Modeling and experimental verification of a pendulum-based low-frequency vibration energy harvester

The pendulum-plucked rotational energy harvester (PP-REH) can realize efficient exploitation of low-frequency vibrations by transforming them to one-way rapid spin of a rotor via a pendulum and a plectrum. A route is conceived in this study to construct the plectrum that can achieve sufficiently large forward stiffness for spinning the rotor and a very small backward stiffness for making the frictional resistance as low as possible. An electromechanical coupling model of the PP-REH is also proposed and verified by experiment to describe the PP-REH dynamic responses. The simulations reveal that the shift of the optimal frequency of the PP-REH with the applied vibration magnitude is due to the large-angle swing of the pendulum. The change of the optimal load resistance is caused by the fact that the power generation unit of the PP-REH is excited indirectly by the exerted vibration, making the electrical damping effect on the PP-REH responses discernible. The proposed electromechanical model can not only predict the PP-REH output performance but also reveal the intriguing phenomena found in the PP-REH dynamics. The model thus can facilitate the design of efficient PP-REHs to achieve high electric outputs from pervasive low-frequency vibrations.