Analysis of nonlinear spring arm for improved performance of vibrational energy harvesting devices

Recently, a number of attempts have been made to increase the operational bandwidth of the energy harvesting devices. Nonlinear mechanisms are one of them. In this paper, we report design and analytical formulation of stretching strain of an electromagnetic energy harvester on FR4 material under large deformation of the spring arms. It is found that nonlinearity has an inverse square dependence on thickness of the arms. Numerical solution of a monostable Duffing oscillator that governs the dynamics of such a large deformed nonlinear energy harvester showed that with decrease of load resistance, the average power output increases, where the output response depends strongly on the input force. For small input acceleration, the desired large amplitude vibration does not come into play and the response becomes linear. However, for higher input acceleration nonlinearity appears and the operational bandwidth increases, at the same time, output power level also increases.