Procedure and system for detecting a person's fall

• US 7,423,537 B2
• Filed: 06/05/2006
• Issued: 09/09/2008
• Est. Priority Date: 06/07/2005
• Status: Active Grant

• Current Assignee: Commissariat a L'Energie Atomique (AES Corporation)
• Original Assignee: Commissariat a L'Energie Atomique (AES Corporation)
• Inventors: Bonnet, Stephane, Guillemaud, Regis
• Primary Examiner(s): La; Anh V
• Application Number:
  US11/446,356
• Publication Number:
  US 20060279426A1
• Time in Patent Office: 827 Days
• Field of Search: 340/573.1, 340/573.7, 340/689, 340/506, 340/539.1, 340/576, 340/686.1, 128/904, 128/903, 600/300, 600/301, 600/483, 600/503
• US Class Current: 340/573.1
• CPC Class Codes: A61B 2562/0219 Inertial sensors, e.g. accelerometers, gyroscopes, tilt switches
• CPC Class Codes: A61B 5/1117 Fall detection
• CPC Class Codes: G06F 2218/00 Aspects of pattern recognition specially adapted for signal processing
• CPC Class Codes: G06V 40/23 Recognition of whole body movements, e.g. for sport training

Abstract

A person under supervision wears a sensor consisting of at least one accelerometer (31) and a magnetometer (41), oriented in his vertical direction. A fall event is picked up when a significant and rapid oscillation of the acceleration signal coincides with a shift in the ambient magnetic field between two levels (between t=4000 and t=5000). Additional criteria that may also make use of the magnetometer enable the diagnosis to be made, and it is easier and safer to establish this than with accelerometers alone.

Claims

1. A process for detecting a fall of a person, comprising the following steps:

placing a sensor on the person, said sensor comprising at least one accelerometer and at least one magnetometer;

monitoring an acceleration signal and an ambient magnetic field signal provided by the sensor;

analyzing changes in said acceleration signal and said ambient magnetic field signal;

indicating a fall when a plurality of criteria have been met, the criteria including;

a) identifying the presence of a first period of instability in a vertical component of the acceleration signal, followed by a second period of instability in said vertical component of the acceleration signal;

said vertical component being considered in a height direction of the person, and

b) discriminating between a fall and other events by analyzing a portion of the ambient magnetic field signal during said first period and said second period.

2. The process according to claim 1, wherein the portion of the ambient magnetic field signal includes a component of the ambient magnetic field along said height direction.

3. The process according to claim 2, wherein said discriminating includes indicating that a fall did not happen when said component of the ambient magnetic field along said height direction does not vary above a threshold in said portion of the ambient magnetic field signal.

4. The process according to claim 1, wherein the criteria further include:

c) detecting a recumbent position of the person if the vertical component of the acceleration signal is near zero during the second period.

5. The process according to claim 1, wherein said discriminating is performed by comparing said portion of the ambient magnetic field signal with equivalent portions of signals recorded previously and respectively corresponding to normal events.

6. The process according to claim 5, wherein said comparing is performed for a part of the portion of the ambient magnetic field signal, said part corresponding to either the first period of instability or the second period of stability.

7. The process according to claim 6, wherein said analyzing of the ambient magnetic field signal includes determining an azimuth of the person.

8. The process according to claim 7, wherein one of the normal events includes laying on a bed and said comparing includes comparing the azimuth of the person during the second period and an azimuth of the bed.

9. The process according to claim 1, wherein said indicating comprises indicating a fall after a threshold is crossed by a weighted numerical combination of the criteria.

10. The process according to claim 1, further comprising converting raw measurements of the sensor to express components of signal axes associated with the person and consisting of a vertical axis, an antero-posterior axis and a medio-lateral axis.

11. The process according to claim 1, wherein said sensor includes at least three accelerometers that measure acceleration in three orthogonal axes and at least three magnetometers that measure the ambient magnetic field in the three orthogonal axes.

12. The process according to claim 11, wherein said sensor has a range of measurement of about +/−

5 g for the accelerometers and about 50 micro-Telsa for the magnetometers.

13. The process according to claim 1, wherein said monitoring is performed continuously.

14. The process according to claim 1, wherein said discriminating is performed by comparing said ambient magnetic field signal before and after at least one of said first and second periods of instability.

15. The process according to claim 14, wherein said discriminating is performed by identifying said fall when said ambient magnetic field signal shows two plateaus at different levels before and after said at least one of said first and second periods of instability.

16. The process according to claim 14, wherein said discriminating is performed by identifying said fall when said vertical component of said acceleration signal is effectively zero after said at least one of said first and second periods of instability.

17. The process according to claim 1, wherein said first and second periods of instability are defined by oscillations in said acceleration signal and are separated by a period of stability during which said acceleration signal is relatively constant.

18. The process according to claim 1, wherein said step of indicating comprises transmitting a signal to a display device, wherein said signal signals that said fall occurred, and said display device produces an alarm indicating that said fall occurred.