Study On Multi-direction And Wideband Vibration Energy Harvester

It puts forward new requirements for the development of wireless sensor network(WSN) technology along with the rapid development of the chip and ultra-low power consumption integrated circuit. One of the problems is to use sustainable power instead of the traditional chemical battery for the wireless sensor network node, namely the realization of the self-energizing of WSN. This is because the distribution of wireless sensor network node is wide and many node work in the harsh environment. It is bound to cause the waste of a lot of labor and material resources if replace the batteries of the node using the traditional method. Therefore, we need to seek the sustainable supply method in order to prolong the life of WSN and make it work more stable.Energy harvesting technique is the most potential method to solve the problem of the self-energizing of the wireless sensor network node. In recent years, the vibration energy harvesting technology has become a hot research topic due to the widespread and high power density of the vibration. Many researchers designed the vibration energy harvester based on the piezoelectric effect and this kind of harvester is stable, easy-making and have no pollution. But most of them only have high output at the resonant frequency, once deviate from the resonant frequency, the output drop sharply. Furthermore, they are only sensitive to the vibration of a direction. So the design of harvester that is wideband and responds to multi-direction can not only adapt to the real environment but also improve the efficiency due to the vibration in the environment has the characteristic of wideband and multi-direction.This paper designs a V-type structure energy harvester based on the traditional piezoelectric cantilever structure. The V-type harvester is composed of two piezoelectric beams with a certain angle. It can achieve the effect of wideband as the close of the first two order resonance frequency and response the vibration of two directions at the same time. First of all, deduce the voltage response equation of the bimorph with a tip mass using the Euler-Bernoulli equation, the piezoelectric equation and the Kirchhoff’s law and deduce the V-type harvester voltage response equation based on the mathematical model of the bimorph. Then simulate the output of the V-type structure using the Matlab software and simulate the vibration modal of it using the finite element simulation software COMSOL essentially explaining the circuit connection to improve the efficiency of the harvester. Put forward a kind of storage interface circuit for multiple piezoelectric element. Finally, make the V-type structure harvester, test fixture and energy storage interface circuit and test the performance of the harvester when its angle is 45°, 90°, or 135°comprehensively. The experimental results show that there are two peaks of the open circuit output voltage in the frequency of 0Hz ~60Hz when the angle of V-type harvester is 90°or 45°whether excite in the Z direction or in the Y direction. As a result, it could broaden the working frequency band and reach the maximum output power through matching the resistance when excite at the above frequency of the peak open circuit output voltage. In addition, the test shows that the energy storage interface circuit could output the stable dc electricity.