Circuit Designing for Charging Energy Storage Batteries with a Knee-joint Biomechanical Energy Harvester Aiming at the Optimal Total-Cost-of-Harvesting

In the context of long-distance trekking, providing stable and continuous power for mobile electronic devices is a challenging issue. In recent years, scholars have designed knee-joint biomechanical energy harvesters to capture the human body’s dissipated kinetic energy and convert it into electricity to solve this problem. In this paper, we propose a circuit for charging the energy storage battery using a harvester and a design method for the harvester’s transient element parameters to achieve optimal TCOH, which is a performance indicator that describes the total additional metabolic energy consumed by the harvester when generating a unit of electric energy. By modeling the dynamics of lower limbs, human-harvester interaction, and transient circuit, a calculation method was derived for calculating TCOH and power generation when using this circuit on the harvester. The feasibility of the design method was verified by creating a prototype and conducting experiments with human subjects. The results show that at a walking speed of 4.2 km/h, the prototype can generate 2.18 W of electric energy, while the TCOH value is only 2.96, which is lower than that of other harvesters.