Homogeneous platoon speed planning and following control in front vehicle cut-in and cut-out conditions
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摘要: 针对匀质队列定速巡航时前车切入切出可能导致碰撞风险以及跟随控制效率低、稳定性差的问题,提出一种前车切入与切出工况下匀质队列速度规划与跟随控制模型,基于卷积神经网络-门控循环单元(CNN-GRU)混合网络建立轨迹预测模型,以预测未来一段时域内的前车换道轨迹;通过构建纵向位移与时间的关系,确定了前车的切入或切出状态,搭建了跟随车速度跟随模型,并进行了队列整体速度规划;建立了模糊线性上层控制器,根据车速差输出符合驾驶场景需求的期望加速度;结合纵向逆动力学模型和模糊比例-积分-微分(PID)控制建立了下层控制器,将期望加速度转化为驱动转矩或制动压力,从而直接控制车辆;为进一步验证提出的控制模型的有效性,搭建了PreScan/CarSIM/SIMULINK联合仿真平台,设计了相邻前车切入和切出时的仿真工况,并将提出的控制模型与自适应巡航控制(ACC)方案进行了对比。研究结果表明:应用提出的控制模型后,所有信息流拓扑结构队列中均未出现追尾现象,且最大间距误差、全局平均速度跟踪误差和局部平均速度跟踪误差分别至少降低了55.9%、40.6%和42.0%。由此可见,提出的控制模型在前车切入与切出工况下不仅能避免潜在的追尾事故,而且可以有效缩短队列车辆间的最大间距,减小队列的速度跟踪误差,有利于提升队列的跟随效率和行驶稳定性。Abstract: To solve the problems that the front vehicle cut-in and cut-out may lead to a collision risk, as well as the low efficiency and poor stability of following control during constant speed cruise of the homogeneous platoon, a homogeneous platoon speed planning and following control model in front vehicle cut-in and cut-out conditions was proposed. Based on the convolutional neural network-gated recurrent unit (CNN-GRU) hybrid network, a trajectory prediction model was established to predict the lane change trajectory of front vehicle within a future time domain. By constructing the relationship between longitudinal displacement and time, the front vehicle cut-in or cut-out state was determined. The speed following model of following vehicles was built, and the overall speed planning of the platoon was carried out. A fuzzy linear upper controller was established to output the desired acceleration according to the speed difference meeting the driving scenario requirements. Combining the longitudinal inverse dynamics model and fuzzy proportional integral derivative (PID) control, a lower controller was established to convert the desired acceleration into the driving torque or braking pressure. Thus, the direct control of the vehicle was achieved. To further verify the effectiveness of the proposed control model, a PreScan/CarSIM/SIMULINK co-simulation platform was built, simulation conditions for the adjacent front vehicle cut-in and cut-out were designed, and the proposed control model was compared with the adaptive cruise control (ACC) scheme. Research results show that after applying the proposed control model, no rear-end coallision occurs in platoons for all information flow topologies, and the maximum spacing difference, global average speed tracking error and local average speed tracking error reduce at least 55.9%, 40.6% and 42.0%, respectively. Therefore, the proposed control model can not only avoid potential rear-end collisions in front vehicle cut-in and cut-out conditions, but also can effectively shorten the maximum gap between platoon vehicles, reduce the speed tracking error of the platoon, and help to improve the following efficiency and driving stability of the platoon.
