Study On The Electromagnetic Vibration Energy Harvester Based On Diamagnetically Stabilized Levitation

With the rapid development of wireless sensor networks,portable electronics,and wearable devices,one unavoidable problem is that uninterrupted energy supply to these applications is still not solved,which seriously hinders them from developing their own potential.Currently,conventional electrochemical batteries are the main power sources.However,electrochemical batteries have the disadvantages of a short lifespan,low energy storage,and require periodic charging or regular replacement.In addition,disposal of the expired batteries may cause environmental pollutions.For large-scale wireless sensor networks,the number of wireless sensor nodes is large and widely distributed,it is unrealistic to periodically replace batteries or charge batteries.Vibration energy harvester can covert the ambient vibration into electrical energy,which is expected to realize long-term and stable power supply for electronic devices and has received extensive attention.The dissertation mainly focuses on the electromagnetic vibration energy harvester based diamagnetically stabilized levitation.A new structure of vibration energy harvester has been present in this work,which has a wide operating bandwidth and can harvest vibration energy in multi-directions.Two different dynamic models were built according to the different directions of excitations,and the vibration characteristics of the two models were analyzed.The static levitation characteristics of the diamagnetically stabilized levitation structure were studied.The output characteristic of the vibration energy harvester was analyzed.The experimental prototype of the proposed vibration energy harvester was fabricated and tested on a vibration exciter.The practicality of vibration energy harvester was verified.The main work and the conclusion of the dissertation are in the following:1.To harvest multi-directions vibration energy and widen the operating bandwidth,an electromagnetic vibration energy harvester based on diamagnetically stabilized levitation was proposed,which is mainly composed of diamagnetically stabilized levitation structure,induction coils,and elastic films.A second-order“spring-mass-damping”dynamic model was established for the vertical excitation,and a piecewise linear vibration model was established for the horizontal excitation,and the vibration characteristics of the two models were analyzed,the calculation method of the induced voltage is introduced,and the superiority of nonlinear vibration energy harvester is discussed.2.A method of COMSOL with MATLAB Co-simulation technology is proposed for computing the weak magnetic force and diamagnetic force,the static levitation characteristics of the diamagnetically stabilized levitation structure are studied by simulation and experiment.It is found that the diamagnetically stabilized levitation has monostable,bistable and asymmetrical monostable.The monostable maximum active space and the bistable maximum active space of the floating magnet were analyzed by Taguchi method,and the analysis results showed that the parameters of the floating magnet and the thickness of the pyrolytic graphite plate are the important factor affecting the maximum activity space.3.The structure parameters of the harvester were selected,and the diamagnetically stabilized levitation structure with monostable was determined as the main structure of the vibration energy harvester.The motion state of the floating magnet and the response of the harvester were studied by the Rung-Kutta method.The damping of the floating magnet was measured,and the stability of the voltage solution was analyzed,the influence of the component parameters on the output performance of vibration energy harvester under horizontal vibration is analyzed.4.The experimental prototype of the harvester was fabricated,and the device for testing the stiffness of the elastic film was designed,and the experimental test platform was built.The performance of the proposed vibration energy harvester was measured,and the feasibility of the harvester was verified.When the excitation acceleration in the vertical direction is 0.04m/s~2,the maximum voltage of the harvester is 21.8 mV,and the operating bandwidth is 0.4 Hz.When the horizontal excitation amplitude is 5mm,the operating bandwidth of harvester can reach to 3.2Hz,the maximum output voltage is 78 mV and the maximum output power is 56.3?W.When the horizontal excitation acceleration is 3 m/s~2,the operating bandwidth is 2 Hz,the output power is 18?W,and the maximum output voltage is 44 mV.