Study On Nonlinear Flow-induced Vibration Piezoelectric Energy Harvesting

The small intelligent sensor terminals such as Wireless Sensor Networks（WSNs） and Micro Electro Mechanical System（MEMS）play an important role in people life and production activities.Traditional small sensor terminal has restricted its working cycle seriously due to the working life of the battery is limited.The flow-induced vibration energy harvester is an environmental energy harvesting device which transforms the flow energy in the environment into electric energy.It has lots of advantages,e.g.simple structure,low cut-in speed,green environment protection and so on.The design of self-power-supply can be realized by replacing the battery with the flow-induced vibration energy harvester to supply power to the small sensor terminal.However,due to the limitation of the volume of the energy harvester,the linear flow-induced vibration energy harvester has the disadvantages of low output power.Based on the above research background,this manuscript studies how to improve the energy harvesting efficiency of flow-induced vibration energy harvester through nonlinear magnetic field structure.In this manuscript,the electro-mechanical coupling models of different nonlinear flow-induced vibration energy harvester are established by Lagrange equation and Holkief circuit theorem,and then the models are verified by wind tunnel experiments and literature data.Based on the verified model,parametric study is carried out to analysis the influence of circuit load,wind speed,stiffness and damping on the energy harvester.The research contents and conclusions are as follows:（1）Based on the linear galloping energy harvester,a tristable structure is added to construct a tri-stable galloping piezoelectric energy harvester.The results show that there are three potential wells in the tristable galloping piezoelectric energy harvester.When the vibration of the bluff body changes from intra-well oscillation to inter-well oscillation,its vibration frequency and amplitude will change greatly.Compared with the linear galloping energy harvester,the cut-in speed of the tristable galloping piezoelectric energy harvester is reduced by 33%,and the root mean square output voltage is increased by 88.6%.（2）Based on the double column galloping piezoelectric energy harvester,a dynamic magnetic coupling galloping piezoelectric energy harvester can be constructed by adding mutual repulsive magnets.The results show that due to the influence of nonlinear magnetic force,the cut-in speed of the 1^stand the 2^ndbeam of the dynamic magnetic coupling galloping piezoelectric energy harvester are consistent,and its output and cut-in speed are better than that of the linear galloping piezoelectric energy harvester.At the same time,by reducing the beam stiffness ratio f,selecting the appropriate effective mass ratioμand increasing the bluff body width h^*,the performance of the energy harvester can be improved.（3）By changing the load interface and electro-mechanical coupling strength,the output of the nonlinear galloping piezoelectric device can be improved.It is found that the output of the harvester with DC circuit interface is higher than that of the harvester with AC circuit interface under higher load,but the output of the harvester under optimal load resistance is lower than that of the energy harvester with AC circuit interface.The output voltage of the energy harvester with SCE circuit interface is relatively stable,and its overall performance is better than that of AC circuit interface and DC circuit interface.It should be noted that the bis-table energy harvester with SCE circuit interface has a large transition range.In addition,the output of the energy harvester can be improved by adjusting the electro-mechanical coupling strength.