Research On The Vibration Energy Harvesting Structure Using Piezoelectric Materials

Nowadays, the piezoelectric vibration energy harvesters are being widely used in many occasions, especially when the replacement of batteries is inconvenient, the ambient circumstances are adverse or the low power consumption is needed for normal operation. This is due to its excellent advantages, such as simple configuration, easy machining, free of pollution and so on. It utilizes the piezoelectric effect to harvest the vibration energy. In our study, based on the piezoelectric composite material, a modified structure and a new energy harvesting configuration are proposed and analyzed.Firstly, the poly(vinylidene fluoride)(PVDF) piezoelectric films are manufactured under the process guidance, which is simply described as filming-stretching-poling. Each possible factor in the manufacturing process that may influence the piezoelectricity is analyzed. Besides, the relationship between the open-circuit voltage of PVDF and its width and its piezoelectricity with nano-fiber material as fillers are studied.Secondly, based on the theory that the electromechanical coupling term is proportional to the difference of mode shape slopes at the starting and ending locations of the transducer, the conventional piezoelectric cantilever is modified to improve the difference. And then the equation of motion for the modified cantilever structure is established by using the Euler-Bernoulli beam theory to calculate its mode shape. The computation shows that its slope of the mode shape is really improved compared to the conventional ones. Moreover, this method is verified by experimental results.Finally, a new configuration harvesting the base vibration energy is designed utilizing the modified structure. Its theoretical model is presented on the basis of mass-spring-damping system. In addition, a parametric analysis is carried out to optimize the parameters. The calculation results indicate that, in order to get a high output power, the supporting lever should have high stiffness with light weight, and the modified cantilever should be set to about 0.16 times stiffness of the supporting lever at the same time.