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This paper focuses on platoon control of autonomous vehicles (AVs) equipped with V2X technology and the phenomenon that the large platoons are split into multiple sub-platoons due to the communication restrictions. At the same time, with the popularity of AVs and connected human-driven vehicles (CVs), this paper also carries out the research of mixed traffic flow mixed with AV platoons, CVs and regular human-driving vehicles (RVs). According to the characteristics of the different types of vehicles, this paper extends the corresponding car-following models based on intelligent driver model (IDM), and considers the functional degradation of AVs under different car-following modes. In this paper, the AVs are classified into the second-level degenerated AV (D2AV), the first-level degenerated AV (D1AV) and the normal functioning AV (NAV) based on the differences in car-following modes. The degradation of AVs is represented via the change of communication topologies and models. Linear stability analysis is conducted. Numerical simulation shows that the higher level of AV degradation, the worse the stability of traffic flow. Under the same conditions, the more sub-platoons and the larger maximum size of sub-platoons, the better the stability of the traffic flow. The increase in communication strength of AVs is also beneficial to stability of traffic flow. In order to compensate for degradation, an adaptive gain feedback control strategy is proposed. Simulation shows that the adaptive gain feedback strategy can effectively improve the ability of the traffic flow to resist disturbances, reduce the fluctuations of velocity and acceleration, and contribute to the stability of platoon system and traffic flow. • A general car-following models are established, including eight types of vehicles. • Considering graded degradation, linear stability analysis is conducted. • Exploring the effect of the various factors of sub-platoon on traffic stability. • Proposing an adaptive gain feedback control strategy and proving its effectiveness. [ABSTRACT FROM AUTHOR]

In the real word, the periodic disturbance in traffic flow caused by disrupting maneuvers has a huge impact on the car-following stability. As analyzed in this paper, the asymptotic stability of a car-following model, quantified by the coefficient of dynamic responses, is relatively low at low disturbing frequencies, and gradually increases as the disturbing frequency increases. Fortunately, the development of connected and automated vehicle (CAV) technology and the existing researching works on CAV platoon control have shown great prospect of CAV platooning in the improvement of car-following stability. In order to develop a method to manage the CAV platooning with the explicit purpose of optimizing the car-following stability under periodic disturbance, this study presents an autonomous platoon formation strategy (APFS) for CAV platoon. At certain disturbing frequency, APFS can automatically split a large CAV car-following group into a leading CAV and a number of small CAV platoons, and all CAVs in each platoon follow either the last CAV in the previous platoon or the leading CAV, abiding by the newly designed platoon-based IDM (P-IDM) car-following strategy, so that the overall car-following stability of the CAV group can be optimized. Results of numerical simulations demonstrate that, compared with several existing platoon control strategies, the proposed APFS is capable of significantly enhancing the stability of CAV car-following group, as well as passenger comfort and fuel economy of CAVs, under various types of periodic disturbance. In general, APFS works most effectively when the disturbing frequency is around 0.4 ∼ 0.6 rad/s. Therefore, the proposed APFS shows good potentials in mitigating the oscillation in traffic flow due to periodic perturbations and improving the asymptotic stability of CAV car-following groups. • The asymptotic stability of car-following model under periodic disturbance is analyzed. • A coefficient of dynamic response is defined to quantify the car-following stability under periodic disturbance. • A platoon-based IDM (P-IDM) strategy is designed to elevate the car-following stability of CAV platoon. • An autonomous platoon formation strategy (APFS) is proposed to optimize the car-following stability of CAV platoon. [ABSTRACT FROM AUTHOR]

The coordination and the energy consumption are very important for the platooning of connected and automated vehicles (CAVs). A novel cooperative optimal control for CAVs platoon on basic freeway sections is proposed in this paper. A cost function is designed to address the cooperation of followers, the motion synchronization with the leading vehicle and appropriate energy consumptions. A third-order consensus strategy is suggested to design the control input. A more effective and flexible spacing strategy is introduced. The asymptotically stability and string stability conditions of the system are established. By constructing and solving the LMI optimization problem, the optimal control gains are derived and the global cost function is minimized to a specific upper bound. Numerical simulations are performed on several specific traffic scenarios. The results demonstrate the effectiveness of the presented modeling method. • A novel cooperative optimal control method for CAVs platoon is developed. • A cost function is designed to achieve the cooperative performance and appropriate energy consumption. • A third-order consensus strategy is proposed to design the control input. • The stability conditions and optimal control gains are derived. [ABSTRACT FROM AUTHOR]