A Lateral Control Strategy for Unmanned Vehicle Path Tracking using State Feedback
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摘要: 针对采用传统模型预测控制器的车辆在弯道内跟踪精度难以保证的问题, 本文提出了一种基于状态反馈的路径跟踪横向控制策略。基于车辆动力学模型, 建立考虑轮胎滑移包络线约束条件的路径跟踪模型预测控制器, 并根据车速选择合适的控制器时域参数; 以车辆质心位置为控制点建立车辆跟踪误差模型, 结合车辆当前位置横摆角偏差建立状态反馈调节器, 通过LQR最优控制方法对无人车姿态进行校正。利用MATLAB/Simulink和Carsim软件对改进的状态反馈控制策略进行了仿真验证, 典型双移线道路仿真试验表明: 中低车速下车辆路径跟踪横向偏差降低了16 %以上, 横摆角偏差降低了33 %以上, 所设计控制器能够有效提高车辆路径跟踪精度, 可保证车辆对变曲率弯道具有适应性和行驶稳定性。Abstract: Because it is difficult to guarantee the tracking accuracy of an unmanned vehicle in its bending path with the traditional model predictive controller, this paper proposes a lateral control strategy for the path tracking based on state feedback. Based on the vehicle dynamics model, the path tracking model predictive controller that considers the constraints of the tire slip envelope of the unmanned vehicle is established, and the appropriate time-domain parameters of the controller are selected according to the speed of the unmanned vehicle; its tracking error model is established by using the centroid position of the vehicle as control point. The state feedback regulator is established by combining the yaw angle deviations of the current position of the vehicle, and the attitude of the unmanned vehicle is corrected with the LQR optimal control method. The improved state feedback control strategy is simulated and verified with the MATLAB/Simulink software and the Carsim software. The typical double lane change simulation results show that the lateral deviation of the vehicle's path tracking is reduced by more than 16% and the yaw angle deviation is reduced by 33% at low and medium speeds. Above all, the controller improved in the paper can effectively improve the path tracking accuracy and ensure the adaptability and driving stability of an unmanned vehicle on various curvature bends.
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Key words:
- unmanned driving /
- path tracking /
- model predictive control /
- state feedback regulator
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表 2 车辆参数及权重矩阵设置
模型参数 数值 整车质量m/kg 1 723 车辆轴转动惯量Iz/(kg·m2) 4 175 质心距前轴距离a/m 1.04 质心距后轴距离b/m 1.56 前轮侧偏刚度Cf/(N·rad-1) -66 900 后轮侧偏刚度Cr/(N·rad-1) -62 700 路面附着系数μ 1 车辆滑移率s 0.2 离散时间步长tp/s 0.04 权重系数ρ 1 000 输出量的权重矩阵Q [200, 100, 10, 10] 控制量的权重矩阵R 50 000 前轮转角δf/(°) [-10, 10] 
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表 3 双移线工况横向偏差对比
车速/(km·h-1) 指标/m 传统MPC 状态反馈MPC 改善程度/% 36 平均偏差 0.165 0.138 16.5 最大偏差 0.518 0.353 31.7 72 平均偏差 0.225 0.148 34.0 最大偏差 0.681 0.454 33.3 108 平均偏差 0.512 0.494 3.3 最大偏差 1.261 1.350 -7.0
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表 4 双移线工况横摆角偏差对比
车速/(km·h-1) 指标/m 传统MPC 状态反馈MPC 改善程度/% 36 平均偏差 0.029 0.019 35.1 最大偏差 0.089 0.059 33.4 72 平均偏差 0.018 0.007 61.5 最大偏差 0.070 0.027 61.1 108 平均偏差 0.035 0.030 14.7 最大偏差 0.110 0.092 16.2
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