四轮独立转向无人车辆斜向行驶轨迹跟踪控制方法

针对四轮独立转向电动汽车转向系统成本高、但功能开发程度低的问题，提出一种车辆斜向行驶控制策略，优化四轮独立转向电动汽车换道过程中的行驶稳定性. 基于四轮独立转向电动汽车横向、纵向二自由度车辆模型，提出一种横纵向耦合轨迹跟踪控制方法，该方法基于线性时变模型采用模型预测控制（MPC）算法，对横向偏差、航向角偏差及纵向速度偏差进行闭环控制. 设计车辆稳定性控制器，包括横摆力矩控制器和转矩分配控制器，同时提高车辆轨迹跟踪精度和行驶稳定性. 最后搭建Simulink/Carsim/Prescan联合仿真平台，对四轮独立转向电动汽车双移线工况进行模拟换道仿真，仿真结果证明了斜向变道的可行性和横纵向耦合轨迹跟踪控制方法的有效性. 

Trajectory Tracking Control Strategy for Oblique Driving of 4WIS Unmanned Vehicle

Aiming at the problem of high cost of steering system of four-wheel independent steering electric vehicle (4WIS-EV) and less functional development, a vehicle oblique driving control method was proposed to optimize the driving stability of 4WIS-EV during lane changing. Firstly, based on the 4WIS-EV lateral and longitudinal two-degree-of-freedom vehicle model, a lateral and longitudinal coupled trajectory tracking control method was proposed. According to linear-time-variant (LTV) model and model predictive control (MPC) algorithm, a closed-loop control of lateral deviation, heading angle deviation and longitudinal speed deviation was carried out. And then, a vehicle stability controller was designed, including yaw moment controller and torque distribution controller to improve trajectory tracking accuracy and driving stability simultaneously. Finally, a Simulink/Carsim/Prescan co-simulation platform was built to carry out the lane-changing simulation of the 4WIS-EV in double-line shifting condition. The simulation results show the feasibility of the oblique lane change and the effectiveness of the lateral and longitudinal coupled trajectory tracking control method.