Performance Matching And Optimization Of Suspension And Steering System For In-wheel Motor Electric Car Chassis

With the extensive use of the traditional internal combustion engine vehicles, the dependence on non-renewable energy like petroleum and the environmental pollution is becoming more and more severe. Therefore, nowadays many countries are paying more attention on the development of new energy vehicle, especially for electric vehicle. Because the motor-in-wheel electric vehicle has many exclusive advantages, the research and development on motor-in-wheel electric vehicle has received great focus these years.This paper is based on the National 863 Project "New Designing Technology of Multi-Objective Performance Development for Electric Car Chassis", focused on "Performance Analysis and Optimization For the Steering and Suspension System of Motor-in-Wheel Electric Car". In this paper, a rigid-flexible coupling virtual prototype car model was built by using ADAMS/Car and finite element analysis (FEA) software according to a A-class sedan, which was served as a standard comparison car. In accordance with the vehicle riding comfort and handling stability road test method regulated by the national standard, driven control files (DCF) were edited in ADAMS/Car, which were used to control the prototype car model performing riding comfort and handling stability simulation analysis, including steady state cornering, steering wheel returnability, and steering handiness performance. The virtual prototype model for the standard comparison A-class car was validated through comparing those simulation analysis results and road test results. The model consists of front suspension subsystem, rear suspension subsystem, steering subsystem, power subsystem, braking system, tire subsystem, anti-roll bar subsystem and car-body subsystem model.Considering the arrangement of battery and in-wheel motor, changed the space structure of front suspension, rear suspension and steering system based on the comparison virtual prototype car chassis, and then established the motor-in-wheel electric car. Through performing wheel jumping and static steering simulations for the suspension and steering system, and analyzing the simulation results, the influence of the suspension and steering trapezoid structure hard-points for wheel alignment parameters and steering ability parameters changeability was studied. According to the analysis, choosed the suspension kingpin parameters and steering angle Ackerman error as design objectives for suspension and structure optimization. Then designed the DOE analysis with the Latin hypercube design method based on ADAMS/Insight, and made the impact sensitivity analysis to determine the design variables to be optimized. Through the redesign of simulation test, established response surface model (RSM) between the defined objectives and design variables, then used the optimization module provided by ADAMS/Insight to perform the multi-objective optimization, The suspension structure and steering trapezoid structure of motor-in-wheel electric car was determined by selecting the best calculated value for choosed design variables.Considering the riding comfort and handling stability of the electric car, choosed the body roll angle changes during steady-state simulation and weighted root mean square for vertical vibration acceleration of the driver seat during riding comfort simulation as the optimization objectives, matched the spring stiffness and damping coefficient of the front and rear suspension and determined their final values based on DOE analysis and ADAMS/Insight software. Finally, performed a series of simulation analysis for optimized virtual prototype electric car model. Compared with initial results, the analyzing result showed that the electric vehicle advanced a lot in performance after optimization.