Structural Design And Performance Analysis Of Electric Logistics Vehicle Frame

With the sustained and rapid development of the social economy,the urban logistics distribution system is also growing.With the advantages of pollution-free,high efficiency and strong support from national policies,electric logistics vehicles have become a new choice for medium and short distance transportation and urban logistics distribution.Major auto companies have seized the opportunity of electric new energy vehicles,and vigorously developed electric logistics vehicles.However,the electric logistics vehicles launched by many manufacturers are simply improved on the basis of the original light truck.There is no special frame structure design for the power system layout,the vehicle mass distribution,the working conditions and the light weight requirements of the electric logistics vehicle.In view of the above problems,this paper relies on the key research and development project of Shanxi Province-Research and development of key technologies of urban pure electric light trucks,conducts a forward design of electric logistics vehicle frame with the design goal of specialization and light weight.The main contents and main conclusions are as follows:Firstly,the experimental modal analysis of the original frame of an electric logistics vehicle was carried out,and the static and dynamic characteristics of the original frame were analyzed by using 3D modeling and finite element analysis.Compared with the modal test results,the reliability of the frame finiteelement model and the validity of the modeling method are verified.Then,the dynamics mathematical model of electric logistics vehicle is established,and the influence of different power system layout and vehicle mass distribution on the vertical dynamics performance of the vehicle are compared and analyzed.And the vibration characteristic of the driving motor is analyzed by real vehicle test.The analysis shows that,compared with the traditional driving type,the increase of the mass under the spring of the centralized driving electric logistics vehicle has a greater impact on the RMS of the rear wheel dynamic load,which directly affects the driving safety of the whole vehicle.It is finally determined that the electric logistics vehicle adopts the traditional driving form of power motor spring arrangement.In order to realize the special design of the frame structure,based on the analysis results of the static and dynamic characteristics of original frame and the overall layout characteristics of electric logistics vehicle,the multi-stiffness and high-frequency design objectives of the frame structure are proposed.The mathematical models of multi-stiffness topological optimization objective function and low-order natural vibration frequency topological optimization objective function are respectively defined by the compromise programming approach and the average frequency method.And using the compromise programming approach to define the multi-objective topology optimization mathematical model of comprehensive stiffness and natural frequency,and the frame topological structure which meets the requirements of stiffness and vibration frequency is obtained.Based on the frame topological structure,the new frame geometry model is established,and the static and dynamic characteristics of the frame are analyzed by finite element method.The results show that the new frame meets the operational requirements,and the static and dynamic performance is better than the original frame,with the total mass reduction by 7.4 %.In order to furtherrealize the lightweight of the frame,the size optimization design of the new frame is optimized based on the sensitivity analysis method under the premise of satisfying the vehicle performance.The final result shows that the weight of the lightweight frame is reduced by 11.2 %,and the structural performance still meets the requirements.This paper systematically studies the structural design and performance analysis of the electric logistics vehicle frame.It can effectively improve the stress distribution and natural vibration frequency,reduce the weight and improve the performance of the electric logistics vehicle frame,and provide a reference for the forward design of the electric logistics vehicle frame structure.