Design of variable ratio mathematical model for steer-by-wire system
by Ju Zhang; Xueyun Li; Jun Li
International Journal of Vehicle Performance (IJVP), Vol. 8, No. 4, 2022

Abstract: In order to ensure the vehicle safety, improve the steering handling stability of vehicles on low adhesion road and at high speed, a variable transmission ratio mathematical model of steer-by-wire (SBW) system is proposed considering vehicle speed and road adhesion coefficient comprehensively. A characteristic simulation experiment is performed to obtain the yaw rate gain of the vehicle based on the vehicle model in CarSim. Then, the correction function of the ideal yaw rate gain is built based on the error variation rule between yaw rate gain and the ideal yaw rate gain. And then the curve of variable steering ratio is designed and modified. The influence of road adhesion coefficient on transmission ratio is analysed, and the function relationship between road adhesion coefficient, vehicle speed, and transmission ratio is built. Finally, the vehicle trajectory tracking simulation model is built in CarSim and MATLAB/Simulink to validate the effectiveness of the designed variable steering ratio function. The results show that the designed steering ratio function could calculate the reasonable steering ratio of the SBW system according to different vehicle speed and road adhesion coefficient. Comparing with the constant steering ratio, the variable steering ratio calculated by designed function could improve the lateral stability and the handling performance effectively on high-speed and low adhesion road.

Online publication date: Tue, 04-Oct-2022

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