| In order to meet the self-powered demand of wireless sensing nodes,a variable-section bending beam piezoelectric vibration energy capturer is proposed for the shortcomings of current piezoelectric energy harvesters,such as high resonance frequency,narrow acquisition band,single acquisition direction,low power generation efficiency,low output voltage and low power,etc.It obviously appears multiple output wave peaks in the collection range of low frequency band,widens the working frequency band of the energy captor,and the output voltage amplitude is larger to improve the energy collection efficiency of the energy captor for irregular low frequency and wide frequency vibration.Further,the non-linear magnetic force is introduced by setting the spring and magnet to further increase the voltage amplitude and the acquisition band width,and the magnetic excitation of the magnet and spring makes the proposed variable cross-section bending beam piezoelectric energy acquisition device realize the three-dimensional all-round vibration energy acquisition.The proposed magnetically-excited variable-section bending beam piezoelectric energy harvesting device is validated by fabricating a captive energy array structure and designing a power supply application test.Firstly,this paper verifies the power generation performance and vibration characteristics of the beam by theoretical analysis of the variable-section bending beam structure and reasonable simplification of the complex mechanical model using the method of establishing multiple reference coordinate systems,and investigates its wide-frequency characteristics through modal analysis,and concludes that the bending beam has a larger number of characteristic frequencies in the low-frequency range,thus facilitating the wide-frequency energy harvesting in the low-frequency range of vibration energy.Secondly,in order to investigate the power generation performance of the variable cross-section bending beam structure,the finite element model is established to optimize the structural dimensional parameters,and the simulation analysis is carried out to find that the variable cross-section bending beam piezoelectric oscillator stress distribution is more uniform,which makes the piezoelectric material utilization higher,and the variable cross-section trapezoid with special bending structure makes the maximum output voltage higher and the resonant frequency lower,with three voltage peaks at 11 Hz,24 Hz,and 51 Hz.three voltage peaks at 11 Hz,24 Hz and 51 Hz.The power generation performance of different beam sizes is investigated,the structural parameters are optimized,and the simulation results are experimentally verified.Then,in order to further optimize the power generation efficiency of the piezoelectric energy harvester,the nonlinear magnetic force is introduced on the basis of the variable cross-section bending beam to further make the area near the peak as wide as possible based on the original multiple peaks,thus maximizing the harvesting band of the energy trap in the low frequency range.In addition,the introduction of magnetic excitation is most important to achieve multiple directions of acquisition,greatly improving the energy acquisition efficiency and power generation performance of the capturer in complex vibration environments.The effects of the number of magnets,magnet polarity,magnet spacing,end beam bending angle,substrate thickness,and end beam length on the power generation performance of the energy capturer are experimentally investigated to further optimize the parameters of the monolithic energy capturing structure to obtain the best power generation effect.Finally,according to the optimized magnetic excitation variable section bending beam structure settings to produce the best capturer array,which selected two different thickness of the beam structure,the use of resonance band inconsistency,so that the array structure resonance band complementary to further broaden the capturer acquisition band,and finally achieve the full coverage of the effective acquisition band below 80 Hz.Finally,the power supply of the captive array is tested,and the experiments show that the designed captive energy can achieve high efficiency in all three axes,and the maximum instantaneous output power can reach 12.3 m W when the external load resistance is 20 KΩ.The experiments show that the magnetically excited variable cross-section piezoelectric capturer designed in this paper can meet the demand for auxiliary power supply for wireless sensing nodes.Fig.[87] Table [10] Reference [91]... |
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