Abstract: In order to improve the maneuvering stability of a vehicle with steer-by-wire control, this paper firstly investigates the vehicle response in different speed domains to determine the change characteristics of the vehicle steady state gain. Secondly, the vehicle response of different steering wheel input frequencies is analyzed, and the steering input frequency is taken as the threshold condition for mode switching. Then, the relationship between the steering wheel center position and the "dead zone" is investigated to design the incremental law of the transmission ratio. Finally, a fuzzy controller with variable structure ratio is designed based on multi-factor analysis, and simulation is carried out under typical working conditions. The results show that the turning radius of the vehicle under low speed is obviously smaller than that of the mechanical steering system in the steady state slewing test condition, and the response of the swing angle speed decreases with the increase of the vehicle speed, but it is still higher than that of the mechanical steering system, which is in line with the design requirements of the ideal transmission ratio. Meanwhile, in the intermediate steering test condition, the lateral displacement of the vehicle under this strategy is smaller, which is in line with the expectation that a larger steering input is required in the intermediate steering position.

Key words: Steer-by-wire; Fuzzy control; Turn to input frequency; Variable angle transmission ratio

摘要： 为了提高线控转向车辆的操纵稳定性，文章首先在不同速域下对车辆响应进行研究， 确定车辆稳态增益的变化特征。其次对不同方向盘输入频率的车辆响应进行分析，确定以转 向输入频率为模式切换的阈值条件。然后对方向盘中位与“死区”的关系进行探究设计传动 比的增量规律。最后，基于多因素的分析设计变结构传动比模糊控制器，并通过典型工况进 行仿真研究。结果表明，在稳态回转试验工况下该策略在低车速下车辆转弯半径明显小于机 械转向系统，并随着车速的提高横摆角速度响应降低但仍高于机械转向，这符合理想传动比 的设计要求。同时在中间转向试验工况中，该策略下的车辆横向位移更小，符合在中间转向 位置需要较大转向输入的预期。

关键词: 线控转向；模糊控制；转向输入频率；变角传动比