Lower Limb-Driven Energy Harvester: Modeling, Design, and Performance Evaluation

Abstract

Biomechanical energy harvesters (BMEHs) have shown that useable amounts of electricity can be generated from daily movement. Where access to an electrical power grid is limited, BMEHs are a viable alternative to accommodate energy requirements for portable electronics. In this paper, we present the detailed design and dynamic model of a lower limb-driven energy harvester that predicts the device output and the load on the user. Comparing with existing harvester models, the novelty of the proposed model is that it incorporates the energy required for useful electricity generation, stored inertial energy, and both mechanical and electrical losses within the device. The model is validated with the lower limb-driven energy harvester in 12 unique configurations with a combination of four different motor and three different electrical resistance combinations (3.5 Ω, 7 Ω, and 12 Ω). A case study shows that the device can generate between 3.6 and 15.5 W with an efficiency between 39.8% and 72.5%. The model was able to predict the harvester output peak voltage within 5.6 ± 3.2% error and the peak force it exerts on the user within 9.9 ± 3.4% error over a range of parameter values. The model will help to identify configurations to achieve a high harvester efficiency and provide a better understanding of how parameters affect both the timing and magnitude of the load felt by the user.

A transition point: Assistance magnitude is a critical parameter when providing assistance during walking with an energy-removing exoskeleton or biomechanical energy harvester

“…Additionally, this decoupling enables the device to apply mechanical load only during the swing period [ 8 ]. The electromagnetic force produced by the generator and applied to the user by the input cables is controlled using a custom-designed linear regulator and an Arduino-based control system [ 30 , 31 ]. This control system uses a hybrid approach consisting of an open-loop control scheme for predicting and applying the desired load and a closed-loop feedback control scheme for high-level regulation of the applied angular impulse.…”

Biomechanical Regenerative Braking Energy Harvester: A Systematic Analysis

“…In most previous studies using one-way clutches, it was not possible to determine whether these characteristics occurred because the velocity was not measured. Only one study analyzed the dynamic characteristics [ 32 ]; however, in this case, delay and overrunning were not observed. It could be attributed to the unique characteristics of each commercial one-way clutch and differences in the BRBEH design parameters.…”

“…In [ 31 ], a high-efficiency BRBEH was designed by predicting the device efficiency and electrical power according to the gear ratio. Another study compared the device efficiency of different commercial generators and electrical loads [ 32 ]. In other studies, the knee joint torque was predicted according to the change in the spring or damping constant of the proposed mechanism [ 41 , 42 ].…”

Biomechanical knee energy harvester: Design optimization and testing

“…However, they found that dynamic effects can account for as much as half of the resistance torque applied by the device, which means that the device parameters chosen by their optimization might not have been optimal. Martin et al (2016) proposed a model that included dynamic effects for a lower limb-driven energy harvester. However, they did not suggest a framework for optimizing the design parameters of the harvester.…”