A Soft Capacitive Wearable Sensing System for Lower-Limb Motion Monitoring

Abstract

Human limb motion monitoring has been a challenging task for robotic applications in unstructured environments, because traditional sensing methods are limited in conforming to compliant human bodies and adapting to unpredictable external disturbances. Motivated by the need to capture rotation angles of lower-limb joints in real time, this paper proposes a soft wearable sensing system based on a network of soft capacitive sensors that can be stretched with joint bending. The capacitance of the sensing module changes with the sensor deformations thus its deviated value from the initial installation state is closely related to the joint rotation angle. The sensor fabrication is developed with shape deposition molding, and the sensing electronics are designed to improve signal transmission and sensing robustness. The sensing system is calibrated with machine vision and its performance is evaluated in walking tests with different speeds. An illustrative example is presented to verify the proposed method capable to monitor human lower-limb motions in practice.