考虑路面附着系数和车速的AFS可变传动比设计

Design of AFS variable steering ratio considering road adhesion coefficient and vehicle speed

为了提高车辆在低速转向轻便性和高速转向稳定性,提出了一种基于车速和路面附着系数的转向系统可变传动比函数。分析了转向系统理想传动比曲线设计过程、主动前轮转向(AFS)系统的传动机构,提出的解决方案包括:1)根据车辆实际的横摆角速度增益与理想横摆角速度增益之间的误差变化规律对理想横摆角速度增益进行修正;2)综合考虑车速和路面附着系数对转向系统传动比的影响,推导路面附着系数、车速与转向系统传动比之间的函数关系。在Carsim/Matlab中搭建变比转向系统仿真模型,并进行仿真。结果表明:所设计的传动比函数可以根据不同车速和不同路面附着系数计算出合理的传动比。在低附着路面,可提高车辆的操纵稳定性和转向轻便性。

A variable steering system transmission ratio function was proposed based on considering vehicle speeds and road adhesion coefficients to improve the steering portability at low speed and the steering stability at high speed of vehicles.After analyzed the design process of an ideal transmission ratio curve and the drive mechanism of active front steering(AFS)system,proposed some solutions including:(1)Modifying the ideal yaw rate gain according to the error variation law between the actual yaw rate gain and the ideal yaw rate gain of the vehicle positive;(2)Considering comprehensively the influence of vehicle speeds and road surface adhesion coefficients on transmission ratio with the help of deriving the functional relationship between road surface adhesion coefficients and vehicle speeds and transmission ratios.A simulation model was built for vehicle trajectory tracking in a Carsim/Matlab platform to simulating.The results show that the designed transmission ratio function can calculate the reasonable transmission ratio of steering system at different vehicle speeds and different road adhesion coefficients on low adhesion roads.Therefore,it improves the handling stability and steering portability for vehicles.