Asymmetric plucking bistable energy harvester: Modeling and experimental validation

Abstract

Incorporation of plucking up-conversion and bistable energy harvesting techniques can be solutions to enhance energy harvested from large-amplitude impulsive-type events. This work proposes an asymmetric plucking-based bistable energy harvester with rotary structure and plectrum, to convert the impulsive excitation to plucking force that helps the harvester jump into the high-energy orbit. The bistable configuration is set to be asymmetric in order to achieve repeatable mechanical plucking condition, ensuring the feasibility and stability of the proposed system. Hertzian contact theory is employed to relate different oscillation modes with dynamic plucking force under variations of plucking velocity and overlap length. By considering the deformation and rotational angle of beam tip during vibration, geometrically dipole-dipole model is adopted to calculate the asymmetric magnetic force and study potential well in contrast to the symmetric configuration. With the fact that linear damping model often misses its physical essentials in bistable systems, nonlinear damping model is employed to account for the energy dissipation process. Experiments show qualitative agreement with simulation results in terms of system responses and power output under different velocities, overlap lengths and load resistances. Compared with plucking energy harvester without bi-stability, the proposed system is able to improve the power output by up to 22.9% for single plucking cycle and 29.8% for periodic plucking. Parametric studies based on nondimensionalization are further conducted to investigate the mechanisms that control the energy characteristics of the system, thus providing a foundation to develop an optimal plucking bistable energy harvester.