Wireless Ground Reaction Force Sensing System Using a Mechanically Decoupled Two-Dimensional Force Sensor

摘要

We present the design process of a mechanically decoupled two-dimensional force sensor (M2D) for the implementation of a wearable ground reaction force (GRF) sensing system. The proposed sensor is capable of sensing up to 1000 and $ pm ext{300 N}$ in the vertical GRF (vGRF) direction and the anterior-posterior GRF (apGRF) direction, respectively, with accuracies of $ext{2.81} pm ext{0.29}%$ and $ext{1.67} pm ext{0.15}%$, respectively. With only two reflective optical sensors for each M2D, one for each axis, the mechanical structure of the M2D allows two-dimensional forces to be measured with an axial interference of approximately 1.37% and 2.39% and a repeatability of 0.95% and 1.35% for vGRFs and apGRFs, respectively. A wireless, wearable GRF sensing system was implemented using two M2Ds attached to the outsole of a shoe: one at the heel and the other at the forefoot. The normalized root mean square error value between a conventional stationary force plate and the proposed system for 30 consecutive steps of five subjects was approximately $ext{4.93} pm ext{2.56}% $ and $ext{4.22} pm ext{2.12}% $ for the vGRF and the apGRF, respectively.