Study Of Diamagnetic Levitation Electromagnetic-Piezoelectric Hybrid Energy Harvester

With the development of electronic technology,low-power wireless sensor networks are widely used in industry and daily life.Wireless sensor networks,in which a large number of wireless sensor nodes are arranged and distributed widely,needs to face the problems caused by the short lifespan,regular replacement and environmental pollution of traditional batteries.Energy harvesters,which generate electrical energy by harvesting energy from the environment,have replaced traditional batteries and received widespread attention.To address the problems of small operating bandwidth,high amplitude requirement of vibration source and single collection direction of general vibration energy harvesters,this thesis proposes an electromagnetic piezoelectric composite energy harvester based on antimagnetic levitation.In this thesis,a new structure of electromagnetic piezoelectric hybrid energy harvester is proposed firstly.The equivalence current method is used to obtain the analytic equation of the magnetic field containing the generalized complete elliptic integral,the coordinate system transformation method is applied to the calculation of the magnetic force between non-coaxial cylindrical magnets.The computational accuracy of the obtained magnetic force solution model is similar to that of COMSOL,and the computational speed is increased by more than 100 times.The diamagnetic force solution formula is derived and corrected by simulation and experiment,the introduced diamagnetic force correction factor is 1.73.The theoretical formula for the damping force solution is given.Combining the equations for magnetic force and antimagnetic force,the static model of the collector is established.The three stable levitation states of the floating magnet are analyzed.The test platform is built to verify the static model.And the errors of the obtained levitation heights are all less than 5%,the errors of the maximum levitation gap are all less than 10%.The effect of different structural parameters on the monostable maximum activity space is analyzed using Taguchi method and the structure is optimized.Then the power generation models of the coil and the piezoelectric sheet are constructed separately.The segmented nonlinear equations and the duffing equations are analyzed according to whether the floating magnet collides with the piezoelectric structure in the vibration process.The nonlinear amplitude-frequency characteristic curves are obtained by using the multi-scale method to analyze the duffing equations.The dynamic theoretical model of the harvester is constructed.The output voltage in the coil is analyzed given the structural parameters.Finally,the stiffness of the PVDF and PZT piezoelectric structures used in the experiment are tested separately using a pressure tester,and then the vibration excitation experiments are completed.Comparing the electromagnetic generation results of the dynamic model with the experimental results,the model and the experimental results are in general agreement.When the frequency ratio is 0.6～0.8,the jumping phenomenon occurs.The experimental results show that the effective bandwidth of the electromagnetic power generation structure is over 8.5 Hz.When the excitation frequency is 2.6 Hz and the excitation amplitude is 4 mm,the single-side coil voltage RMS value reaches 250.69 mV and the power is 86.6 μW.After connecting to the twelve times rectifier circuit,the LED light can be lit after about 10 seconds of charging.When the excitation frequency is 3.2 Hz and the excitation amplitude is 8mm,the peak voltage obtained by accessing the PZT disk piezoelectric sheet can reach 10 V and the peak value of PVDF film can reach 2 V.