Modeling and experimental investigation of a novel bistable two-degree-of-freedom electromagnetic energy harvester

Abstract

The working bandwidth is an attractive aspect of vibrational energy harvesters. This paper investigates the energy harvesting enhancement of a two-degree-of-freedom (2-DOF) bistable electromagnetic energy harvester (BEEH). The bistability is achieved by designing the interaction between magnetic repulsive and attractive forces. The nonlinear restoring force is adding in one of the degrees to construct two types of 2-DOF-BEEHs. The output voltages and powers of the two types of the 2-DOF-BEEHs are discussed and compared after analyzing the kinetic equations of the harvesters. The theoretical model of the 2-DOF-BEEH is established and the analytical solution is obtained by applying the harmonic balance method (HBM). Several parameters such as mass ratio, frequency ratio, potential well and excitation amplitude are discussed. Theoretical and experimental efforts are carried out to verify the energy harvesting performance of the 2-DOF-BEEH. The results indicate that a bigger mass ratio can enhance the amplitude of the two resonance peaks while a smaller frequency ratio leads to a better performance. Moreover, the two resonant peaks will also be influenced by the shapes and depths of potential well. A larger initial excitation displacement can enhance the first-order resonance peak of the 2-DOF-BEEH.