Study On Broadband Nonlinear Vibration Energy Harvester

With the construction and development of digital society,the consumption of energy is increasing with the large-scale application of modern information technology such as digitalization,networking,Internet of things and big data.Traditional fossil fuels,such as oil and coal,are seriously polluted and facing the severe problem of exhaustion.Coupled with the increasingly stringent global carbon emissions,green energy is becoming increasingly important.Energy harvesting technology is the key field of distributed energy after hydropower,wind power and photovoltaic,which will become an indispensable part of energy supply.In daily life,the ultra-low frequency environmental vibration caused by mechanical movement and physical activities is everywhere.The vibration energy can be converted into electrical energy to supply the load equipment through piezoelectric conversion and electromagnetic conversion.The widespread presence of ultra-low frequency vibration energy in the environment but often greatly wasted,this thesis proposes an ultra-low frequency broadband piezoelectric and electromagnetic hybrid vibration energy harvester based on the mechanical structure of string driven rotor,in order to achieve energy harvesting in a wide frequency band under ultra-low frequency vibration.The string driven rotor structure efficiently converts the vertical vibration into the kinetic energy of the suspended rotor in circular motion,realizes the frequency up-conversion,and converts the external vibration excitation into stable rotor rotation,and then coupling the piezoelectric cantilever and electromagnetic coil structure to generate voltage through the nonlinear effect of the magnet.At the same time,the interface circuit is designed by full bridge rectifier and DC-DC converter,which is used as the bridge between the output of energy harvester and the load or energy storage equipment.In this thesis,based on the basic theory of piezoelectric and electromagnetic energy harvesting and the basic principle of string driven rotor structure,the conversion structure and piezoelectric and electromagnetic hybrid energy harvesting mode of string driven rotor are determined by electric and mechanical analysis through simulation and test.Based on the design,3D modeling of the structure is carried out,and advanced manufacturing technologies such as 3D printing were used for processing.and combining other components to assemble two kinds of energy harvester prototypes,namely,the push-down type and the pull-down type.Meanwhile,the interface circuit was designed and made with the help of circuit design software and components.By building the experimental platform,the prototype and interface circuit are tested from the limit excitation frequency of continuous rotation,piezoelectric and electromagnetic output performance and circuit function.The experimental results show that energy harvester prototype has excellent ultra-low frequency vibration response and frequency upconvert ability and the performance of piezoelectric electromagnetic power output,with 1.14 m W piezoelectric maximum power output and0.4m W electromagnetic maximum power output.It can continuously respond to vibration below 2.3Hz,and respond to vibration with a minimum amplitude of 3mm,wideband energy harvesting at ultra-low frequencies is realized.The interface circuit can work normally under the input voltage as low as 340 m V,and has good combination with the energy collection device.