| Facing with the growing serious problem of energy shortage and environmental pollution,the popularization of electric tractors has attracted wide attention and become one of the important methods to improve this problem.However,due to the small capacity and long charging time of electric tractor power battery pack,it can not meet the requirements of longterm continuous work.In the working process of electric tractor,the power battery pack is subjected to strong vibration shock when faced with the structure characteristics of nonsuspension system and wide range frequencies and large amplitudes of soil ground excitation.This creates favorable conditions for the capture and utilization of vibration energy.For this reason,a mechanical electromagnetic vibration energy regenerative decive based on the floating power battery pack is proposed.A dynamic model of vibration energy regenerative decive under harmonic excitation is established,and the effect of parameters on the energy recovery performance of the vibration energy is analyzed by numerical simulation and verified by bench tests.Based on excitation source model,the energy recovery performance of the vibration energy regenerative decive when applied to a wheeled small electric tractor is studied.Field tests are conducted to verify the effectiveness of the vibration energy regenerative decive applied to the electric tractor.It shows that the device can recover the vibration energy of the wheeled small electric tractor,and it can also effectively alleviate the vibration of the power battery pack.The main research contents and conclusions are as follows:(1)Structural design and simulation analysis of mechanical electromagnetic vibration energy regenerative decive.A mechanical electromagnetic vibration energy regenerative decive based on the floating power battery pack is proposed and its structure is designed.The structure and movement of the mechanical electromagnetic vibration energy regenerative decive are analyzed,and the analytical calculation method of the time-varying meshing stiffness of the rack and pinion transmission mechanism is verified.Based on the characteristics of the generator and the energy regenerative circuit and the gear transmission dynamics characteristics,the five-degree-of-freedom dynamic model of the vibration energy regenerative decive is established considering the reserve gap of the one-way clutch.Under the action of harmonic excitation,the energy recovery performance and damping characteristics of the vibration energy regenerative decive are analyzed by numerical solution.The results show that the damping force increases with the increase of the amplitude and frequency of harmonic excitation.However,with the increase of external load,the damping force of vibration energy regenerator decreases.The energy regeneration rate of vibratory energy regenerator increases with the increase of excitation amplitude and frequency.When the amplitude of the input displacement excitation is 0.03 m and the frequency is 4Hz,the maximum energy regeneration rate of the vibratory energy regenerator is 34.24%.(2)The bench test of mechanical electromagnetic vibration energy regenerative decive is carried out.The bench test is used to provide input displacement excitation for the vibration energy regenerative decive by setting different excitation frequencies and intensities.The performance of vibration energy regenerative decive is analyzed from two aspects of energy recovery performance and damping characteristics.The experimental results show that the ratio of vibration velocity amplitude between the lower box body and the power battery pack is greatly affected by the input excitation of the vibration energy regenerative decive.When the intensity of vibration energy regenerator is 40% and the frequency is 4Hz,the damping force of vibration energy regenerative decive is the largest,and the vibration reduction effect of the power battery pack is the best.Under the same excitation frequency,the greater the intensity(amplitude)of the input excitation,the greater the energy regeneration rate of the device.Under the same excitation intensity(amplitude)condition,the energy regeneration rate of the device increases with the increase of excitation frequency.When the external load resistance of the vibratory energy regenerative decive is 120Ω,the intensity of input displacement excitation is 40%(amplitude is 4.73mm),and the frequency is 4Hz,the maximum energy regeneration rate of the device is 26.32%.When the input excitation amplitude and frequency are the same,the energy regeneration rate of the vibratory energy regenerative decive increases with the increase of external load.The variation trend of bench test results is consistent with that of simulation analysis results,but the energy regeneration rate obtained from bench test is smaller than that of simulation analysis.The experimental results show that the structure design of the device is effective,and the accuracy of the dynamic model is verified.(3)Research on excitation source of vibration energy regenerative system applied to electric tractor.The dynamic contact characteristics of soil surface and tire were studied.The model characterization of the front wheel of the wheeled small electric tractor was carried out,and the rim-tread dynamic model was established;in order to obtain the deformation amount of the soil and the ground under the action of the front wheel,the force and strain of the soil and the ground in the elastic and plastic deformation stages were studied respectively relationship.The time domain curve of displacement excitation is used to simulate the roughness of soil surface.The simulation data show that the tire settlement includes the deformation of the tire itself and the elasto-plastic deformation of the soil surface,which decreases with the increase of tire pressure.However,the elasto-plastic deformation of soil surface increases with the increase of soil surface roughness,that is,the increase of input displacement excitation amplitude.(4)Research on Energy Recovery Performance of Vibration Energy Regenerative System of Wheeled Small Electric Tractor.By harmonic superposition method fitting soil ground of time domain is derived displacement curve,dynamic model which is based on above,set up the electric tractor vibration feeder can complete mathematical model of the system,and then use numerical method to obtain the system dynamics simulation results,the root mean square value of frame and power battery under vertical vibration displacement were characterized,The damping characteristics of vibration energy regenerative system are further evaluated.The simulation results show that the damping characteristics of the vibration energy regenerative system are better under the excitation of class C and class D road.Compared with the vertical vibration displacement of the lower box,the vertical vibration displacement of the power battery pack is improved by 8.04% at the maximum.Under the condition of the same road level,the faster the speed of the wheeled small electric tractor,the greater the energy regeneration rate of the system.Under the same speed condition,the worse the road condition is,the higher the energy regeneration rate of the system is.(5)The field test of vibration energy regenerative system of electric tractor is carried out.The installation position of the mechanical electromagnetic vibration energy regenerative decive on the wheeled small electric tractor is determined by the test.Field test is carried out by changing the speed of electric tractor and external load.According to the field test data,under the condition that the soil surface roughness is basically the same,the electric energy regeneration rate of electric tractor vibration energy regenerative system increases with the increase of external load and the increase of tractor speed.The research shows that the application of vibration energy regenerative decive in wheeled small electric tractor is effective and the effect of vibration energy recovery is obvious. |
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