A Frequency Tunable Energy Harvester Using Piezoelectric Cantilever Beam With Two Masses

In order to ensure the safety of moving vehicles, wireless sensors are usually installed on key structures, such as bridges. How to effectively power wireless sensor networks for long time becomes an urgent problem. Based on the piezoelectric effect, energy harvester can efficiently collect mechanical energy from external environment, which can power wireless sensor nodes. The highest energy harvesting efficiency can be achieved if the harvester works at its fundamental frequency. However, the fundamental frequency of traditional energy harvesters can’t be changed if they have been manufactured. Moreover, the adaptability to external environment is very poor. For the sake of solving these two issues, a tunable resonant frequency energy harvesting device with cantilever beam is designed. Its fundamental frequency can be adjusted to match the external vibration frequency. The harvester is then installed on a bridge to collect the vibration energy induced by moving vehicles. Hopefully, it can provide a new energy source for sensors used in the bridge health monitoring system.There are four chapters in this dissertation. The first chapter gives the background of this study and its significance for application. The second chapter introduces the theory and methods related to the work. In the third chapter, based on the Euler-Bernoulli beam theory and the piezoelectric constitutive equation, the output of harvester can be obtained, and parameters study is conducted to highlight the effect of various factors on power output or voltage output. In the fourth chapter, the forced vibration response of the beam subjected to a harmonic load is derived. Previous dynamic response of the bridge can be considered as the input of the piezoelectric energy harvester. Then the output voltage and energy of piezoelectric energy harvester under bridge have been given using the software ANSYS.This work provides a reference for further research on the design and application of piezoelectric energy harvester using for bridge systems.