Biomechanical Energy Harvester with Continuously Variable Transmission: Prototyping and Preliminary Evaluation

In this paper, we introduce a new concept of biomechanical energy harvester that can harvest electrical energies from wearers performing various activities of daily living such as walking and running. Due to a trade-off between the amount of electric-power generation and the degree of keeping user's natural movements, the transmission ratio of the wearer's angular velocity to that of the electromagnetic generator needs to be adjusted for several factors as physical properties of the wearer, gait patterns, and environmental conditions. To make it possible, our harvester is equipped with a Continuously Variable Transmission (CVT) system. We developed a prototype of our harvester attached to a knee joint, and conducted preliminary experimental evaluations with human subjects in walking and running using the prototype. Experimental results suggest that changing the transmission ratio according to individual and gait speed is beneficial to maximize the capacity of harvested electric energy from the wearer without suppressing natural movements, thereby proving our concept.