Abstract: Aiming at the handling stability problem of vehicle driving, this paper proposes an optimal control method for four-wheel steering vehicles. Firstly, a two-degree-of-freedom four-wheel steering vehicle dynamics model is established by considering the motion relationship between the front and rear wheels. The dynamics model is then derived into a state-space equation. Finally, The sideslip angle of the vehicle's center of mass and the yaw rate are selected as the optimization control objects. Based on the state-space equation, the Q and R weight coefficients and the performance index function of the optimal controller for the rear wheel steering angle are designed. The Riccati equation is solved to minimize the control energy and obtain the ideal rear wheel steering angle. The co-simulation results of CarSim and Simulink show that the optimal control method reduces the average sideslip angle of the vehicle's center of mass by 98%. This method effectively improves the vehicle's handling stability and safety, and has strong robustness.

Key words: four-wheel steering; optimal control; robustness; CarSim-Simulink co-simulation

摘要： 针对汽车行驶的操纵稳定性问题，文章提出了一种四轮转向汽车最优控制方法。首先， 考虑前、后轮运动关系建立二自由度四轮转向汽车动力学模型；其次，将动力学模型推导为 状态空间方程；最后，选取汽车质心侧偏角及横摆角速度作为优化控制对象，基于状态空间 方程设计后轮转角最优控制器的 Q、R 权重系数及性能指标函数，求解黎卡提方程使控制能 量最小化并得到理想后轮转角。CarSim-Simulink 联合仿真对比结果表明，最优控制方法使汽 车质心侧偏角平均降低约 98%，该方法有效提高了车辆的操控稳定性、安全性，且具有较强 的鲁棒性。

关键词: 四轮转向；最优控制；鲁棒性；CarSim-Simulink 联合仿真