Design and Validation of Trajectory Tracking Controller for Autonomous Vehicle Based on Linear Time-varying MPC Method
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摘要: 随着自动驾驶技术的快速发展,精确的轨迹跟踪已经成为汽车工业和学术领域公认的实现自主车辆运动控制的核心技术之一。为提高自主车辆轨迹跟踪的实时性与准确性,提出一种应用于自主车辆的线性时变模型预测跟踪控制器(Linear time-varying model predictive controller, LTV-MPC)设计方法。根据运动学原理建立某自主无人小车的二自由度运动学模型,其次,基于该模型构建车辆轨迹跟踪系统的误差模型并利用线性参数化理论对其进行离散化,在模型预测控制框架内将该轨迹跟踪控制器的设计转化为一个线性二次规划最优问题。在一个实际搭建的自主车辆试验平台上对所提出控制器的有效性进行不同预设参考路径轨迹下的实车验证,结果表明,该自主车辆能够对所预设的实际参考道路轨迹进行快速、准确的轨迹跟踪控制,且具有较好的行驶稳定性能。Abstract: With the rapid development and implementation of autonomous driving technology, accurate trajectory tracking for such autonomous vehicles(AVs) has become one of core techniques for fulfilling the AVs motion control in automobile industry and academic research areas. To improve the real-time and accuracy performance of trajectory tracking for the AVs, it is proposed a comprehensive linear time-varying model predictive controller(LTV-MPC) applied to a certain AV. First, a two-degree-of-freedom kinematic model of an AV is constructed in terms of vehicle kinematics principle, Next, based on this 2-DOF kinematic model of AV, a dynamic error model of vehicle's trajectory tracking system is derived using linear time-varying theory, and this model is then linearized by a successive linearization, and the design of this desirable trajectory tracking controller is transformed to a quadratic programming optimized problem in the framework of model predictive control. Finally, the effectiveness of the proposed controller is validated on a self-established test platform under various prescribed reference road trajectories, the results show that this AV with the proposed LTV-MPC can track the prescribed reference road trajectories with high speed and precision, as well as good stability for the AV under various driving conditions.
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表 1 车辆运动学模型参数
符号 描述 A$ ({X_{\rm{f}}}, {Y_{\rm{f}}}) $ 前轴轴心 B$ ({X_{\rm{r}}}, {Y_{\rm{r}}}) $ 后轴轴心 $ \varphi $ 车身横摆角 $ {v_{\rm{r}}} $ 后轮速度 $ l $ 轴距 $ {\delta _{\rm{f}}} $ 前轮偏转角 R 瞬时转向半径 P 瞬时转向中心 $ \omega $ 车身横摆率 表 2 无人自主小车参数
名称 数值 轴距l/cm 26 后轮速度$ {v_{\rm{r}}} $/(m/s) 1 舵机工作电压/V 6.6 舵机扭力/(kg/cm) 13 直流电机KV值 13.5 T-3400 KV 电池工作电压/V 7.4 -
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