Wearable sensor system including optical 3-axis GRF sensor for joint torque estimation in real-time gait analysis

In this paper, we developed wearable sensor system for joint torque estimation in gait analysis. In particular, the proposed wearable sensor system contains a novel wearable GRF (ground reaction force) sensor using force measurement units based on the light-intensity modulation technique. Thanks to its structure and optical properties, it has considerable advantages such as clean signals, compactness, and low-mass. The proposed GRF sensor can detect 3-axial complete GRFs. Also, it is light-weight (mass: 310g) and compact (thickness: 10mm) such that it does not impede a human's natural motion during daily-life-activities. In addition, wearable motion sensors has been developed using commercial IMUs. The body-worn IMUs are the alternative solution for camera-based motion capture system to overcome spatial limitation. The joint torques of ankle, knee, and hip were calculated by utilizing the proposed wearable sensor system in real-time. The value of torques were validated by experiment, and compared to the reference values from the conventional sensor system; stationary force plate and camera-based motion sensor. The results were highly correlated with those of the reference system. It is expected that the proposed wearable sensor system may satisfy the increasing demand for a cheap and reliable motion sensor without space-restriction.