Research On Design And Control Of Steering Mechanism Of Wheel Side Integrated System

In-wheel drive electric vehicles(IWD-Evs)directly install the powertrain in the wheel or wheel space,and form an in-wheel integrated chassis(IWIC)system with chassis subsystems such as steering and suspension,the system has unique advantages in terms of vehicle dynamics performance,economy,safety,and multi-mode driving function.As the wheel side steering mechanism is an important part of the in-wheel integrated chassis system,the working quality of the wheel side steering mechanism is directly related to the handling performance of the vehicle.Therefore,the design and research of the wheel side steering mechanism is of great significance.However,for in-wheel drive electric vehicles,there is a contradiction between the new steering function requirements and the maintenance of the basic performance of the vehicle.Aiming at the problems in the structure of the in-wheel integrated chassis steering system,this paper conducts related work such as wheel side steering mechanism assembly design,modeling,performance analysis and steering angle control research.The specific research content of this paper is as follows:First,analyze the design elements of the IWD-EV suspension steering system and the typical structure of the current steering scheme,and propose a new configuration of double main pin differential independent steering that can match the shaped multi-bar suspension to improve the contradiction between the requirements of steering function and maintain the basic performance of the vehicle,so that the vehicle has multiple steering modes such as lateral driving and in-situ steering;at the same time,the new integrated structure meets the requirements of the vehicle suspension steering system to have good geometric and kinematic characteristics and requirements for power transmission characteristics.Secondly,the overall structure design of the new wheel side steering mechanism is carried out,the in-situ steering torque is calculated according to the actual application scenarios,and the structural parameters of the steering motor,reducer,rack and pinion steering gear in the steering execution part are designed to complete the selection;In the transmission part,the worm gear reduction mechanism and other key structures are calculated and selected;then the prototype structure is designed in the three-dimensional CAD software according to the designed and selected parts;at the same time,the load is calculated and the restraint force is analyzed for typical working conditions,and the strength verification and deformation simulation of the designed key components are carried out in the finite element check module Workbench.After the above design process iteratively iterates the structure design and strength analysis process,optimizes the design,and finally obtains a new suspension steering system design scheme that meets the requirements of use.Then,based on Adams/Car,the hard-point design of the new wheel-side steering mechanism is carried out,the new suspension steering system model is built,and its structural principle is verified;at the same time,the wheel-side integrated structure loaded with the new suspension steering mechanism is checked for motion interference,it has been verified that the new suspension steering system configuration scheme can meet the demand for high maneuverability.And apply the newly built complete structure model to carry out the dynamic simulation test,examine the additional toe change produced by the universal joint on the drive shaft,and compare the wheel and vertical load changes of the conventional inward steering and the large steering angle mode.Finally,examine the fluctuation of the steering transmission ratio in the large-angle mode,evaluate and analyze the pros and cons of this new structural scheme.Finally,this paper studies the vehicle steering stability control of independent steering vehicles.The front wheel Ackerman angle relationship is considered in the control model,a more accurate vehicle model is used to design the upper vehicle yaw stability controller based on the nonlinear three-step method,and a bridge is established between the advanced model-based control method and actual engineering practice.And set up a control model on the Simulink platform to perform steering simulation analysis,verifying the effectiveness of the three-step nonlinear algorithm,realizing active Ackerman steering geometry control.It has reference significance for the follow-up steering control research.