Limit Cycle Oscillations of a Nonlinear Piezo-magneto-elastic Structure for Broadband Vibration Energy Harvesting

Abstract

Vibration-based energy harvesting has been investigated by several researchers over the last decade. Typically, devices employing piezoelectric, electromagnetic, electrostatic and magnetostrictive transductions have been designed in order to convert ambient vibrations into electricity under resonance excitation. Regardless of the transduction mechanism, a primary issue in resonant energy harvesters is that the best performance of the device is limited to resonance excitation. That is, the power output is drastically reduced if the excitation frequency slightly deviates from the resonance frequency of the generator. In order to overcome this issue of the conventional cantilever configuration, a nonlinear piezomagneto- elastic energy harvester is introduced in this paper. First the electromechanical equations describing the nonlinear system are given along with theoretical simulations to demonstrate the existence of large-amplitude limit cycle oscillations (LCO) at different frequencies. In agreement with the theory, the experiments show that the transient chaotic vibrations of the generator can turn into large-amplitude LCO on a high-energy orbit, which can also be realized by applying a disturbance to the structure oscillating on a low-energy orbit around one of its foci. It is shown experimentally that the open-circuit voltage output of the piezo-magneto-elastic configuration can be three times that of the conventional piezo-elastic cantilever configuration without magnetic buckling. Therefore the device proposed here generates an order of magnitude larger power output over a range of frequencies. The magneto-elastic structure is discussed here for piezoelectric energy harvesting and it can also be utilized to design enhanced energy harvesters using electromagnetic, electrostatic and magnetostrictive transductions as well as their hybrid configurations.