四轮独立转向汽车转向控制器线性优化设计
Linear Optimal Design of Steering Controller of Four Wheel Independent Steering Vehicle

建立以四轮侧偏角为输入的四轮独立转向车辆二自由度动力学模型。以四轮侧偏角绝对值之和为最小值，构建包含前馈和反馈控制的性能指标函数。根据动力学模型静态表达式和理想横摆角速度，获得前馈控制约束条件。建立车辆控制模型和理想跟踪模型，获得反馈控制约束。利用优化理论进行控制器求解，并进行仿真分析，讨论了车辆横摆转矩的选取与作用。建立人-车-路闭环仿真模型，进行模拟道路实验和实车低速跟踪实验，验证了控制器可根据路面附着情况分配各轮转角，充分利用路面附着条件，保证轮胎侧偏角处于较好附着区域。实验表明，控制器具有良好的跟踪性和鲁棒性，进一步提高了车辆的操纵稳定性。
The four-wheel independent steering vehicle's dynamics model of two degrees of freedom is established, and its input is the four-wheel tire side slip angle, whose total absolute value is as small as objective function, including feedforward and feedback control. Based on the steady-state expression of the dynamics model and the ideal yaw rate, the constraint condition is obtained for feedforward control. The vehicle control model and the ideal track model are established; the constraint conditions of feedback control are obtained. The optimal theory is used to solve the controller, which is analyzed with the simulation results. The yaw is discussed. The driver-vehicle-road closed-loop system is established; the road simulations and experiments on low-speed vehicle show that the controller distributes the four-wheel steering angle according to the road adhesion coefficient and that it makes the best use of road adhesion conditions and ensures that the tire side slip angle in good adhesion conditions is zero. The experimental results show that the controller has a good tracking performance and robustness, thus improving the vehicle handling stability