Robust Cooperative Adaptive Cruise Control System Design: Trade-Off Between Parasitic Actuation Lag and Communication Delay

In this paper, we provide a systematic procedure for designing cooperative adaptive cruise control (CACC) systems that are robust to parasitic actuation lag in braking and propulsion and delay in the communicated acceleration from the predecessor vehicle. In particular, we derive a tight lower bound on the employable time headway in CACC systems for guaranteeing robust string stability. The lower bound on the time headway is dependent on the upper bound on the parasitic actuation lag (τ₀) and the communication delay (ℓ). The main result of the paper is that if τ₀ exceeds ℓ, then the employable time headway is lower bounded by τ₀+ℓ. Otherwise, it is better to use adaptive cruise control (ACC) where the employable time headway is lower bounded by 2τ₀. The above results on CACC systems are then extended to next-generation CACC (CACC+) systems that employ information from multiple predecessor vehicles. Several comparative numerical simulations for a representative maneuver corroborate the main results.