Study On Hybrid Piezoelectric-electrostatic Vibration Energy Harvester Using Non-linear Technology

The rapid growth of Internet of Things technology and low-power electronic products have lead to the wireless sensor networks being widely used in environmental monitoring?structural health monitoring?implantable therapy?traffic monitoring and so on.These applications require wireless sensor networks with long-life,high-reliability and self-powered supply technology.Due to the short-lifespan,large-volume and environmental pollution,traditional chemical battery was not suitable for wireless sensor networks.Therefore self-powered device using energy harvesting techniques have been a research hotspot recently.Energy harvesting is a method to generate electrical power from environmental energy sources such as solar,thermal,wind,vibration,radio frequency(RF)energy,and so on.Among these energies,vibration-based energy harvesting has significant advantages in working environment?working hours and power density.Generally,vibration energy harvesting techniques are generally electromagnetic,piezoelectric?electrostatic,frictional energy harvester.Within the four conversion techniques,piezoelectric energy harvester has been widely studied due to its high output voltage and electrostatic energy harvester was concerned due to its good compatibility of MEMS processing.Development of vibration energy harvesting and power consumption reducing in Wireless sensor node make the energy harvesting technology using in sensor networks possible.However,the low effective output power and narrow work frequency band limited the application of the vibration energy harvester.Optimizing the vibration energy harvester in power and frequency band become the research hotspots.In order to increase the output power and broaden work frequency band,this paper presented a hybrid piezoelectric-electrostatic vibration energy harvesting technology using non-linear technology.The nonlinear technology can broaden the work frequency band,while piezoelectric-electrostatic hybrid outputs can increase the output power.The electromechanical model was established and simulated by Matlab/Simulink,and the results was verified by the experiment of prototype in this paper.Through the same method,the electrical output characteristics and nonlinear response characteristics was studied in the nonlinear piezoelectric vibration energy harvester,nonlinear electrostatic vibration energy harvester and the hybrid vibration energy harvester.The main innovations in this paper are summarized as follows:(1)The electromechanical model of piezoelectric-electrostatic vibration energy harvester based on non-linear technology was established in this paper.This model can be used to predict the output power,output voltage,and analysis the relationship between load,excitation amplitude,damping,nonlinearity and electrical output characteristics of the non-linear vibration energy harvesters.For the hybrid piezoelectric-electrostatic vibration energy harvester,the optimal parameters and applicable environment were determined.Finally,a large prototype was used to verify the model.(2)Duffing nonlinearity and impact nonlinearity were introduced into the hybrid piezoelectric-electrostatic vibration energy harvestier by designing structural.The nonlinear technology can broaden the working band width with increasing the output power density.In this paper,Duffing nonlinearity and impact nonlinearity were analyzed theoretically.The influence of structural parameters on the nonlinearity was modeled and analyzed.Through modelin and simulating,the device's optimal working range was determined.(3)A structure that can integrate piezoelectric and electrostatic mechanisms was designed.The structure was based on the out-of-plane gap varing type,in which the vibration-absorbing component adopts a bridge structure with an "L" beam.The folded beam not only decreasing the resonant frequency but also increases the amplitude of the vibrator.In addition,the experimental results in the paper shows that the geometric nonlinearity of the structure can effectively improve the device operating bandwidth.