Foot angle calculation

1. A system comprising:

a sensor installed in a shoe at a position at which the sensor faces a back side of an arch of a foot inserted in the shoe, the sensor configured to detect an angular velocity and an acceleration of the foot;

at least one memory storing instructions; and

at least one processor connected to the at least one memory and configured to execute the instructions to:

receive, from the sensor, sensor data including an angular velocity vector and an acceleration vector of the foot;

calculate a velocity vector of the foot portion by using the acceleration vector;

calculate a posture angle by using the angular velocity vector of the foot portion;

calculate a foot angle formed by the velocity vector of the foot portion and a center line of the foot by using the velocity vector and the posture angle; and

output information regarding the calculated foot angle.

2. The system according to claim 1 ,

the at least one processor is configured to execute the instructions to

calculate the velocity vector by time-integrating the acceleration vector.

3. The system according to claim 1 , wherein

the at least one processor is configured to execute the instructions to

calculate the foot angle by using the velocity vector averaged in a swing phase.

4. The system according to claim 3 , wherein

the at least one processor is configured to execute the instructions to

calculate the foot angle by using the velocity vector weighted in a mid-swing period included in the swing phase.

5. The system according to claim 1 , wherein

the at least one processor is configured to execute the instructions to

output the information regarding the calculated foot angle to a display device.

6. The system according to claim 1 , wherein

the at least one processor is configured to execute the instructions to

output the information regarding the calculated foot angle to a notification device.

7. A gait measurement method performed by a system and comprising:

detecting, by a sensor of the system installed in a shoe at a position at which the sensor faces a back side of an arch of a foot inserted in the shoe, an angular velocity and an acceleration of the foot;

receiving, by at least one processor of the system from the sensor, sensor data including an angular velocity vector and an acceleration vector of the foot;

calculating, by the at least one processor, a velocity vector of the foot portion by using the acceleration vector;

calculating, by the at least one processor, a posture angle by using the angular velocity vector of the foot portion;

calculating, by the at least one processor, a foot angle formed by the velocity vector of the foot portion and a center line of the foot by using the velocity vector and the posture angle; and

outputting, by the at least one processor, information regarding the calculated foot angle.

8. A non-transitory program recording medium storing a program executable by at least one processor of a system comprising a sensor installed in a shoe at a position at which the sensor faces a back side of an arch of a foot inserted in the shoe, the sensor configured to detect an angular velocity and an acceleration of the foot, the program executable by the at least one processor to perform processing comprising:

receiving, from the sensor, sensor data including an angular velocity vector and an acceleration vector of the foot;

calculating a velocity vector of the foot portion by using the acceleration vector;

calculating a posture angle by using the angular velocity vector of the foot portion;

calculating a foot angle formed by the velocity vector of the foot portion and a center line of the foot by using the velocity vector and the posture angle; and

outputting information regarding the calculated foot angle.