Fall detection device

Abstract

In a fall detection device, when a first composite vector value of a first acceleration component obtained from a three-axial acceleration sensor is greater than a rotating fall determining value, or smaller than a free fall determining value, a possibility of a fall is determined. When a second composite vector value of a second acceleration component obtained after a determining time interval is greater than the rotating fall determining value, and an angular difference of each testing surface is greater than an angular difference determining value, it is determined to be in the middle of a fall. Further, when a third composite vector value of a third acceleration component obtained one more time is smaller than the free fall determining value, it is determined to be in the middle of a fall.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a fall detection device according to an embodiment of the present invention;

FIG. 2 is a block diagram showing a control unit of the fall detection device according to the embodiment of the present invention;

FIG. 3 is a block diagram showing a storage unit of the fall detection device according to the embodiment of the present invention;

FIG. 4 is a flow chart showing a process of detecting a fall according to the embodiment of the present invention;

FIG. 5 is a graph showing an example of an acceleration component signal of a three-axial acceleration sensor in an X-axis according to the embodiment of the present invention;

FIG. 6 is a graph showing an example of an acceleration component signal of the three-axial acceleration sensor in a Y-axis according to the embodiment of the present invention;

FIG. 7 is a graph showing an example of an acceleration component signal of the three-axial acceleration sensor in a Z-axis according to the embodiment of the present invention; and

FIG. 8 is a graph showing an example of a composite vector value calculated with the fall detection device according to the embodiment of the present invention.

Claims

1. A fall detection device comprising: a three-axial acceleration sensor for detecting acceleration components in three axes crossing perpendicularly with each other, and for outputting acceleration component signals;a first storage unit for storing a rotating fall determining value to determine a rotating fall upon falling, a determining time interval with which the acceleration component signal is obtained again to determine the rotating fall, and an angular difference determining value upon determining the rotating fall;a first obtaining unit for obtaining a first acceleration component signal in each of the three axes from the three-axial acceleration sensor;a first calculating unit for combining the first acceleration component signal in each of the three axes to calculate a first composite vector value;a first reading unit for reading the rotating fall determining value from the first storage unit;a first comparing unit for comparing the rotating fall determining value with the first composite vector value;a second reading unit for reading the determining time interval from the first storage unit when the first composite vector value is grater than the rotating fall determining value;a second obtaining unit for obtaining a second acceleration component signal in each of the three axes from the three-axial acceleration sensor after the determining time interval;a second calculating unit for combining the second acceleration component signal in each of the three axes to calculate a second composite vector value;a second comparing unit for comparing the rotating fall determining value with the second composite vector value;a third calculating unit for calculating an angular difference between a first angle of each of testing surfaces calculated from the first acceleration component signal in each of the three axes and a second angle of each of the testing surfaces calculated from the second acceleration component signal in each of the three axes when the second composite vector value is greater than the rotating fall determining value;a third reading unit for reading the angular difference determining value from the first storage unit;a third comparing unit for comparing the angular difference determining value with the angular difference of each of the testing surfaces; anda first determining unit for determining the rotating fall when at least one of the angular differences of the testing surfaces is greater than the angular difference determining value.

2. The fall detection device according to claim 1, further comprising: a second storage unit for storing a free fall determining value to determine a free fall upon falling,a fourth reading unit for reading the free fall determining value from the second storage unit;a fourth comparing unit for comparing the free fall determining value with the first composite vector value;a fifth reading unit for reading the determining time interval from the first storage unit when the first composite vector value is smaller than the free fall determining value;a third obtaining unit for obtaining a third acceleration component signal in each of the three axes from the three-axial acceleration sensor after the determining time interval;a fourth calculating unit for combining the third acceleration component signal in each of the three axes to calculate a third composite vector value;a fourth comparing unit for comparing the free fall determining value with the third composite vector value; anda second determining unit for determining the free fall when the third composite vector value is smaller than the free fall determining value.

3. The fall detection device according to claim 1, wherein said determining time interval is set to a sampling time for watching one of the rotating fall and the free fall.

4. A method of detecting a fall, comprising the steps of: detecting acceleration components in three axes crossing perpendicularly with each other with a three-axial acceleration sensor;outputting acceleration component signals;storing in a first storage unit a rotating fall determining value to determine a rotating fall upon falling, a determining time interval with which the acceleration component signal is obtained again to determine the rotating fall, and an angular difference determining value upon determining the rotating fall;obtaining a first acceleration component signal in each of the three axes from the three-axial acceleration sensor;combining the first acceleration component signal in each of the three axes to calculate a first composite vector value;reading the rotating fall determining value from the first storage unit;comparing the rotating fall determining value with the first composite vector value;reading the determining time interval from the first storage unit when the first composite vector value is grater than the rotating fall determining value;obtaining a second acceleration component signal in each of the three axes from the three-axial acceleration sensor after the determining time interval;combining the second acceleration component signal in each of the three axes to calculate a second composite vector value;comparing the rotating fall determining value with the second composite vector value;calculating an angular difference between a first angle of each of testing surfaces calculated from the first acceleration component signal in each of the three axes and a second angle of each of the testing surfaces calculated from the second acceleration component signal in each of the three axes when the second composite vector value is greater than the rotating fall determining value;reading the angular difference determining value from the first storage unit;comparing the angular difference determining value with the angular difference of each of the testing surfaces; anddetermining the rotating fall when at least one of the angular differences of the testing surfaces is greater than the angular difference determining value.

5. The method of detecting a fall according to claim 4, further comprising the steps of: storing a free fall determining value in a second storage unit to determine a free fall upon falling;reading the free fall determining value from the second storage unit;comparing the free fall determining value with the first composite vector value;reading the determining time interval from the first storage unit when the first composite vector value is smaller than the free fall determining value;obtaining a third acceleration component signal in each of the three axes from the three-axial acceleration sensor after the determining time interval;combining the third acceleration component signal in each of the three axes to calculate a third composite vector value;comparing the free fall determining value with the third composite vector value; anddetermining the free fall when the third composite vector value is smaller than the free fall determining value.

6. The method of detecting a fall according to claim 4, wherein said determining time interval is set to a sampling time for watching one of the rotating fall and the free fall.