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表 1 驾驶人年龄、驾龄分布
Table 1. Driver age and driving experience distributions
驾驶人分类特征 特征分布 试验人员数 年龄分布/岁 20~30 4 31~45 4 其他 2 驾龄分布/年 3 2 4 2 5 2 6 2 7 2 表 2 线性控制单元控制增益
Table 2. Control gains of linear control unit
信息流拓扑结构 k BD (6, 13, 6)T 其他 (0.5, 1.2, 0.6)T 表 3 模糊推理系统中各变量论域
Table 3. Variable universes in fuzzy reasoning system
拓扑结构 变量 论域 BD e [-1, 1] ec [-3, 3] ΔKv [0, 5] 其他 e [-2, 2] ec [-3, 3] ΔKv [0, 0.6] 表 4 模糊推理系统规则
Table 4. Fuzzy reasoning system rules
ΔKv ec NH NC NL Z0 PL PC PH e NH NH NH NC NC NC NC NC NC NH NH NH NH NH NH NC NL NH NH NH NH NC NC NL Z0 NH NH NH NH NH NC NC PL NC NC NC NL NL Z0 Z0 PC PH PH PH PH PH PH PH PH PH PH PH PH PH PH PH 表 5 平均y坐标位置误差的平均值
Table 5. Average values of average y-coordinate position errors
m 预测模型 不同预测时域(s)下的误差平均值 1 2 3 4 CNN-GRU 0.143 0.258 0.786 0.749 CNN-LSTM 0.199 0.208 0.741 0.824 GRU 0.304 0.735 0.886 0.902 表 6 最终y坐标误差的平均值
Table 6. Average values of final y-coordinate errors
m 预测模型 不同预测时域(s)下的误差平均值 1 2 3 4 CNN-GRU 0.165 0.240 0.447 0.473 CNN-LSTM 0.193 0.172 0.539 0.686 GRU 0.409 0.735 0.997 1.026 表 7 平均x坐标误差的平均值
Table 7. Average values of average x-coordinate errors
m 预测模型 不同预测时域(s)下的误差平均值 1 2 3 4 CNN-GRU 2.909 3.604 3.299 3.974 CNN-LSTM 5.293 5.174 5.741 5.762 GRU 7.265 8.374 9.545 9.897 表 8 最终x坐标误差的平均值
Table 8. Average values of final x-coordinate errors
m 预测模型 不同预测时域(s)下的误差平均值 1 2 3 4 CNN-GRU 2.709 2.707 2.954 4.089 CNN-LSTM 5.148 5.153 3.762 5.779 GRU 7.993 9.978 10.142 11.481 表 9 最大间距差对比
Table 9. Comparison of maximum spacing difference
m 拓扑结构 模糊控制策略 对比策略 PF 2.464 7 2.758 9 PLF 2.118 5 2.193 5 BD 0.927 1 0.947 8 BDL 2.118 4 2.193 3 TPF 2.118 5 2.193 5 TPLF 2.118 5 2.193 5 表 10 全局平均速度跟踪误差对比
Table 10. Comparison of global average speed tracking error
m·s-1 拓扑结构 模糊控制策略 对比策略 PF 0.510 2 0.605 0 PLF 0.083 8 0.089 3 BD 0.115 7 0.121 8 BDL 0.083 9 0.089 3 TPF 0.184 2 0.201 4 TPLF 0.083 5 0.089 0 表 11 局部平均速度跟踪误差对比
Table 11. Comparison of local average speed tracking error
m·s-1 拓扑结构 PF BD TPF 模糊控制策略 0.534 2 0.098 6 0.126 7 对比策略 0.645 9 0.104 0 0.279 8 表 12 最大间距差对比
Table 12. Comparison of maximum spacing difference
m 拓扑结构 速度跟随策略 对比策略 PF 2.717 9 6.487 5 PLF 2.171 9 4.925 3 BD 0.866 2 1.978 3 BDL 2.171 9 4.925 3 TPF 2.171 9 4.925 3 TPLF 2.171 9 4.925 3 表 13 全局平均速度跟踪误差对比
Table 13. Comparison of global average speed tracking error
m·s-1 拓扑结构 速度跟随策略 对比策略 PF 1.1387 2.182 9 PLF 0.1811 0.305 1 BD 0.2242 0.386 5 BDL 0.1811 0.304 9 TPF 0.4049 0.691 7 TPLF 0.1811 0.304 9 表 14 局部平均速度跟踪误差对比
Table 14. Comparison of local average speed tracking error
m·s-1 拓扑结构 PF BD TPF 速度跟随策略 1.197 0 0.189 4 0.279 8 对比策略 2.347 6 0.331 0 0.483 2 -
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