汽车高速紧急避障路径跟踪与主动防侧翻控制

Research on high speed path tracking and rollover control for obstacle avoidance under emergency of vehicle

摘要:

为提高匹配机械弹性车轮汽车在高速紧急避障时的效率与安全性,在Simulink中建立了整车非线性八自由度模型,并基于车轮样机台架试验数据,利用Matlab 遗传算法工具箱对机械弹性车轮模型参数进行分级辨识. 综合考虑行驶车速、轨迹跟踪误差、方向盘转角以及侧翻评价指标,建立了八自由度驾驶员—汽车预瞄跟随闭环系统模型. 分析了汽车在不同行驶车速时所需的方向盘角输入信息与侧翻状态响应,总结出汽车高速转向时的侧翻动态特性. 为高速安全通过规划的避障路径,在转向控制驾驶员模型基础上建立了速度控制驾驶员模型,当侧翻评价指标超过安全阈值时利用制动踏板降低车速,当纵向车速小于期望安全车速时利用加速踏板提高车速. 仿真分析表明建立的高速避障路径跟踪与控制策略能高效完成避障路径跟踪,同时能有效降低紧急避障时的侧翻风险.

Abstract:

In order to improve the efficiency and safety in high speed obstacle avoidance under emergency of vehicle with mechanical elastic wheel (MEW), a nonlinear eight-degree of freedom (8-DOF) vehicle model for dynamics simulation was built up by Simulink. The parameters of MEW tire model were identified by Matlab genetic algorithm toolbox according to the experimental data of flat-bed test rig. Considering the driving speed, the trajectory deviation, the steering wheel angle and the rollover evaluation index, an 8-DOF driver-vehicle closed loop system was established. The driving speed and steering properties of driver-vehicle model to rollover stability are analyzed. For high speed path tracking and rollover control under emergency obstacle avoidance of vehicle, the speed control driver model is established based on steering control driver model, which utilizes a predictive load transfer ratio (PLTR) as the rollover index and the rollover controller activates only when the potential for rollover is significant, otherwise, acceleration control strategy will be used for minimum time obstacle avoidance when the longitudinal velocity is less than the expected safety velocity. Simulation results show that the proposed control strategy has good accuracy in both path and speed following and has a better stability of rollover under emergency situation.