CACC车头时距与混合交通流稳定性的解析关系

研究协同自适应巡航控制(Cooperative Adaptive Cruise Control，CACC)车头时距对不同CACC比例下混合交通流稳定性的影响关系，进而为CACC车头时距设计提供参考. 应用优化速度模型(Optimal Velocity Model，OVM)作为手动车辆的跟驰模型，PATH真车实验标定的模型作为CACC车辆的跟驰模型. 基于传递函数理论，推导混合交通流稳定性判别条件，计算关于CACC比例与平衡态速度的混合交通流稳定域. 分析混合交通流在任意速度下稳定所需满足的临界CACC比例与CACC车头时距的解析关系，提出随CACC比例增加的可变 CACC车头时距设计策略，并通过数值仿真实验验证所提可变CACC车头时距策略的正确性. 研究结果表明：在所提可变CACC车头时距策略下，CACC车头时距随CACC比例增加而逐渐降低，避免取值较大影响混合交通流通行能力的提升；当CACC比例大于35%时，混合交通流在任意速度下稳定.研究结果可为大规模CACC真车实验的实施提供理论设计参考.

Analytical Relationship Between CACC Headway and Stability of Mixed Traffic Flow

This paper studies influence of cooperative adaptive cruise control (CACC) headway on stability of mixed traffic flow with different CACC proportions. Then it can provide reference for design of CACC headway. The optimal velocity model (OVM) was used for the car- following model of manual vehicles, while the model calibrated by PATH' s experiments was employed for CACC vehicles. Based on transfer function theory, stability criterion of the mixed traffic flow was derived. Then stability charts with respect to CACC proportions and equilibrium speeds were calculated. The variable design strategy for CACC headway was proposed by analyzing the analytical relationship between CACC headway and critical CACC proportion that will maintain stable mixed flow under any speed. The numerical simulations were also performed to validate correctness of the proposed variable strategy for CACC headway. The results show that the designed values of CACC headway decrease with the increase of CACC proportions under the proposed variable strategy. This avoids impacts of larger values of CACC headway on capacity improvement of the mixed traffic flow. Moreover, the mixed traffic flow can be stable for any speed when the CACC proportion is more than 35%. This paper contributes to the reference for theoretical design of large-scale real CACC implements.