Vertical Performance Analysis And Optimization Of Distributed Electric Vehicle Under Typical Conditions

With the emphasis on environmental pollution and energy consumption,electric vehicles have become one of the important development trends of vehicle industry.In recent years,the distributed electric vehicle driven by hub motor has become a hot research topic due to its advantages of high energy space utilization and high controllable degree of freedom.Both traditional vehicles and electric vehicles are oriented by the key requirements of technological development,that is,to ensure that the performance of vehicles meet the technical and safety standards.However,the installation of hub motor will not only lead to the increase of unsprung mass,but also produce negative effect of electromagnetic excitation,both of which will lead to the negative impact on the vertical performance of the whole vehicle system,and there are also hidden dangers in driving safety.Most of the existing studies are aimed at one of its shortcomings,so it is necessary to introduce a comprehensive analysis of the impact of hub motor on the vertical performance of electric vehicles,which is of great significance for the follow-up in-depth research and design optimization.The main contents of this paper are as follows:Without considering the electromagnetic excitation,the influence of unsprung mass increase on the vertical performance of electric vehicle under typical working conditions is explored separately.The basic parameters of the whole vehicle in line with the dynamic index are drawn up,and the motor and battery selection and parameter matching are completed.The vertical vibration model of a single wheel is built to analyze the vertical vibration response of the distributed electric vehicle driven by hub motor under the conditions of the increase of unsprung mass,different vehicle speeds and different road grades.It is concluded that the introduction of hub motor has obvious adverse effects on the dynamic load and vertical vibration acceleration of the wheel,but has little effect on the dynamic deflection of the suspension.A seven degree of freedom vertical vibration model of the whole vehicle is built,and the time-domain response curves of the existing motor mass,0.9 times of the motor mass and 0.8 times of the motor mass are compared.It is concluded that the lightweight design of the electric vehicle wheel with hub motor in the wheel is one of the schemes to optimize the performance of the electric vehicle.Then,the principle of unbalanced electromagnetic force is analyzed.Based on the seven degree of freedom model of the whole vehicle,considering the existence of motor bearing stiffness,the 11 degree of freedom vertical vibration model of the whole vehicle is established,and the influence of road excitation and unbalanced electromagnetic force on the vertical dynamics of the vehicle is studied.The results show that the unbalanced electromagnetic force,as the internal force of the hub motor,will lead to the aggravation of the eccentricity of the stator and rotor of the hub motor,and will lead to the resonance phenomenon of the vehicle at a low speed,which will further deteriorate the ride comfort and safety performance of the electric vehicle.Finally,in order to improve the influence of hub motor on the vertical performance of distributed electric vehicle under typical working conditions,the suspension optimization model is established.The minimum sum of the root mean square values of body vertical vibration acceleration,wheel dynamic load and motor vertical vibration acceleration is taken as the optimization objective,and the maximum vertical displacement of motor is taken as the constraint condition,After optimization,all the indexes are obviously improved,and the vertical performance of the hub motor-driven distributed electric vehicle is improved.