面向进出站强制换道过程的智能网联公交车两车协同换道策略

Two-vehicle cooperative lane change strategy for intelligent and connected buses in the mandatory lane change process of entry and exit

目前针对智能网联公交车换道策略的研究多基于单车智能实现,缺少对周围车辆的考虑,难以处理车间冲突,无法同时保障公交车进出站强制换道的安全性和成功率,且容易对上游交通造成影响。该文旨在面向公交车进出站强制换道过程,提出一种基于云控系统的两车协同换道策略。针对进站过程,建立了基于换道收益准则的换道决策模型,制定了包含纵向调整、协同换道的两段式滚动时域轨迹规划方法,并基于分层二次规划改善算法实时性;针对出站过程,采用基于规则的决策方法和提前减速策略,制定了考虑港湾式车站特点的轨迹规划方法,以适应车站形状和公交车机动性的要求。仿真和硬件在环实验表明:该策略能够有效提升公交车进出站强制换道的成功率,并在保障换道安全的同时降低对上游交通的影响,且在真实云平台的运算、通信环境下具备可用性。

[Objective]The process of buses entering and exiting a station often accompanies mandatory lane change,which can significantly impact traffic safety and efficiency.However,current research on lane change strategies for intelligent and connected buses relies on single-vehicle algorithms,lacking consideration for surrounding vehicles and facing challenges in handling inter-vehicle conflicts.These approaches also struggle to ensure the safety and success rate of mandatory lane change during entry and exit,and easily impact the traffic flow.To improve the performance of mandatory lane change for intelligent and connected buses during the entry and exit processes,a two-vehicle cooperative lane change strategy based on the cloud control system(CCS)is proposed,which can schedule buses and cooperating vehicles simultaneously.[Methods]This study designed a set of cooperative lane change strategies for the entry and exit processes.For the entry process,the road segment leading to the bus station was divided according to the distance to the station,and a decision-making model based on the lane change benefit criterion was established.A two-stage trajectory planning method was developed for lane change trajectories,incorporating the longitudinal adjustment and cooperative lane change stages.Optimization problems were formulated and solved in a receding horizon to obtain the optimal trajectories.A layered quadratic programming method was also employed to improve the real-time performance of the algorithm.For the exit process,to adapt to the characteristics of the exiting motion of buses,a rule-based decision-making method and pre-deceleration rule were designed.Lane change trajectories were optimized considering the characteristics of bay-style bus stations to meet the station shape and bus mobility requirements.Finally,the NGSIM dataset was used to design typical scenarios for simulation and hardware-in-the-loop experiments.The effectiveness of the proposed strategy was tested.The proposed strategy was also compared with baseline methods,i.e.,the minimizing overall braking induced by lane change(MOBIL)decision model along with the fifth-order polynomial single-vehicle planning method,and the rule-based decision model along with the fifth-order polynomial single-vehicle planning method for the entry and exit processes,respectively.[Results]The simulation and hardware-in-the-loop experiments under typical scenarios demonstrate that the proposed strategy can effectively adapt to realistic vehicle speed changes,assisting buses in completing lane changes during station entry and exit.Moreover,when faced with the actual computing and communication environment of the cloud platform,the proposed strategy meets the requirements for real-time and effective calculations.The comparison with the baseline method shows that,in batch tests for station entry and exit,the lane change success rates of the proposed strategy were 87.4%and 82.4%,respectively,both higher than the baseline method's 51.9%and 20.4%,respectively.Evaluation metrics based on the following vehicle's speed,acceleration,and time to collision(TTC)also indicate that,compared with the baseline method,the proposed strategy can reduce the impact of mandatory lane change on traffic efficiency while maintaining better safety standards.[Conclusions]Using the CCS to achieve centralized decision-making and trajectory planning for scheduling buses and cooperating vehicles simultaneously,the proposed strategy can effectively handle mandatory lane change under high traffic density conditions.The proposed strategy not only improves the success rate of mandatory lane changes for buses entering and exiting stations,but also ensures lane change safety and reduces the impact on upstream traffic.The proposed strategy is also applicable in cloud platforms under realistic computing and communication environments.