Abstract: Two-degree-of-freedom model of four-wheel steering system was established based on the risk of the same direction of mass center sideslip angle and yaw rate and the contradiction of reverse control strategy in the high-speed driving process of the four-wheel steering system. A reduced order state observer was designed to solve the problem that the sideslip angle of vehicle centroid was difficult to be measured by existing sensors. Then, the pole assignment method and LQR (linear quadratic optimal control) method were used to design the controller respectively, and a control law design method which weighted the state regulator and the target yaw rate tracking was proposed. MATLAB/Simulink was used to simulate the step mode and the single line transfer mode. The results show that the steady-state yaw rate decreases slightly, but it can significantly improve the track ability of the vehicle.

Key words: vehicle engineering, four-wheel steering, state observer, linear quadratic, sideslip angle of centroid, yaw rate

摘要： 针对车辆高速行驶过程中，四轮转向系统产生的质心侧偏角和横摆角速度方向同向危险性及反向控制策略的矛盾性，建立四轮转向系统二自由度模型。设计一种降维状态观测器解决车辆质心侧偏角难以被现有传感器测得的问题，进而分别运用极点配置法和线性二次型最优控制(LQR)两种方法设计控制器，提出了一种对状态调节器和目标横摆角速度跟踪进行加权的控制律设计方法；通过MATLAB/Simulink应用阶跃工况和单移线工况进行仿真试验，其结果显示：稳态时横摆角速度减少较小，却能够显著提高车辆的路径跟踪能力。

关键词: 车辆工程, 四轮转向, 状态观测器, 线性二次型, 质心侧偏角, 横摆角速度