Abstract:

A new road wheel angle distribution algorithm of the AIFS system proposed in recent years was presented based on control allocation, in terms of the fact that the rule-based allocation algorithm might cause lower adaptivity and an optimal result was obtained difficultly. The shortcomings of active front steering (AFS) system were indicated firstly, and the structure and principles of the AIFS system were introduced. Furthermore, a sliding mode controller of AIFS was developed to obtain the desired yaw moment and an optimization-based allocator was employed to determine the optimal split between the outer road wheel angle and inner road wheel angle. Finally, the control strategy was evaluated by simulating vehicle responses to the J-turn steering input. Simulation results obtained using a 4-DOF vehicle model performed in MATLAB/Simulink environment demonstrate that the AIFS can automatically adjust the size of wheel angles according to the tire load transfer, and achieve better performances than that of AFS in tracking the ideal yaw rate and the ideal trajectory so that the tires with heavier load make more contributions, thus the vehicle has an excellent lateral stability.

Key words: vehicle engineering, active independent front steering(AIFS), control allocation, vehicle stability

摘要：

针对新近提出的主动前轮独立转向(AIFS)系统基于规则的转角分配方法自适应性差、无法实现最优分配的问题，提出了一种基于控制分配的转角分配算法。指出了传统主动前轮转向(AFS)存在的问题，阐述了主动前轮独立转向系统的结构和工作原理;在MATLAB/Simulink中建立了整车四自由度数学模型，设计了AIFS滑模控制器和转角分配模块;通过阶跃转向工况对所提出的转角分配算法进行了仿真验证。结果表明：该分配算法可以使AIFS自适应内外轮载荷转移变化，自动调整内外轮转角大小，较AFS可以更好地跟踪理想横摆角速度和理想运动轨迹，实现了“能力越大的轮胎贡献越大”的控制目标，提高了车辆极限转弯时的侧向稳定性。
 

关键词: 车辆工程, 主动前轮独立转向, 控制分配, 车辆稳定性