网联环境下基于速度引导的车辆能耗优化方法

传统的车速引导策略考虑交通信号的信号配时（signal phases and timing，SPAT）信息和到下游交叉口的距离，来对车辆进行速度建议和引导，以提高交叉口通行效率、减少能源消耗。但由于通信设备频率的限制，实时诱导效果欠佳。随着车载设备与路侧基础设施通信技术（vehicle to infrastructure，V2I）的发展，能实时、同步地获取交通流的多维信息，研究了1种符合真实驾驶场景的实时变速引导策略。以信号相位时间和道路通行限制条件为约束，构建三阶段变速诱导模型。提出将车辆通过连续路口的车速引导问题分解为车辆通过多个相邻路口的子问题进行求解。针对任意相邻2个交叉口，求解车辆到达下游交叉口的可通行时间区域，并将到达时间区域离散化，计算车辆到达时间区域内的每1个时间节点的能耗。将连续路口车速引导问题转换为速度轨迹寻优问题进行求解，以车辆能耗为权重，采用Dijkstra算法在所有可通行速度轨迹中寻找能耗最小的速度轨迹。利用交通仿真软件SUMO搭建仿真环境，并用Python对SUMO进行二次开发，以武汉市经济开发区东风大道的3个连续路口为研究对象进行仿真验证。实验结果表明：所提车速引导方法在过饱和，饱和、欠饱和流量下，与多级最优策略相比能耗分别减少0.68%，1.64%，3.97%，与匀速策略相比能耗分别减少0.7%，2.60%，9.80%。所提变速诱导方法在不同交通流量情况下均能诱导车辆节能地驶离交叉口，在欠饱和流量下效果最佳。

A Method for Optimizing Vehicle Energy Consumption Using Speed Guidance in A Connected Vehicle Environment

Based on the signal phases and timing of traffic lights and the distance to the downstream intersection, traditional speed guidance strategies provide advisory speed, in order to improve the efficiency of road transportation and reduce vehicle energy consumption. However, it is difficult to recommend and guide the speed of vehicles in real time due to the limitation of traditional communication methods. With the development of vehicle to infrastructure (V2I) technology, it is possible to access multi-dimension information of traffic flow instantly and simultaneously, and a real-time variable speed guidance method, which can adapt to real-world driving scenarios, is proposed. A three-stage variable speed guidance model is developed by considering signal phase time and road capacity as the constraints. Moreover, the speed guidance problem of vehicle crossing multiple intersections is decomposed into sub-problems defined by each pair of consecutive ones. Between any two adjacent intersections, the feasible time range for vehicle arriving at the downstream junction is solved first, and then it is discretized to calculate the energy consumed at each time node. In the meantime, the speed guidance problem for vehicle traveling through continuous intersections is transformed into an optimal speed control problem. Taking energy consumption of vehicles as the weight, a Dijkstra algorithm is applied to compute the desired path that generates the most efficient speed profile with the lowest energy consumption among all feasible options. The simulation is conducted to verify the proposed method using the simulation of urban mobility (SUMO) simulator, and a case study is carried out for three consecutive intersections of Dongfeng Avenue in Wuhan Economic Development District. Experimental results show that, under scenarios of oversaturated, saturated, and undersaturated traffic flow, the proposed speed guidance method can reduce energy consumption by 0.68%, 1.64%, and 3.97%, when compared with the multi-level optimal method; and by 0.7%, 2.60%, and 9.80%, when compared with the constant speed method, respectively. The proposed variable speed guidance method can provide an energy-efficient trajectory for vehicles to pass through intersections under different traffic volumes and performs best in an undersaturated traffic flow condition.