This paper proposes the theoretical model and experimental investigations of a broadband piezoelectric based vibration energy harvester with a triple-well potential induced by a magnetic field. The mathematical model is derived from the energy method to describe the response characteristics of nonlinear tristable energy generators. The parameters of the linear energy harvesting system without magnetic force actuation are obtained through intelligent optimization of the minimum error between numerical simulations and experimental responses. The equivalent nonlinear restoring force of the tristable oscillator is experimentally identified as a high order polynomial. Numerical simulations and experiments are performed at different harmonic excitation levels ranging from 1 to 20 Hz. The results verify that the identified electromechanical model can describe the dynamic characteristics of broadband tristable energy harvesters. Furthermore, in comparison to bistable nonlinear energy oscillators with deeper potential well, the tristable arrangement passes easily through potential wells for generating higher energy output over a wider range of frequency.

Broadband tristable energy harvester: Modeling and experiment verification