Rotational energy harvesting has received massive attractions due to the abundance and availability of rotational motions in ambient environments. This paper considers a rotational impact energy harvester by utilizing the static instability of a centrifugal softening beam. During the rotation, two rigid piezoelectric beams are impacted by the centrifugal softening driving beam to generate electric energy. When the rotational frequency is increased, with the centrifugal effect, the amplified relative motion between the driving and generating beams significantly contributes to the increase of the impact force and in turn the output power. The theoretical model is developed and used for numerical simulation. It is shown that the output voltage can be significantly improved with the centrifugal softening effect. Furthermore, the impact force is demonstrated to prevent the driving beam from continuously deflecting and suffering the mechanical failure.
Recent researchers have focused on scavenging energy from ambient vibrations or movements by using piezoelectric energy harvesters. Rotary movements are regarded as potential energy resources as they can be utilized in windmills or turnstile gates in stations. This study aims to study the vibrational interference that could occur in the typical rotational plucking energy harvester with circularly distributed plectra on the outer ring plucking on the circular array of multiple piezoelectric cantilevers on the inner hub. In this structure, the plucking frequency will be increased to times of the input rotational frequency since multiple plectra will participate in the deflection of each piezoelectric cantilever for one rotational cycle. A model is established based on the Hamilton’s principle for the basic electromechanical part and the Hertzian contact theory for the solution of plucking force. Based on the developed model, the simulation results of the system responses of the rotational plucking energy harvester (RPEH) in a wide rotational frequency range reveal that the system may be suppressed by the vibrational interference such that the energy output is restricted as the rotational frequency is increased. The induced plucking force has also been plotted to reproduce the dynamic contact process and investigate the variation of the force amplitude with rotational frequency. An overall investigation of the energy harvesting performance also indicates the influence of the vibrational interference on the RPEH structure.
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