Performance Investigation And Experiment Of Piezoelectric Mechanical-electromagnetic Compound Vibration Energy Regenerative System For Electric Tractor

As the key equipment in the field of new energy agricultural machinery development,currently there are mainly problems such as lack of electric energy and short range.Vibration energy recovery and utilization is an essential way to extend the travel distances of electric tractors.Therefore,this paper proposed a piezoelectric-mechanical-electromagnetic compound vibration energy recovery device based on floating battery pack and structural characteristics of a small wheeled electric tractor as a research platform.The device coupled two energy conversion methods to realize the efficient capture of vibration energy and its electrical energy conversion,while attenuating the shock and vibration of the battery pack,thus improving the security of the battery pack.Focusing on the nonlinear dynamic characteristics and energy recovery performance of the compound vibration energy regenerative device,the following research work was carried out in this paper.(1)The design and piezoelectric structure parameters of the piezoelectric-mechanical-electromagnetic compound vibration energy regeneration device are determined.Taking a small wheeled electric tractor as the research platform,considering the excitation source characteristics and the structure forms of the electric tractor without suspension,a novel piezoelectric-mechanical electromagnetic compound vibration energy regeneration device is proposed and designed,and the components and working principle of the energy feeder are introduced in detail.Then,based on the analysis results of the motion characteristics and force state of the energy regenerative device,the overall structural dimensions of the piezoelectric energy regenerative device and the stiffness of the system shock-absorbing spring are reasonably designed.And the parameters such as the length of the piezoelectric substrate,the thickness of the piezoelectric ceramic and the lever ratio are determined.(2)The energy dynamic characteristics study and performance test of piezoelectric-mechanical-electromagnetic compound vibration energy regeneration device.Considering the contact characteristics of gear meshing pairs and the force-electromagnetic-mechanical dynamic coupling interaction of the system,the 10 degree-of-freedom(DOF)nonlinear dynamic model of the system containing the time-varying meshing stiffness,electromechanical coupling factor,nonlinear gear backlash,comprehensive transmission error and damping was established.And its energy nonlinear dynamic characteristics were revealed numerically through the global bifurcation,phase orbit,Poincarémap and FFT spectrum.The results showed that the energy output response of the system presented a high-energy period-2 state within the ranges of the excitation frequency f∈[2.475,2.850Hz]and amplitude A_m∈[0.00644,0.01000m].Finally,the reliability of the established dynamic model was verified through comparative analysis between the prototype experimental and theoretical results,and it was shown that the prototype generated a maximum output voltage of 38V and a peak power of 14.44w at a load resistance of 100Ωunder the excitation frequency of 2.42Hz and amplitude of 0.002m.(3)The analysis of nonlinear dynamics behavior of compound vibration energy regeneration device based on POD dimensionality reduction method.For the purpose of reducing computational time and resources,the original dynamic model was reduced to a 3DOF model through the nonlinear transient proper orthogonal decomposition(POD)method and the proper orthogonal mode(POM)energy method.And the comparative analysis of bifurcation diagrams and relative error curves shows that the reduced model retains the complete dynamic characteristics of the original system.Then,the effect rule of electromechanical coupling factor,meshing stiffness fluctuation coefficient,damping ratio and dimensionless gear backlash on the bifurcation characteristics of the system vibration displacement of was analyzed based on the reduced model.The results showed that the system presented diverse dynamic behaviors including periodic,multi-periodic and chaotic motions under the excitation of multiple structural and mechanical parameters.Eventually,the stabilization and chaos intervals of the parameters are obtained,which can provide the technical support and theoretical basis for the dynamic design and control of the system.(4)The design and testing of the electric energy extraction circuit for a compound vibration energy regeneration device.According to the energy output response characteristics of the compound vibration energy regeneration device,an electric power extraction circuit including rectifier filter,LM317 voltage stabilizer and Boost-type DC-DC boost modules was designed.By analyzing the charging power matching rule of lithium battery pack of the electric tractor,the rectifier filter,voltage regulator circuit and lithium battery pack charging circuit were simulated and analyzed respectively in Multisim.Finally,the hardware system of the electric power extraction circuit was built and the vibration bench test was carried out to study the working performance of the whole power extraction circuit.(5)The piezoelectric-mechanical electromagnetic compound vibration energy regeneration system live vehicle test.In order to attenuate the shock and vibration of the power battery pack to ensure its security,the developed piezoelectric-mechanical electromagnetic compound vibration energy regeneration device was installed between the chassis of the small electric tractor and the lithium battery pack.And the electric power extraction circuit was connected with output side of the compound vibration energy regeneration device.Finally,an actual vehicle test of the compound vibration energy regeneration system was conducted.The results of the actual vehicle test show that after the electric tractor travels on the field grass for0.55h,the electric energy recovered by the compound vibration energy regenerative system can make the 16V/500F super capacitor fully charged.The equivalent theoretical calculation shows that the electric energy recovered by the compound vibration regenerative system can extend the endurance of the small wheeled electric tractor by about 0.747h after 4.183h of continuous vibration,which can increase its endurance by 17.86%.After plowing test 0.783h,the electric energy recovered by the system can make the super capacitor fully charged.The equivalent calculation shows that after 2.071h of plowing operation,the electric energy recovered by the compound vibration energy regenerative system can extend the plowing operation time of the small wheeled electric tractor by 0.269h which increases its plowing endurance by 13.01%.