Research On Double Rectangular Spiral Piezoelectric Energy Harvester With Multiple Degrees Of Freedom

With the development of science and technology,human society’s demand for energy is increasing day by day,and the environmental pollution caused by energy shortage and energy use has become a difficult problem that people have to face.Therefore,the utilization of green and clean energy begins to be concerned by countries all over the world,among which the green energy is widely used,such as solar energy,wind energy,tidal energy and wave energy.Mechanical vibration is a common physical phenomenon in nature and daily life,such as the vibration of the road surface where cars are running,the vibration of railway tracks when trains and subways are running,and the weak vibration of buildings along the road.As a form of green energy,mechanical vibration energy has a high energy density,and its potential energy value has attracted the attention of researchers.In order to collect and utilize low frequency vibration energy and realize electromechanical energy conversion in a wide frequency range,a piezoelectric energy harvester with double rectangular spiral structure is designed in this paper.The energy harvester has a low mode frequency,and the mode frequency distribution is concentrated in the low frequency range,which can realize the effect of wide frequency power generation.Firstly,the power generation performance of a double-rectangular spiral multi-degree-of-freedom piezoelectric energy harvester is studied by theoretical analysis and finite element simulation.The electromechanical coupling model of the piezoelectric cantilever beam and the vibration model of the piezoelectric energy harvester system were established,and the modal simulation was carried out to analyze the first five modes of the piezoelectric energy harvester and verify the rationality of the theoretical results.By using finite element simulation software,the piezoelectric energy harvester with double rectangular spiral shape and multiple degrees of freedom,T-beam piezoelectric energy harvester and single cantilever beam piezoelectric energy harvester were simulated respectively.The influences of length and width of piezoelectric beam,thickness of metal substrate,thickness of piezoelectric ceramic plate,thickness of metal block and number of piezoelectric beams on the power generation performance of three kinds of piezoelectric energy harvester were investigated.Three kinds of piezoelectric energy harvesters with higher open-circuit voltage are determined,and the modal simulation of the three kinds of piezoelectric energy harvesters with these structural parameters is carried out,and the modal frequency and mode shape of each order are analyzed.Secondly,the power generation effect of the double rectangular spiral piezoelectric energy harvester with multiple degrees of freedom is verified by experiments.Built experimental platform,according to the simulation of the structural parameters of piezoelectric prisoner made a double rectangular spiral can,T beam ere piezoelectric energy absorber and single cantilever piezoelectric prisoner can implement the experimental prototype.The power generation performance of three kinds of piezoelectric energy harvesters was tested under the excitation intensity of 2g,and the open-circuit voltage of each piezoelectric plate of each piezoelectric energy harvester at different frequencies was studied.Two kinds of standard energy extraction circuits were made in parallel and in series,and the output performance of the piezoelectric energy harvesters in parallel and in parallel were studied.The best matched impedance of the three kinds of energy harvesters was studied under different loads with different access resistance values,and the relationship between the output voltage,output power and vibration frequency of the three kinds of piezoelectric energy harvesters was analyzed.The experimental results show that the maximum output power of the double-rectangular spiral multi-degree of freedom piezoelectric energy harvester is8.01 m W under the excitation intensity of 2g.The maximum output power of T-beam piezoelectric energy harvester is 0.15 m W;The maximum output power of single cantilever piezoelectric energy harvester is 0.053 m W.The mode frequency distribution of the double-rectangular spiral multi-degree of freedom piezoelectric energy harvester is concentrated.The optimal working frequency band is 4-18 Hz,and the peak output power in this frequency band is all greater than 4m W.The frequency band with output power greater than 0.1m W covers 33.6% of the above working frequency band.The mode frequency distribution of the T-beam piezoelectric energy harvester is relatively dispersed,and it has certain wide-band power generation capacity,but the power generation effect is far less than that of the double-rectangular spiral multi-freedom piezoelectric energy harvester.Single cantilever piezoelectric energy harvester has only one mode frequency in the low frequency range,and the output power is low,so it is not suitable for broadband power generation.