Abstract
Wearable ground reaction force (GRF) measurement systems make it possible to measure the GRF in any environment, unlike a commercial force plate. When performing kinetic analysis with the GRF, measurement of multiaxial GRF is important for evaluating forward and lateral motion during natural gait. In this paper, we propose a bendable GRF measurement system that can measure biaxial (vertical and anterior-posterior) GRF without interrupting the natural gait. Eight custom small biaxial force sensors based on an optical sensing mechanism were installed in the proposed system. The interference between two axes on the custom sensor was minimized by the independent application of a cantilever structure for the two axes, and the hysteresis and repeatability of the custom sensor were investigated. After developing the system by the installation of force sensors, we found that the degree of flexibility of the developed system was comparable to that of regular shoes by investigating the forefoot bending stiffness. Finally, we compared vertical GRF (vGRF) and anterior-posterior GRF (apGRF) measured from the developed system and force plate at the same time when the six subjects walked, ran, and jumped on the force plate to evaluate the performance of the GRF measurement system.
Highlights
The measurement of ground reaction force (GRF) is a representative kinetic analysis method in biomechanics, and the GRF measurement has been widely used in the diagnosis of abnormal gaits, control of exoskeleton, and evaluation of athletics’ performance [1,2,3,4]
The small force sensor that can measure the biaxial forces with a high capacity and high repeatability cannot be constructed
The GRF concentrated point was between two sensors at the heel, the signal of each sensor occurs simultaneously and the GRF at the heel is the sum of the force measured by each sensor
Summary
The measurement of ground reaction force (GRF) is a representative kinetic analysis method in biomechanics, and the GRF measurement has been widely used in the diagnosis of abnormal gaits, control of exoskeleton, and evaluation of athletics’ performance [1,2,3,4]. A stationary force plate has been primarily used to measure the GRF [5,6], but this method can be used only in a controlled environment, and the awareness of stepping on the correct position of the force plate can hinder one’s natural gait [7,8]. To overcome the drawbacks of the force plate, many efforts have been focused on the development of wearable GRF measurement systems. A wearable system can be used in various environments while measuring the GRF during natural walking and can be used to analyze various gait parameters, such as gait speed and stride length, among others, without distortion due to hindering the natural gait. Wearable GRF measurement systems can be categorized as either the insole type or outsole type.
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