Design of Variable Steering Ratio for Steer-by-Wire System Considering the Driver’s Handling Skill

To address the sluggishness issue during steering for novice drivers and enhance the vehicle’s stability during steering for experienced drivers, this paper proposes a variable steering ratio (VSR) design method for steer-by-wire (SBW) system considering the driver’s handling skill. Firstly, a driver-vehicle closed-loop system is constructed, mainly consisting of the vehicle, driver, and SBW system models. Secondly, a comprehensive handling stability evaluation index associating trajectory tracking error, direction error, and rollover risk error is presented, along with a steering sensitivity evaluation index considering yaw rate and front wheel steering angle response. Thirdly, incorporating the driver’s handling skill into the ideal VSR design, a personalized VSR design approach is proposed, which can provide the desired steering ratio for different types of drivers. Finally, simulations are conducted under double lane-change and slalom tests to prove the feasibility and applicability of the proposed approach. The results demonstrate that compared to the ideal VSR design method, the personalized design method can reduce the handling stability evaluation index for experienced drivers by 7.3% to 9.7%, and increase the steering sensitivity evaluation index for novice drivers by 6.4% to 10.6% under different driving conditions when turning.