantar pressure during gait
• CPC Class Codes: A61B 5/1127 using markers
• CPC Class Codes: A61B 5/6828 Leg

Abstract

A method and device for analyzing a gait of a person includes a magnetometer for fastening to a tibial segment of the person, in order to generate a signal representative of at least one projection onto a sagittal plane of an ambient magnetic field in which the magnetometer is immersed and a signal processor to identify instants and/or phases that are characteristic of the gait of the person by identifying particular points in the signal generated by the magnetometer as a function of time.

Claims

1. A device for analyzing a gait of a person, the device comprising:

a magnetometer for fastening to a tibial segment of said person, in order to generate a signal representative of at least one projection onto a sagittal plane of an ambient magnetic field in which the magnetometer is immersed; and

signal processor means for identifying instants that are characteristic of the gait of said person solely by identifying particular points in the signal generated by the magnetometer as a function of time,

wherein said instants that are characteristic of the gait of said person comprise at least one selected from a group including a toe-off and a heel-strike instant.

2. A device according to claim 1, wherein said signal processor means is adapted to identify the characteristic instants of the person'"'"'s gait by identifying local extrema in the signal generated by the magnetometer as a function of time for an angle formed by said projection onto the sagittal plane of the ambient magnetic field relative to said tibial segment.

3. A device according to claim 1, wherein said signal processor means is adapted to identify the characteristic instants of the person'"'"'s gait by identifying local extrema in the signal generated by the magnetometer as a function of time for a component that is substantially perpendicular to the person'"'"'s tibial segment of said projection onto the sagittal plane of the ambient magnetic field.

4. A device according to claim 1, wherein said processor means is also adapted to receive as input calibration information indicative of an inclination of said ambient magnetic field relative to a vertical direction of the tibial segment, and to determine an angle between said tibial segment and a vertical axis at said characteristic instants of the person'"'"'s gait based on said calibration information.

5. A device according to claim 1, further comprising a second magnetometer adapted to be fastened to a thigh of the person, said second magnetometer being adapted to generate a second signal representative of at least one projection onto the sagittal plane of the ambient magnetic field in which the second magnetometer is immersed;

wherein said signal processor means is also adapted to determine a flexing angle of a knee of the person from the signal generated by said magnetometers.

6. A device according to claim 1, wherein the signal processor means is a computer.

7. A device according to claim 1, wherein the ambient magnetic field is the Earth'"'"'s magnetic field.

8. A device according to claim 1, wherein said instants that are characteristic of the gait of said person comprise the toe-off instant and the heel-strike instant.

9. A device according to claim 1, wherein said signal processor means is adapted to identify the characteristic instants of the person'"'"'s gait by identifying local extrema in the signal generated by the magnetometer as a function of time for a time derivative of an angle formed, relative to said tibial segment, by said projection onto the sagittal plane of the ambient magnetic field.

10. A device according to claim 9, wherein the local extrema identified by the signal processor means include

a first extreme to identify a mid-swing instant of the gait, the first extreme being greatest amplitude in absolute value of the extrema,

a second extreme to identify a flat foot instant of the gait, the second extreme being a same sign and immediately preceding or following the first extreme of the extrema,

a third extreme to identify the toe-off instant of the gait, the third extreme being a sign opposite to and immediately preceding the first extreme of the extrema, and

a fourth extreme to identify the heel-strike instant of the gait, the fourth extreme being a sign opposite to and immediately following the first extreme of the extrema.

11. A device according to claim 1, wherein said magnetometer is a three-axis magnetometer.

12. A device according to claim 11, wherein said processor means is also adapted to determine a gait heading from a signal representative of at least one medio-lateral component of said ambient magnetic field, the signal representative of at least one medio-lateral component being generated by said magnetometer.

13. A method of analyzing a gait of a person, comprising:

fastening a magnetometer to a tibial segment of the person to generate a signal representative of at least one projection onto a sagittal plane of an ambient magnetic field in which the magnetometer is immersed; and

identifying instants that are characteristic of the gait of said person solely by identifying particular points in the signal generated by the magnetometer as a function of time,

wherein said instants that are characteristic of the gait of said person comprise at least one selected from a group including a toe-off and a heel-strike instant.

14. A method according to claim 13, wherein the identifying includes identifying the characteristic instants of the person'"'"'s gait by identifying local extrema in the signal generated by the magnetometer as a function of time for an angle formed by said projection onto the sagittal plane of the ambient magnetic field relative to said tibial segment.

15. A method according to claim 13, wherein the identifying includes identifying the characteristic instants of the person'"'"'s gait by identifying local extrema in the signal generated by the magnetometer as a function of time for a component that is substantially perpendicular to the person'"'"'s tibial segment of said projection onto the sagittal plane of the ambient magnetic field.

16. A method according to claim 13, wherein the identifying includes determining a gait heading from a signal representative of at least one medio-lateral component of said ambient magnetic field, the signal representative of at least one medio-lateral component being generated by said magnetometer.

17. A method according to claim 13, wherein the identifying includes receiving as input calibration information indicative of an inclination of said ambient magnetic field relative to a vertical direction of the tibial segment, and determining an angle between said tibial segment and a vertical axis at said characteristic instants of the person'"'"'s gait based on said calibration information.

18. A method according to claim 13, wherein said instants that are characteristic of the gait of said person comprise the toe-off instant and the heel-strike instant.

19. A method according to claim 13, wherein the identifying includes identifying the characteristic instants of the person'"'"'s gait by identifying local extrema in the signal generated by the magnetometer as a function of time for a time derivative of an angle formed, relative to said tibial segment, by said projection onto the sagittal plane of the ambient magnetic field.

20. A method according to claim 19, wherein the local extrema identified by the signal processor means include

a first extreme to identify a mid-swing instant of the gait, the first extreme being greatest amplitude in absolute value of the extrema,

a second extreme to identify a flat foot instant of the gait, the second extreme being a same sign and immediately preceding or following the first extreme of the extrema,

a third extreme to identify the toe-off instant of the gait, the third extreme being a sign opposite to and immediately preceding the first extreme of the extrema, and

a fourth extreme to identify the heel-strike instant of the gait, the fourth extreme being a sign opposite to and immediately following the first extreme of the extrema.