Theoretical And Experimental Research On Right Angle-Shaped Piezoelectric Cantilever Beam Vibration Energy Harvester

Wireless sensor network nodes are generally powered by chemical batteries, the battery energy seriously affects the working life cycle of wireless sensor networks. Sustainable power supply has become a practical problem to be solved urgently. Chemical batteries are generally faced with regular to charge or replace, which will cause the waste of human resources, material resources and environmental pollution, and other issues, the continuous development of modern integrated circuit technology, the application of energy harvesting technology for sensor nodes to provide energy, so as to achieve the extension of their life, no longer frequent replacement battery. The application of energy harvesting technology can realize the continuous work, environmental protection, clean, save cost and so on, it is a key technology to solve the self power supply of wireless sensor networks. By using the piezoelectric effect, the vibration energy can be converted into electrical energy of the piezoelectric material working environment. This new technology can realize the self-power supply of network nodes, and get rid of the limited working time, pollution and recycling of chemical battery. It is a kind of clean and durable new energy harvesting technology. Now, energy harvesting technology has become a very important research topic in China and foreign countries.There are many kinds of energy harvesters, in which the piezoelectric vibration energy harvester is the most promising one, the reason is that the vibration energy not only exists in the environment but also the output power density is large, it has the advantages of simple structure and easy integration. Typically, piezoelectric vibration energy harvester is bimorph cantilever structure with a block at the tip. However, the structural defects are single work frequency, narrow-band frequency and low energy harvest efficiency. Therefore, broadening the bandwidth of the resonant response frequency is the key factor to improve the efficiency and the best output performance of the piezoelectric vibration energy acquisition.In this paper, a new type of piezoelectric cantilever vibration energy harvester is presented based on the theory of piezoelectric theory, a vertical auxiliary bimorph cantilever beam is added at the free end of the horizontal beam and a mass block is fixed at the top end of the vertical beam. A right angle-shaped piezoelectric vibration energy harvester is composed by both coupling interactions. According to the principle of the piezoelectric effect established the theoretical model of the device vibration energy conversion, to broaden the work frequency band as the goal, optimized by adjusting the horizontal or vertical piezoelectric bimorph cantilever beam structure size and material parameters, effectively narrowed the frequency spacing between first two modes of right angle-shaped piezoelectric vibration energy harvester, formed a low frequency wide band. This structure effectively solves the problems above. The main research works of this paper include:(1) The right angle-shaped broadband piezoelectric vibration energy harvester structure is designed, ANSYS software is adopted to establish finite element electromechanical coupling model of the right angle-shaped cantilever energy harvester, simulate and analyze impacts of various parameters of right angle-shaped piezoelectric vibration energy harvester on resonance frequency, vibration characteristics, electrical output response, the optimal structure size and design parameters are obtained.(2) Combined with the use of piezoelectric theory, Euler Bernoulli beam vibration theory and Hamilton’s theory, the electromechanical coupling dynamic model of a right angle-shaped piezoelectric vibration energy harvester is established, and the resonance frequency, the characteristic equation and the energy acquisition and output equations are derived. By using MATLAB software get the key factor that influence of vibration frequency, amplitude frequency and electrical output response.(3) Developed right angle-shaped broadband piezoelectric vibration energy harvester prototype, built a test platform, by comparing the experimental results with the theoretical model and simulation results analysis, to verify the correctness of the theoretical analysis results.(4) The research of this paper is summarized and prospected, and puts forward the next steps of research work.