Research On Low-Frequency And Multi-Directional Piezoelectric Vibration Energy Harvesting

Harvesting energy from the surroundings is a non-polluting,promising approach to replace the traditional chemical batteries in constantly emerging low-power systems and wearable electronics.Piezoelectric energy harvesting technology has become a research hotspot for its high output energy density,easy miniaturization and easy integration.In order to efficiently collect the variable vibration energy in the daily life,this thesis proposed a multi-direction piezoelectric energy harvester with a wide bandwidth and low working frequency,which is distinguished by the multiple working modes of the U-shaped beam and the high capacity of the pendulum in collecting arbitrary vibrations.Based on the U-shaped beam,this design expands the pendulum structure that can sense vibration energy in any direction,which realizes the mechanical energy transformation from the pendulum structure to the U-shaped beam.It has more resonant modes available and the ability to adapt to the variable vibration energy in the everyday environment.Then,the structural characteristics are proved by theoretical simulation and experimental verification.Experimental results show that the energy harvester generates three effective voltage peaks in the frequency range of 0-25 Hz,the maximum output open circuit voltage is 13 V and the maximum output power is 306.94 μW.Finally,the capacitor is charged by collecting the vibration energy of the human body.The voltage over capacitor is raised to 5.5 V,storing about 0.3 m J energy in the capacitor.Aiming at the defects of U-shaped beam pendulum-structure in installation,the structure is optimized and improved.We proposed a multidirectional piezoelectric vibration energy harvester based on U-shaped structure with Cross-connected beam.Benefitting from the bidirectional capacity of U-shaped beam and additional bending mode induced by crossconnected configuration,the proposed structure can well capture the vibrations in 3D space.In addition,The structural features are evaluated by finite element simulation and verified by experiments.The experimental results show that the configuration has superior performance than the piezoelectric vibration energy harvester based on U-shaped beam pendulum-structure.Compared with the piezoelectric vibration energy harvester of Ushaped beam pendulum-structure,the output voltage of the harvester is increased by 360%,and the installation mode has higher flexibility.Furthermore,charging capacitance experiment and power supply experiments prove the feasibility of this energy harvester in supplying power for wireless sensor devices.In this thesis,two piezoelectric energy harvesters can effectively collect the variable vibration energy in the environment.These two energy harvesters can not only be used to collect vibration energy generated by human body,but also have great application potential in bridge and vehicle vibration energy collection.