Detecting method, detecting device, and detecting system

1. A detecting device for determining whether an attached position of a body motion sensor being attached to a body of a person and configured to detect shifting of the body motion sensor from an initially attached position, the device comprising:

a processor; and

a memory,

the processor configured to obtain a reference-walk-waveform by

detecting a first body motion signal from the body motion sensor while the person walks,

determining a parameter of a walking condition of the person from the first body motion signal and determining from the parameter a stride of the person walking that generates the first body motion signal from the body motion sensor,

determining if the determined stride is to be used in detecting a shift of the body motion sensor from the initially attached position,

if the determined stride is not to be used in detecting the shift of the body motion sensor from the initially attached position,

increasing a first stride presented to the person for obtaining the reference-walk-waveform by a predetermined distance, and

determining whether the increased stride presented to the person is to be used in detecting the shift of the body motion sensor from the initially attached position,

if the determined stride is to be used in detecting the shift of the body motion sensor from the initially attached position,

determining the reference-walk-waveform from the first body motion signal, and

saving the determined reference-walk-waveform in the memory, wherein the saved reference-walk-waveform represents a predetermined stride,

obtaining a second body motion signal from the body motion sensor while the person walks with the predetermined stride, the body motion sensor being attached to the body of the person and configured to detect the body motion of the person,

reading out the obtained reference-walk-waveform from the memory,

comparing the read-out reference-walk-waveform with a waveform of the obtained second body motion signal to determine whether an attached position of the body motion sensor is shifted from the initially attached position, and

outputting a result of the comparing.

2. A method performed by a computer of determining whether an attached position of a body motion sensor being attached to a body of a person and configured to detect shifting of the body motion sensor from an initially attached position, the method comprising:

obtaining a reference-walk-waveform by

detecting a first body motion signal from the body motion sensor while the person walks,

determining a parameter of a walking condition of the person from the first body motion signal and determining from the parameter a stride of the person walking that generates the first body motion signal from the body motion sensor,

determining if the determined stride is to be used in detecting a shift of the body motion sensor from the initially attached position,

if the determined stride is not to be used in detecting the shift of the body motion sensor from the initially attached position,

increasing a first stride presented to the person for obtaining the reference-walk-waveform by a predetermined distance, and

determining whether the increased stride presented to the person is to be used in detecting the shift of the body motion sensor from the initially attached position,

if the determined stride is to be used in detecting the shift of the body motion sensor from the initially attached position,

determining the reference-walk-waveform from the first body motion signal, and

saving the determined reference-walk-waveform in the memory, wherein the saved reference-walk-waveform represents a predetermined stride,

obtaining a second body motion signal from the body motion sensor while the person walks with the predetermined stride;

reading out the obtained reference-walk-waveform from the memory;

comparing the read-out reference-walk-waveform with a waveform of the obtained second body motion signal to determine whether an attached position of the body motion sensor is shifted from the initially attached position; and

outputting a result of the comparing.

3. The method according to claim 2 , the body motion sensor being configured to detect an acceleration of the body of the person and output an acceleration signal, the method further comprising:

calculating the walking condition including at least one of a maximum value of the acceleration, the stride of the person, and a walk cycle of the person based on the acceleration signal obtained from the body motion sensor, and

wherein whether the person is walking with the predetermined stride is determined based on the calculated walking condition.

4. The method according to claim 2 , the body motion sensor being configured to detect an acceleration of the body of the person and output an acceleration signal, the method further comprising:

obtaining a gravity-center signal from a pressure sensor that detects a change in a gravity center of the person while the person walks; and

calculating the walking condition including at least one of a maximum value of the acceleration, the stride of the person, and a walk cycle of the person based on the acceleration signal obtained from the body motion sensor and the gravity-center signal obtained from the pressure sensor, and

wherein whether the person is walking with the predetermined stride is determined based on the calculated walking condition.

5. The method according to claim 3 , wherein at least one of a standard deviation of the calculated maximum value of the acceleration, a standard deviation of the stride of the person, and a standard deviation of the walk cycle of the person is calculated, and it is determined that the person is walking with the predetermined stride when at least one of the calculated standard deviation of the maximum value of the acceleration, the standard deviation of the stride, and the standard deviation of the walk cycle is below a threshold value.

6. The method according to claim 2 , wherein the reference-walk-waveform is generated by averaging a plurality of body motion signals cut out from the first body motion signal at every walk cycle.

7. The method according to claim 2 , wherein the comparing operation determines that the attached position of the body motion sensor is shifted from the initially attached position when at least one of differences, regarding a walk cycle, the stride, and a maximum value, between the reference-walk-waveform and the waveform of the obtained second body motion signal is equal to or higher than a threshold.

8. The method according to claim 2 , wherein the body motion sensor is attached to an ankle of the person.

9. A detecting system comprising:

the body motion sensor; and

the detecting device according to claim 1 .