Research On Road-feeling Design And Stability Control Of Steer-by-Wire System

In order to improve the vehicle handling performance and stability, the steer-by-wire(SBW)steering system has been paid more and more attention recently. Besides the function of power assist steering, SBW is able to realize the variable steering ratio and vehicle stability control by the analysis of ECU based on the input of the drivers.The SBW system can solved the problem of force and displacement coupled existed in traditional steering system with no mechanical link existing between the steering wheel and the road wheels.First of all, based on the co-simulation platform of Matlab/Simulink and CarSim, the SBW steering system dynamic model, nonlinear 2-DOF vehicle model, tire model, vehicle model and interference model are established Secondly, the source and kinds of road-feeling are analyzed. Considering the ideal variable steering ratio, a mixture road-feeling strategy is designed. Based on the H? robust control theory, the hand wheel torque control strategy is built to make the hand wheel torque under the reference of sensor noise, which is able to provide ideal road feel for driver. Then an extended Kalman filter is designed to estimate the vehicle motional state of the yaw rate and the sideslip angle.Based on the estimation, a control strategy for the vehicle stability under the interference condition is proposed. The LQG/LTR controller is built with the aim of tracking the target values of yaw rate and side slip angle.In the end, a test platform of SBW system is designed. The simulation and experiment results show that the controller proposed not only improves the vehicle handling performance and stability,but also offers a good road feel.