Research On Low-frequency And Wideband Vibration Energy Harvester Based On Piezoelectric Effects

Recently, integrated circuit system, MEMS devices and portable electronic devices are becoming more and more attractive, and widely used in the human body health testing system, environment control system, military security and field tracking application system and so on. However, for wireless sensors which are applied in special areas, for example in the wild, there are inherent defects in traditional energy supply mode, such as battery and power lines:big volume, limited life, need to repeat charging. The new nuclear cell has the advantages of small volume, long power life. But it has not widely used due to the radioactive and it needs special protective measures. Hence, energy harvesting from ambient vibration have been investigated extensively to power electronic equipment of special environment. Environmental vibration energy harvesting technology is mainly divided into three types:piezoelectric type, electromagnetic type and electrostatic type. Compared with the other two forms of harvesting energy, in view of the advantages of high electromechanical coupling and no requirement for external voltage source, piezoelectric mechanical vibration energy harvesters have attracted much more attention.The ambient vibration frequencies that the harvesters are subjected to are mainly distributed in the low frequency (<200Hz). While most of the energy harvester working frequency lie in a narrow range. Should environmental vibration frequency doesn’t match the natural frequency, and then a great drop will occur in output power results. Therefore, how to design the energy harvester to match the multi-source vibration environment becomes the main point of vibration energy harvesting technology. In order to solve this problem, this paper has designed two kinds of energy harvesters for low-frequency and wideband vibration to realize highly efficient collection. The main research works are as follow:(1) Comparing the advantages and disadvantages of various energy acquisition methods to achieve the most suitable for environmental vibration energy harvest, that is piezoelectric vibration energy harvesting. Study the main method and the development status of energy harvester for low-frequency and wideband vibration.(2) Analyze the theory of piezoelectric vibration energy harvesting; discuss the traditional cantilever energy conversion model, the spectrum characteristics, and the defects for energy harvesting. Introduce the finite element simulation software, and set up the experimental test platform.(3) Design the first kind of energy harvester for low-frequency and wideband vibration, first and second order transmission piezoelectric vibration energy harvesters. The Structure, working principle, mathematical modeling and simulation are introduced. The results show that the energy harvester has the low frequency and wideband characteristics, especially the second-order transmission energy harvester, which is more suitable for low frequency random vibration environment energy harvest, appeared two peaks below50Hz, band broadening50%.(4) Design the second kind of energy harvester for low-frequency and wideband vibration, flexible frame based interdigital energy harvester for low-frequency and wideband vibration. The Structure, working principle, mathematical modeling and simulation are introduced. Based on the theory and simulation, design experiment project for testing, the test results fit well with the simulation, which show that the energy harvester has the low frequency and wideband characteristics, especially the proposed device with quintuple piezoelectric cantilever beams, shows a560%increase in bandwidth below80Hz comparing to the traditional cantilever.