Broadband power generation of piezoelectric vibration energy harvester with magnetic coupling

In this work, a magnetic coupling 2-degree-of-freedom bistable piezoelectric energy harvester was designed and developed. The device consisted of a primary beam with a magnet attached to the tip and a parasitic beam. The magnets between the primary beam and the pedestal generated nonlinear repulsive force. By controlling the distance between two magnets, the system could oscillate between two stable equilibrium points which allowed the device to exhibit broadband characteristics. Theoretical and experimental investigations of this energy harvester were presented over a range of excitation frequencies. Lumped-parameter nonlinear equations of the bistable Duffing oscillator with magnetic coupling were introduced to describe the broadband voltage response. Compared with the theoretical results, at an excitation acceleration of 3 m/s², it is experimentally verified that the proposed device achieved the operation frequency bandwidth adding up to 8 Hz at around the first and second resonance regions which was about 2.7 times higher than conventional 2-degree-of-freedom linear harvester one. In addition, energy harvesting efficiency could be improved by increasing the frequency bandwidth. The results of this work can be applied to optimize the design of piezoelectric energy harvester and harvest low-frequency vibration energy in the environment to supply power for sensor network nodes.