Development of instrumented outsole for high resolution ground reaction force sensing

This paper proposes a compact ground reaction force (GRF) sensing system equipped with high resolution in-house force sensors. The use of optical based sensor which does not require additional signal amplifiers makes the system compact. The system was designed as outsole type platform separated into three parts (toe, ball, and heel part) to reduce interference and adjust to the foot curvature. Seven in-house force sensors were used; two sensors (x and z direction) at the toe, three sensors (two z and one y direction) at the ball, and two sensors (y and z directions) at the heel. The measured forces were transmitted to host computer by an embedded module nearby the platform. The calibration of the proposed system was undertaken using a commercial force sensor. To validate the performance of the proposed system, walking experiment was carried out and the results of the proposed system were compared to those of the force plate.