Nonlinear dynamics of a pendulum-beam coupling piezoelectric energy harvesting system

To improve the transform efficiency of vibration energy, we proposed a novel energy harvester composed of a piezoelectric cantilever beam and a pendulum. Under horizontal excitations, the pendulum oscillation will lead to a fluctuation in the tension force of the rope and to a change in the compressive force acting on the beam, which could be employed to make the beam reach dynamic buckling. This buckling could lead to a large amplitude vibration and high voltage output. First, the kinetic energy and potential energy of the system are obtained; then the electromechanical coupling equations are derived based on the extended Hamilton's principle. Furthermore, the dynamical responses of the system subjected to both harmonic and random excitations are explored. The influence of parameters on the performance is thoroughly discussed. The simulation results proved that large pendulum mass and large initial pendulum angle could make the beam buckle more easily, which is beneficial for converting broadband ambient vibration energy. It is also found that the optimal pendulum length could bring about large-amplitude vibrations and generate a considerably high output voltage.