Research on Variable Steering Ratio Control Strategy of Steer-by-Wire System

In this paper, the variable steering ratio control strategies under normal driving conditions and emergency driving conditions were proposed. The variable steering ratio control under normal driving conditions is based on variable yaw rate gain, and takes into account the driver’s operating habits and vehicle handling stability. The steering ratio varies with the vehicle speed and the steering wheel angle, which ensures the vehicle steering sensitivity at low speed and the steering stability at high speed. The variable steering ratio control under the emergency driving conditions is based on yaw rate dynamic feedback control, and the steering ratio varies with the vehicle movement status. We use active steering control which is based on active disturbance rejection control to achieve yaw rate dynamic feedback control, which can improve vehicle stability without affecting the longitudinal movement of vehicle. In order to verify the effectiveness of the proposed variable ratio control strategy, using CarSim and Simulink to simulate the typical driving conditions, the simulation results show that the variable steering ratio control can effectively reduce driver’s driving burden, and improve the response characteristics of the vehicle and the vehicle’s steering stability and active safety.