Research on Design of Variable Gear Ratio of Steer-by-Wire System and Comprehensive Feedback Control of Front Wheel Angle

In the research field of the handling and stability of steer-by-wire vehicles, the single scheme of feedforward control in the sense of steady state or dynamic feedback control is very conservative in controller design, which brings challenges to the improvement of vehicle handling stability. In this paper, the vehicle dynamics model including the steer-by-wire system is established in Simulink and Carsim. Taking the objective comprehensive evaluation index of vehicle handling stability as the optimization objective function, the optimal value of the steady-state gain of the steering wheel angle to the yaw rate as well as the variable gear ratio are obtained through the joint simulation experiment. Based on the obtained variable gear ratio, a comprehensive feedback control strategy for the front wheel angle is designed based on the combination of yaw rate sliding mode variable structure control and lateral acceleration PID control. Finally, the double-lane-change and the sinusoidal input driving scenario are selected for hardware-in-the-loop experiments to verify the effectiveness and real-time of the proposed control strategy. The experimental results show that the proposed variable gear ratio and comprehensive feedback control strategy can effectively improve the steering stability and safety of the steer-by-wire vehicle.