Developing platooning systems of connected and automated vehicles with guaranteed stability and robustness against degradation due to communication disruption

Connected and automated vehicle platooning systems like cooperative adaptive cruise control (CACC) have shown great potential on improving traffic performance with a shortened time gap through advanced sensing and Vehicle-to-Vehicle (V2V) communication technologies. However, V2V communication is not always reliable in realistic traffic conditions. When V2V communication is disrupted, the degradation of the CACC vehicle will occur due to the loss of feedforward information from the preceding vehicle, and thus the affected vehicle has to switch its control from CACC to adaptive cruise control (ACC) mode. In this study, we propose a novel platooning system with guaranteed stability and robustness against degradation due to communication disruption, in which the linear controllers of ACC and CACC modes are jointly formulated in a unified control framework. With such a proposed platooning system, a relatively small time gap is required for ensuring local and string stability of the two modes to enable robustness against degradation, compared with that of the state-of-the-art platooning systems. To expand the application in practical scenarios, we further develop the delay-robust controllers of ACC and CACC modes based on the delay compensating policy and Smith predictor to maintain better stability and robustness of the proposed platooning system with information delays. Moreover, the sufficient conditions of local stability and string stability in the frequency domain are derived based on the Routh-Hurwitz criterion and Laplace transform, respectively, for the proposed platooning system in normal and delay-robust ACC and CACC modes. Numerical experiments are conducted to demonstrate the mathematical proofs of stability analysis and the performance of the proposed platooning system on stability and safety aspects compared with the baseline platooning system.