To enhance the output power and broaden the operation bandwidth of vibration energy harvesters (VEH), nonlinear two
degree-of-freedom (DOF) energy harvesters have attracted wide attention recently. In this paper, we investigate the
performance of a nonlinear VEH with magnetically coupled dual beams and compare it with the typical Duffing-type VEH
to find the advantages and drawbacks of this nonlinear 2-DOF VEH. First, based on the lumped parameter model, the
characteristics of potential energy shapes and static equilibriums are analyzed. It is noted that the dual beam configuration
is much easy to be transformed from a mono-stable state into a bi-stable state when the repulsive magnet force increases.
Based on the equilibrium positions and different kinds of nonlinearities, four nonlinearity regimes are determined. Second,
the performance of 1-DOF and 2-DOF configurations are compared respectively in these four nonlinearity regimes by
simulating the forward sweep responses of these two nonlinear VEHs under different acceleration levels. Several
meaningful conclusions are obtained. First, the main alternative to enlarge the operation bandwidth for dual-beam
configuration is chaotic oscillation, in which two beams jump between two stable positions chaotically. However, the
large-amplitude periodic oscillations, such as inter-well oscillation, cannot take place in both piezoelectric and parasitic
beams at the same time. Generally speaking, both of the magnetically coupled dual-beam energy harvester and Duffingtype
energy harvester, have their own advantages and disadvantages, while given a large enough base excitation, the
maximum voltages of these two systems are almost the same in all these four regimes.