Basic Theories And Experimental Studies Of Nonlinear Tri-stable Piezoelectric Vibration Harvester

With the rapid development of MEMS technology and wireless sensor network,traditional batteries can not meet the demands of the low powered electronic devices due to their low utilization rate,large quality,large size and limited functional life,and so on.Therefore,it is necessary to seek a sustainable and environmentally friendly new energy to replace batteries.Due to its ubiquitous and pollution-free advantages,vibration energy has become a new energy to replace batteries.However,how to collect and efficiently use the vibration energy has become a hot research topic.Piezoelectric vibration energy harvester is novel electromechanical device that can be used to harvest and convert environmental energy into electrical energy with the piezoelectric effect and then supplying power to some low-power electronic devices.The existing piezoelectric vibration energy harvester are mainly linear resonant oscillators based on piezoelectric cantilever beams,which have the advantages of simple structure,easy implementation and high energy conversion efficiency,but also have the disadvantages of narrow working frequency band width and low harvesters efficiency.In addition,compared with mono-stable and bi-stable energy collectors,tri-stable piezoelectric energy harvesters have better output characteristics and are more suitable for the power supply of micro-power electronic products.Therefore,how to broaden the working bandwidth of piezoelectric vibration energy harvester and improve the efficiency of energy acquisition is the main problem that needs to be solved urgently.Ther tri-stable piezoelectric cantileve energy harvester based on magnet coupling is the main research structure at present.Substantial numbers of research results show that this kind of energy harvester has higher output performance and wider working frequency band width.However,the application of the harvester is severely restricted in some situations where magnetic interference is strong,and even in human or animal bodies.Therefore,a novel tri-stable piezoelectric vibration energy harvester based on two ilinear elastic elements coupling is proposed in this paper.The nonlinear restoring force between the two springs is used to make the harvester vibrate nonlinearly,so as to improve the output efficiency of the harvester and expand the frequency band.The main research work of this paper includes:(1)Firstly,the research background and significance of piezoelectric vibration energy harvester are introduced,as well as the research status and existing problems at domestic and foreign.Then the main research content and innovation of this paper are put forward.In addition,in order to facilitate the understanding of the research work in this paper,basic theories and knowledge related to the research content of this paper are briefly introduced,including piezoelectric theory,piezoelectric vibration model,cantilever bending vibration theory and nonlinear vibration theory.(2)The structure model,research results and existing problems of magnetic-coupled nonlinear piezoelectric vibration energy harvesters are introduced.A novel nonlinear tri-stable piezoelectric vibration energy harvesters based on the coupling of two ilinear elastic elements is proposed.Subsequently,the nonlinear elastic model and the lumped parameter dynamics model of the new type of piezoelectric vibration energy harvesters are established.After dimensionless treatment,the equation is solved by 4-5 order Runge Kutta algorithm and harmonic balance method,and then the system is simulated in time domain and frequency domain to analyze the influences of system parameters on the static and dynamic characteristics of the energy harvester.The influences of the acceleration amplitude of the external excitation signal,the distance between the springs,the distance between the end mass block and the spring on the system characteristics are discussed emphatically,and compared with the mono-stable and bi-stable characteristic systems.(3)The experimental prototype of the new tri-stable piezoelectric vibration energy harvester is developed,and the experimental test platform is built.The correctness of the theoretical model and simulation results were verified according to the experimental data.At the same time,the influence of different excitation frequencies on the system response characteristics was studied experimentally,the change of output voltage under different load resistances was compared,and the relationship between the excitation acceleration and the motion velocity of the terminal mass block was analyzed.It is found that the energy harvester has a wider effective working frequency band and a higher output voltage in the case of tri-stable motion,and it can generate large period motion under low-frequency and low-amplitude excitation,achieving the expected research effect.Finally,this paper summarizes the content of the research and puts forward the prospect of the future research.