A passively self-tuning nonlinear energy harvester in rotational motion: theoretical and experimental investigation

Recently, various energy harvesters have been investigated for efficiently harvesting energy in rotational motion. However, some challenging issues are still existing in current harvesters, such as narrow operating bandwidth, low-efficiency energy harvesting performance, and so on. To solve these issues, this paper proposes a self-tuning nonlinear piezoelectric energy harvester (PEH) in rotational motion. The corresponding distributed-parameter theoretical model is derived to describe the dynamic response characteristics and predict the energy harvesting performance. Based on this, the principle of a passively self-tuning harvester, which is realized via the centrifugal force acting on the tip mass of the harvester, is theoretically analyzed. Furthermore, experiments are conducted to validate the performance of different nonlinear PEHs under various constant rotational speeds. The experimental results demonstrate that the tri-stable PEH can obtain better energy harvesting performance than the bi-stable one in the low rotational speed range (60-300 rpm). In the high rotational speed range (more than 440 rpm), the bi-stable and tri-stable PEHs achieve the passive self-tuning effect in the ranges of 440-720 rpm and 990-1300 rpm, respectively. These different self-tuning rotational speed ranges are caused by the different rotational radiuses in rotational motion. Overall, this paper provides a theoretical framework to achieve a self-tuning energy harvester in rotational motion.