This paper presents a type of vibration energy harvester combining a piezoelectric cantilever and a single degree of freedom (SDOF) elastic system. The main function of the additional SDOF elastic system is to magnify vibration displacement of the piezoelectric cantilever to improve the power output. A mathematical model of the energy harvester is developed based on Hamilton's principle and Rayleigh-Ritz method. Furthermore, the effects of the structural parameters of the SDOF elastic system on the electromechanical outputs of the energy harvester are analyzed numerically. The accuracy of the output performance in the numerical solution is identified from the finite element method (FEM). A good agreement is found between the numerical results and FEM results. The results show that the power output can be increased and the frequency bandwidth can be improved when the SDOF elastic system has a larger lumped mass and a smaller damping ratio. The numerical results also indicate that a matching load resistance under the short circuit resonance condition can obtain a higher current output, and so is more suitable for application to the piezoelectric energy harvester.
This study presents a new design of a piezoelectric-electromagnetic energy harvester to enlarge the frequency bandwidth and obtain a larger energy output.This harvester consists of a primary piezoelectric energy harvesting device,in which a suspension electromagnetic component is added.A coupling mathematical model of the two independent energy harvesting techniques was established.Numerical results show that the piezoelectric-electromagnetic energy harvester has three times the bandwidth and higher power output in comparison with the corresponding stand-alone,single harvesting mode devices.The finite element models of the piezoelectric and electromagnetic systems were developed,respectively.A finite element analysis was performed.Experiments were carried out to verify the validity of the numerical simulation and the finite element results.It shows that the power output and the peak frequency obtained from the numerical analysis and the finite element simulation are in good agreement with the experimental results.This study provides a promising method to broaden the frequency bandwidth and increase the energy harvesting power output for energy harvesters.
