Design And Research On Multi-degree Of Broadband Energy Harvester

During the development of the IOT(Internet of things technology),the traditional battery power supply is difficult to supply power for the IOT terminal nodes due to its maintenance and replacement difficulties,especially network nodes in remote areas or implantable electronic devices.And it is possible to harvest energy such as wind energy,solar energy,vibration energy,etc.to supply power to the network node terminals.Harvesting vibration energy can ensure a stable power supply for electronic equipment,due to the generation of vibration energy is less affected by environmental factors such as climate and temperature.Therefore,vibration energy harvesting technology has attracted more and more attention.Most of the vibration signal was low-frequency random vibration signal in the environment.Harvesting and converting vibration energy into electric energy is an effective way to solve the problem of long-term reliable power supply for wireless sensor network nodes.The piezoelectric vibration energy harvester is a promising energy harvester due to its simple structure,high energy harvesting efficiency and large response range.Traditional single-degree-of-freedom piezoelectric energy harvester with high natural frequency and narrow bandwidth and often can't work reliably in practical engineering applications.Therefore,it is very important for the practical application of the piezoelectric energy harvester that makes effort to reduce the natural frequency of the piezoelectric energy harvester and broaden its working bandwidth by optimizing the harvester's structure.In this paper,two multi-degree-of-freedom energy harvesters and a based on pre-stress beam nonlinear piezoelectric energy harvester are designed.The theoretical modeling of the proposed energy harvesters was built,and numerical simulation and experiment is conducted to verify the method.Firstly,the electromechanical coupling dynamics model of Z shape and P shape piezoelectric energy harvesters is established based on the Euler Bernoulli beam theory and piezoelectric equation.Secondly,the simulation of the above two multi-degree-of-freedom energy harvesters and two typical traditional energy harvesters is carried out by the finite element method.Finally,an experimental platform based on Lab View is built to test the harvester's performance and verify the theory and simulation.Besides,this paper has done the research of the pre-stress beam to improve the energy harvesting efficiency and working bandwidth of the single-degree-o f-freedom piezoelectric energy harvester.The simulation results show that the two multi-degree-of-freedom energy harvesters can achieve multi-modal response under low frequency.Under random excitation,the harvesting performance of the two multi-degree-of-freedom energy harvesters is better than the traditional piezoelectric energy harvesters.According to the experimental results,compared with the traditional two-degree-of-freedom energy harvester,the charging efficiency of the Z-type energy harvester is improved by 71.12%,and the charging efficiency of the P-type energy harvester is improved 15.95%under the random vibration test.In the test of the energy harvester based on pre-stress beam,compared with the piezoelectric energy harvester without axial tensile force,the capacitor's charged voltage by the piezoelectric energy harvester with 5.9N axial tensile force is improved 1.55V.As the experimental results show,under random excitation,compared with the two traditional energy harvesters,the energy harvesting performance of the two multi-degree-of-freedom energy harvesters is improved greatly.And,it is really effective for improving the harvesting performance of the traditional single-degree-of-freedom energy harvester by pre-stress beam theory.It is meaningful for practical engineering application.