A Shoe-Embedded RF Sensor for Motion Detection

Inertial Measurement Unit (IMU) based pedestrian navigation systems suffer from long term inaccuracy due to sensor bias drift. Zero velocity update (ZUPT) algorithms can estimate the drift and improve the system accuracy. Accurate zero velocity period detection is critical for the performance of ZUPT algorithms. A low power shoe-embedded RF sensor is proposed to identify zero velocity periods of a foot when a person is walking. This letter reports the hardware system development and the performance characterizations. The results show that the sensor can detect relative position changes with an accuracy of better than 1.3 mm and a velocity as low as 191 μm/s. The developed miniature sensor was embedded into the heel, and zero velocity periods were successfully detected during walking tests.