安全距离-时间模型的汽车紧急制动分层控制策略研究

Research on the hierarchical control strategy of automobile emergency braking system based on safety distance-time model

为提高汽车紧急制动系统对复杂工况的适应能力,提出安全距离-时间模型相结合的汽车紧急制动系统分层控制策略,分析了危险目标判断控制器的判断逻辑。基于安全时间模型,采用模糊控制理论设计了以本车、相邻车辆的侧向相对距离与相对速度为输入变量,以相邻车道车辆切入本车道的概率为输出变量的车辆换道模糊判断控制器,对相邻车道换道车辆进行判断。通过安全时间模型分别计算换道车辆的“横向碰撞时间TTC_(y)”和本车道前方车辆的“纵向碰撞时间TTC_(x)”,综合判断系统前方危险目标车辆。根据本车与危险目标的相对位置,设计了安全距离和安全时间模型相结合的自动紧急制动系统上层控制器,获得本车期望加速度。构建了基于PID控制的汽车紧急制动系统下层控制器,实现期望加速度与本车制动主缸压力的转化,完成预警/分级制动功能。利用Matlab中Stateflow模块构建了本车安全行驶状态、预警状态及分级制动状态间的切换逻辑状态流模块,在CarSim中设置了车辆纵向动力学及其逆向模型,并在Matlab/Simulink中设计了节气门/制动压力控制分配逻辑仿真模块。基于C-NCAP典型测试工况,进行了控制策略的CarSim与Matlab/Simulink联合仿真验证,结果表明:该策略能够准确地判别换道行为并识别危险目标,具备预警/分级制动功能,可有效避免追尾事故。

In order to improve the adaptability of AEB system in complex working conditions,a hierarchical control strategy is proposed based on safety range-time model.Adopting fuzzy control theory,a danger target judgment controller is designed to judge the lane changing vehicles in adjacent lanes and the danger target ahead of the system is determined based on the safety time model.According to the relative position of the vehicle and the danger target,the upper controller of the automatic emergency braking system which combines the safety distance and safety time model is designed,and the expected acceleration of the vehicle is obtained.The lower level controller of AEB system based on PID control theory is constructed to realize the conversion between the expected acceleration and the master cylinder pressure of the vehicle braking,and complete the warning/hierarchical braking function.Based on the C-NCAP typical test cases,the co-simulation were carried out to verify the control strategy with CarSim and Matlab/Simulink.The results show that this strategy can accurately distinguish lane change behavior and identify dangerous targets,and has the function of early warning/graded braking,which can effectively avoid rear-end collisions.