Abstract: A hybrid piezoelectric device combining a tri-stable piezoelectric energy harvester (TPEH) with a linear amplifier and nonlinear magnetic force is presented to enhance the harvesting ability of the low-orbit vibration energy. The linear amplifying mechanism (LAM) composed of a mass and spring is placed between the TPEH and the base to amplify the low-orbit vibration and provide the TPEH enough kinetic energy to overcome the potential barrier, which make the TPEH easily jump to the high-orbit oscillation, resulting in an even better operating bandwidth and higher power generation. The nonlinear electromechanical model describing the dynamic responses of the presented harvester is derived. The effects of the mass ratio and stiffness ratio on the dynamic performances of the hybrid energy harvester are numerically investigated with dynamic bifurcation diagrams method. The results show that the presented harvester has wider frequency bandwidth and higher power generation by properly selecting the mass ratio and stiffness ratio, and it can more easily snap-through from low-orbit oscillation to high-orbit oscillation to reach larger dynamic response at lower excitation levels. Experiments are conducted to validate the simulations, and the experimental results are in reasonable agreement with the theoretical results. Compared to the traditional tri-stable piezoelectric energy harvester, the working frequency band of the compound TPEH enlarges from 3～14 Hz to 2～21.5 Hz, and the excitation acceleration required to jump from low-orbit vibration to high-orbit vibration decreases from 13.5 m/s² to 5.8 m/s².

Key words: tri-stable energy harvester, linear amplifying, nonlinear magnetic force, energy harvesting, dynamic bifurcation