Controller Design and Stabilization of Heterogeneous Vehicular Platoons under Time-Varying Communication and Actuator Delays

Cooperative Adaptive Cruise Control (CACC) enables safe, comfortable driving over short distances among multiple vehicles. One of the essential objectives of the CACC is to achieve vehicle stability in the presence of wireless communication throughout vehicles. Here, time delay is an unavoidable factor that must be accounted for to guarantee vehicle stability. This study presents a novel controller design for CACC systems to guarantee L_2-string stability under time-varying actuator and communication delays. Contrary to most existing work that assumes constant or identical delays, both types of delays are modeled as time-varying and heterogeneous across vehicles. The controller is synthesized using the Lyapunov-Krasovskii approach to handle varying delays effectively. Furthermore, a non-linear vehicle dynamics model is employed, and simulation studies are conducted for a heterogeneous platoon. The results demonstrate that the proposed controller ensures L_2-string stability for each vehicle in the heterogeneous platoon. A comparative analysis with two benchmark studies from the literature reveals that the proposed method requires larger headway-time constants, highlighting the trade-off between enhanced robustness and reduced traffic throughput.