Leaf-Inspired FSR Array and Insole-Type Sensor Module for Mobile Three-Dimensional Ground Reaction Force Estimation

This paper presents an insole-type sensor module with a novel leaf-inspired force-sensitive resistor (FSR) array for accurate three-dimensional ground reaction force (GRF) estimation during human’s various motions. Joint torque analysis, essential for numerous applications in biomechanics and wearable robotics, necessitates the measurement of three-dimensional GRF vector information, traditionally achieved in indoor environments using costly force plates. To overcome these limitations, this study proposes an alternative method by incorporating FSRs on three inclined planes within the insole. A vector scaling process transforms the force values from the FSRs into the three-dimensional force vector, enabling continuous and user-independent estimation of GRF. The sensor module is integrated with machine learning, demonstrating its accuracy and usability in various motion scenarios. The results confirm the effectiveness of the leaf-inspired FSR array, giving the possibilities for portable and cost-effective motion analysis systems.