Design and characteristic analysis of a novel deformation-controllable piezoelectric vibration energy harvester for low frequency

Vibration energy harvesting using the piezoelectric effect is becoming a promising solution to the sustainable green power source for low-power portable and wireless electronics. To harvest low-frequency vibration energy and prevent the damage of piezoelectric vibrator due to the excessive deformation, a novel deformation-controllable piezoelectric vibration energy harvester (D-CPVEH) by using a wedge cam to limit the maximum deformation of the cantilevered piezoelectric vibrator is proposed in this paper. The cam structure can drive the pre-bending piezoelectric vibrator to produce a controllable-amplitude and unidirectional deformation, thereby improving the reliability of the harvester significantly. To verify the feasibility of the proposed principle and design, theoretical analysis and numerical simulation are firstly performed, and then the influences of system parameters on the dynamic response of the D-CPVEH are analyzed in terms of amplitude ratio of the cam and deformation of the vibrator. Afterwards, a prototype is fabricated and tested in terms of frequency response characteristics. The simulation and experimental results show that the maximum deformation of the piezoelectric vibrator can effectively be limited by introducing the cam structure. Besides, it demonstrates that the spring stiffness, additional mass, cam lift, cam angle and excitation frequency exert a significant effect on the amplitude ratio of the cam, the deformation of the piezoelectric vibrator, the output voltage and the maximum voltage of the harvester, and the optimal operating bandwidth. The maximum generated voltage increases while the corresponding optimal operating bandwidth decreases with the increase of the cam lift. It is found that the maximum voltage is basically independent of other structural parameters except for the cam lift. Furthermore, the optimal operating bandwidth can be effectively adjusted by the spring stiffness, additional mass and cam angle to adapt to the broadband low-frequency vibration environments. The testing result shows that the D-CPVEH can achieve the maximum power of 2.58 mW at 5.5 Hz with the optimal load resistance of 30 kΩ.