Robustness of String Stability to Delay Mismatch and Safety of CTH Predictor-Feedback CACC

Abstract

For the predictor-feedback Cooperative Adaptive Cruise Control (CACC) design for homogenous platoons, recently developed by Davis, we establish robustness of string stability to delay mismatch and positivity of spacing and speed states. Each individual vehicle’s dynamics are described by a second-order linear system with delayed desired acceleration, under acceleration information transmitted to the ego vehicle from a single, preceding vehicle. The nominal design (in the delay-free case) is a constant time-headway (CTH) policy and no restriction on the delay size, in relation with the desired time headway, is imposed. The proofs rely on combination of an input-output approach (on the frequency domain) and on deriving estimates on explicit, closed-loop solutions; under specific, sufficient conditions that are derived on initial conditions and parameters of the baseline, CTH controller.