Research On Micro Piezoelectric Energy Harvester With Folded Back Beam Structure Based On Fluid Environment

In order to meet the self-powered needs of the sensor system in a fluid environment with a variable range of fluid velocity and a limited space,a new miniature piezoelectric energy harvester with a three-degree-offreedom return beam based on vortex shedding induced vibration By adjusting the natural frequency of the device,the piezoelectric vibrator is adapted to the variable flow velocity environment of different flow velocity ranges,the working bandwidth of the energy harvester is widened,and the energy supply requirements of the wireless sensor system in the variable flow velocity environment are realized.The main research contents and experimental results are as follows:(1)Structure and scheme design of piezoelectric energy harvester with micro-folded beam structure.According to the characteristics of fluid velocity,temperature and pressure in the pipeline,the corresponding piezoelectric fluid energy harvester structure is designed to enable it to collect the energy in the fluid in an efficient manner.The eddy current distribution characteristics of the flow field behind the bluff body have been analyzed,and the structure of the piezoelectric energy harvester has been designed to form vortex-induced resonance.The characteristics of the firstorder resonance mode and multi-order vibration mode are compared and analyzed for the piezoelectric energy harvester to determine its structural scheme.(2)Theoretical modeling and simulation analysis.Based on the piezoelectric effect,the mathematical model of the system is established through the theory of fluid-solid coupling and electromechanical coupling.The flow field distribution in the region is analyzed theoretically.The output performance of the system and its influencing factors are analyzed theoretically.The frequency characteristics and resonance modes have been simulated and analyzed;the micro-return beam structure piezoelectric energy harvester has three resonance frequencies under 3.5-7.5 Hz lowfrequency vibration and can generate three output peaks.At the same time,compared with the traditional single cantilever piezoelectric energy harvester,it can cover a wider frequency band.Produces higher output peaks.(3)Design the fabrication process of the piezoelectric bimorph vibrator with micro-folded beam structure,and prepare prototype of the harvester.It is mainly composed of piezoelectric bimorph,vibration plate,excitation plate,mass,and lead wire.The key process steps of the preparation include mechanical grinding and polishing,sputtering electrodes,bonding processes,and packaging processes.The vibration performance test platform and underwater test system are set up,and the operation mechanism of the test system is introduced.(4)Shaking table test and underwater test.The experimental results show that the piezoelectric energy harvester with micro-folded beam structure will have output voltage peaks at flow rates of 0.35 m/s,0.55 m/s,and 0.75 m/s.When the velocity is 0.55 m/s,the output voltage will be the maximum,and the voltage and power will be 17.2 V and 81.2 μW respectively.Compared with the traditional single beam,the micro-folded beam piezoelectric energy harvester can obtain higher voltage and power in the low frequency flow range corresponding to 3.5-7.5 Hz,Widen the operating frequency band and adapt to changes in the environmental vibration frequency.