Increasing the efficiency of a bistable cantilever beam energy harvester exploiting vibro-impact effects

In this paper, a novel energy harvester is proposed by adding a barrier to a typical bistable energy harvester, which is modeled exploiting an equivalent single degree of freedom. By using Euler-Lagrange equations, mass, structural stiffness, magnetic force and electromechanical coupling coefficient of the harvester, are converted to an equivalent SDOF model. The frequency bandwidth of the system and the level of harvested power in impacting and non-impacting conditions are obtained. According to the numerical results, it is found by adding a barrier to a typical bistable energy harvester, the working frequency bandwidth of the system is increased tangibly. In fact, by vibro-impact phenomenon, the working frequency bandwidth and extracted power of the system are increased about 42.95% and more than 7 times, respectively. Additionally, the effects of stiffness and initial gap of the barrier are shown on frequency bandwidth of the harvester. It is observed that the gap distance has more effect on widening frequency bandwidth of the system against barrier stiffness. Finally, the effect of the electrical load resistance on the harvested power is discussed at various barrier stiffnesses and initial gap distances and finally the optimum values of the electrical load are provided for each condition.