Flexible Insole Ground Reaction Force Measurement Shoes for Jumping and Running

Abstract

There are only a few insole ground reaction force (GRF) measurement systems for running and jumping because the capacity and durability of the system were not guaranteed to measure the heavy load on the foot. We propose insole-type measurement system that can measure up to 900N to assure the capacity of GRF during running and jumping. The proposed system was implemented using a sensor-embedded flexible shoe including four custom optoelectronic based force sensors with high reliability. In order to evaluate the performance of the proposed sensor, static loading and unloading tests were performed to compare the hysteresis with the force sensitive resistors (FSR) which are widely used in insole-type system. During test, FSR and the proposed force sensor were loaded to the reference force sensor simultaneously; the hysteresis error of the proposed system (4.8%) was better than that of FSR (23.54%). By utilizing these custom force sensors, the proposed system was manufactured and evaluated for walking, running at 8km/h and withstanding high jump experiments with the 6-axis force plate based on NRMSE (Normalized Root Mean Square Error). The results were 14.68± 4.75% for long period walking, 10.9± 6.5% for running, and 14.72± 4.44% for jumping. From these results, the proposed system helps to measure GRFs in real-time for various human movement.