Numerical analysis of an electromagnetic energy harvester driven by multiple magnetic forces under pulse excitation

Abstract

This paper presents a numerical analysis model for an electromagnetic energy harvester that is driven by multiple magnetic forces under pulse excitation. The energy harvester consists of a tube with magnets on both ends and a shuttle magnet moving inside. It converts pulse excitation to oscillation of the shuttle magnet with higher frequency and amplitude. A numerical model was developed to model operation of the energy harvester. The model correlates analytical calculation of magnetic forces and simulation results of magnetic field in Maxwell. Operation of the structure was then analysed using fundamental equations of motion in the time domain. A prototype was fabricated and two example scenarios were tested to verify the numerical model. Experimental results in both scenarios were found to agree with results obtained from the numerical analysis. It was also found in the numerical analysis that initial positions of the end magnets with respect to the shuttle magnet are crucial to the performance of the energy harvester. If the distance between the end magnet and the shuttle magnet reduces, oscillation of the shuttle magnet will last longer but have smaller amplitude. If such distance reduces below a threshold, the shuttle magnet cannot move at all. Furthermore, friction between the shuttle magnet and the tube also affects its oscillation. The lower the friction becomes, the longer the oscillation can last and the higher the oscillation amplitude can be.