Research On Integrated Optimization Method Of Chassis System For Electric Wheel Vehicle

The electric wheel vehicle has become the future development trend with the feature of energy saving,environmental protection and simple arrangement.Steering system,suspension system and braking system are the three important chassis subsystems of electric vehicle.Because of the coupling relationship of these three subsystems,while the performance of a subsystem is improved,it must have a certain impact on other systems.The performance of the subsystem is simply superimposed and optimized,and the optimal comprehensive performance can not be obtained.Therefore,it is necessary to rely on the integrated optimization of the three systems for achieving the optimal comprehensive performance.This paper makes a comprehensive study on the structural features of electric wheel vehicle's wheel hub motor,considering the integration and coupling relationship of differential steering system,active suspension system and differential braking system.the dynamic model of electric wheel vehicle chassis system is established,including the four degrees freedom model of whole vehicle,dynamic model of differential steering system,dynamic model of active suspension system,dynamic model of differential braking system,wheel model and road input model.Based on MATLAB and CARSIM,the established chassis system model is validated to ensure the correctness of performance index and optimization results.Based on the driver ride comfort,the performance index of each chassis subsystem is put forward and the quantitative processing is carried out.Through the performance analysis,the sub subject function which has great influence on the driver ride comfort is determined.Through the analysis of the parameters,the structural parameters which have great influence on the objective function of the sub discipline are obtained,and this is used as the optimization design variable of the sub discipline.Considering the requirements of the motion interference and the subsystem structure of the three subsystems,the constraint conditions of the subsystems and the chassis system are obtained by the constraint analysis.Based on the TOPSIS method,the driver ride comfort is reconstructed and the weight coefficient of each sub objective in driver ride comfort is studied to solve the subjectivity problem in the weight selection.On the basis of CO method,the hybrid hierarchical cooperative optimization method is designed.The driver ride comfort is taken as the total system target,and the steering road feel,braking feeling and suspension ride comfort are taken as the sub-disciplinary targets.The structural parameters that affect the performance of the steering system,braking system and the suspension system are choosen as the design variables.The constraint conditions are determined by subdisciplinary analysis,which include steering sensitivity,lateral acceleration,braking deceleration,relative damping coefficient,relative dynamic load of wheel and ground,dynamic deflection and so on.The coupling analysis layer is establed by the coupling relationship between subsubjects.The chassis system is systematically decomposed and the integrated optimization model of the chassis system is established.Based on the combination of MATLAB and ISIGHT,an integrated optimization framework for the electric wheel vehicle chassis system is constructed.The integrated optimization design of electric wheel vehicle chassis system is carried out by using NSGA-II algorithm.Through the research on the above problems,it can provide theoretical basis and optimization method for integrated optimization design of electric wheel vehicle chassis system.