Handling Stability Analysis And Steering Trapezium Optimization Design Of An Electric Vehicle

In recent years,with the aggravation of environmental pollution and energy shortage,new energy vehicles,especially electric vehicles,have become a hot research direction in the automotive industry and have broad market prospects.Due to the difference of power system between electric vehicle and traditional automobile,there are differences in chassis layout and mass distribution between electric vehicle and traditional automobile.Therefore,it is necessary to re-analyze the handling stability of electric vehicles on the basis of the study of traditional vehicle handling stability.This subject takes an electric vehicle as a prototype,establishes the vehicle multi-body dynamics model and carries on the experimental verification.On this basis,two main aspects are studied: one is to optimize the steering trapezium structure in view of the problems of running deviation and tire wear during driving;the other is to improve vehicle handling stability,a multi-parameter optimization method of vehicle handling stability based on D-optimal test design was proposed.At present,the research on the handling stability of electric vehicles has become a important research topic,which has important theoretical significance and engineering value.It includes the following aspects:(1)The multi-body dynamics model of the vehicle was established and tested.Firstly,the coordinates of key points and other parameters needed for vehicle modeling are measured;then,based on the measured data,the multi-body dynamics model is established,including seven subsystems: front suspension subsystem,steering subsystem,body subsystem,rear suspension subsystem,tire subsystem,brake subsystem and power subsystem;finally,the constant radius cornering test and the slalom test are made by using the test vehicle.The test results are compared with the simulation results.The analysis results show that the test data and simulation data have the same trend of change,and the error is small,which verifies the accuracy of the multi-body dynamic model.(2)The vehicle handling stability was analyzed and evaluated.Based on the established the multi-body dynamic model,six tests of vehicle handling stability,including steady static circular test,cornering with steer release,steering portability test,steering wheel angle step input,steering wheel angle pulse input and slalom test,are carried out according to the vehicle handling stability test method.According to the limit value and evaluation method of vehicle handling and stability index,each test was scored and evaluated,and the single and total scoring values were obtained.The calculation results show that the original vehicle has poor steering returnability performance.(3)Steering trapezium optimization analysis based on response surface method.Aiming at the problems of running deviation and tire wear during driving,firstly,according to Ackerman principle,the design requirements of steering trapezoid are expounded,and the range of Ackerman error and toe angle in steering situation and parallel wheel travel is analyzed.Then,sensitivity analysis of key hard points of steering trapezoid was carried out,and the coordinate values with greater influence are selected to optimize them based on response surface method.After optimization,the maximum Ackerman error was reduced by 51.49%,and the range of toe angle was reduced by 40.44%,which alleviates the phenomena of running deviation and tire wear.Finally,the influence of steering trapezoidal optimization results on vehicle handling stability is analyzed.The analysis results show that steering trapezoidal optimization improves vehicle handling stability.(4)In order to improve vehicle handling stability,a multi-parameter optimization method for vehicle handling stability based on D-optimal test design was proposed.Firstly,the effects of steering wheel alignment parameters,suspension stiffness,tire lateral stiffness,centroid position and wheelbase on vehicle handling stability are analyzed.Then,the general evaluation score of handling stability was taken as objective function,and the design variables are centroid height,centroid position,wheelbase,spring stiffness,front tire lateral stiffness and rear tire lateral stiffness.Based on D-optimal test design,the response surface model between vehicle parameters and total evaluation score was fitted.Finally,the improved genetic algorithm was used to optimize vehicle handling stability.The results show that after optimization,the centroid height off the ground,spring stiffness and front tire lateral stiffness decrease to a great extent,while the rear tire lateral stiffness increases to a great extent,and the wheelbase hardly changes;among them,steering correction test scores increase by 20.43% and steady static circular test scores increase by 27.31%.The general evaluation score of vehicle handling stability increased by 8.98%.