Modeling and Experimental Study of Vibration Energy Harvester with Triple-Frequency-Up Voltage Output by Vibration Mode Switching

Conventional wireless sensors rely on chemical batteries. Replacing or charging their batteries is tedious and costly in some situations. As usable kinetic energy exists in the environment, harvesting vibration energy and converting it into electrical energy has become a hotspot. However, the power output capability of a conventional piezoelectric energy harvester (PEH) is limited by its low operational frequency. This paper presents a new mechanism for achieving continuous triple-frequency-up voltage output in a PEH. The proposed system consists of a slender piezoelectric cantilever with two short cantilever-based stoppers. The piezoelectric cantilever undergoes a pure bending mode without contacting the stoppers. In addition, the beam switches into a new vibration mode by contacting the stoppers. The vibration modes switching yields reverses the signs of voltage outputs, inducing triple-frequency-up voltage output. Analytical and experimental investigations are presented, and it is shown that a significant triple-frequency up-conversion of the voltage output can be obtained over a wide frequency range. A peak power output of 3.03 mW was obtained. The proposed energy harvester can support a wireless sensor node.