Modeling And Characterization Of A Rotary Piezoelectric Generator Collecting Ocean Wave Energy

In order to solve the energy supply of wireless sensor network nodes,a rotating piezoelectric power generation device which can collect wave energy has been proposed.The device not only can obtain energy in low frequency environment,but also has frequency adjustable characteristics.In this paper,the piezoelectric wave energy structure of a rotating piezoelectric generator is introduced,the mathematical model of the rotating piezoelectric generator is established,and the frequency adjustable mechanism is discussed.Finally,based on the mathematical model of the rotating piezoelectric generator,the integral model of the wave energy device is set up and analyzed.The main contents are as follows:The proposed point-absorbing piezoelectric wave energy device with rotating piezoelectric generator consists of three parts,namely,first-order,intermediate and second-order.The first-stage energy conversion device converts wave energy into linear mechanical energy,whose main structure includes damper plate,floating and balance spring.The intermediate conversion component converts the mechanical energy from the form of straight line into the form of rotation with its main structure including gears and racks.The second-stage transducer is a non-contact rotating piezoelectric generator.Modeling and analysis of non-contact rotating piezoelectric generator are carried out,and relevant experimental platform is built to further verify the performance of the rotating piezoelectric generator.The results show that the optimal rotary frequency of the generator multiplied by the number of permanent magnets in the driving wheel array is equal to the first natural frequency of the piezoelectric bimorph beam.With the increase of driving wheel radius,the peak output voltage of piezoelectric bimorph beam decreases continuously.The larger the distance between driving wheel and bimorph beam,the lower the output voltage of bimorph beam is.According to the frequency adjustable mechanism of generator,a mathematical model is established,and an experimental platform is built to conduct the verification.The results suggest that when the output power of the generator exceeds 2.8 m W,and the distance d between permanent magnets is 30 mm,and the rotary angle range of the tuning magnet is 0-? degree,the rotary frequency range of the generator with tuning magnet is as 3.4 times as that of the generator without tuning magnet.The micro-amplitude wave theory and the advanced boundary element theory are applied to establish the hydrodynamic model of the first-order energy conversion device,and the multi-field coupling equation of the piezoelectric wave energy generator is established by combining the mathematical model of the intermediate conversion structure and the rotating piezoelectric generator structure.The optimum analysis results present that the optimum length of the damper plate and the optimum stiffness of the balance spring are 0.46 m and 434 N/m,respectively.This research provides a new idea for energy supply of ocean wireless sensor network nodes.