Four-Wheel-Independent Steering Mechanism Design In 4WD In-Wheel-Motor Drive Vehicle

Four-wheel steering mechanism for automobiles has the functions of reducing turning radius at low speed and improving steering stability at high speed.As the steering technology with the highest technology content and the greatest improvement of vehicle flexibility,the four-wheel independent steering technology can easily realize the all-direction movement of the vehicle.However,because the four-wheel independent steering needs to control the movement of each wheel separately,the complexity of vehicle suspension system and steering system is undoubtedly increased.The structure of the vehicle is simplified to a certain extent and the arrangement of the four-wheel independent steering mechanism becomes more flexible because of the non-transmission shaft and half-axle of the vehicle driven by in-wheel motor.The purpose of this paper is to design a new four-wheel independent steering mechanism which can realize the functions of s small radius steering,turning around in situ,lateral driving and oblique driving of electric vehicles.The research contents are divided into the following five parts1.By analyzing the characteristics of in-wheel motor drive and the structure of four-wheel steering mechanism,a four-wheel independent steering mechanism for four-wheel in-wheel motor drive electric vehicle is proposed.Aiming at the optimization of steering power consumption,the parameters of four-wheel steering mechanism are determined by using the optimization toolbox of MATLAB,and the parameters are verified by ADAMS software.2.Establishment and validation of steering mechanism model.Firstly,the steering mechanism model of a single wheel is established by using CATIA software,and the simulation of the single wheel steering mechanism model is validated by combining ADAMS software.Then,based on the single wheel steering model,the steering mechanism model of the vehicle is established and simulated.In order to improve the reliability of the vehicle,emergency steering device is added to the front axle of the vehicle when establishing the steering mechanism model.3.Establishment and validation of a two-degree-of-freedom vehicle steering kinematics model.Firstly,the mathematical model of vehicle steering control is established based on Ackerman steering theory.Then,the simulation model of four-wheel independent steering is built with SIMULINK software.Finally,the control model is validated by simulation.4.Based on the steering mechanism model of the whole vehicle,the virtual prototype model of the whole vehicle is established by using ADAMS software.The steering performance of the vehicle with four-wheel independent steering mechanism designed in this paper is validated by using the established SIMULINK control model and virtual prototype model.5.Simulation and verification of steering mechanism under specific working conditions.Verify whether the vehicle with the four-wheel independent steering mechanism designed in this paper can realize the functions of small radius steering,turning around in situ,lateral driving and oblique driving.