  Vehicle-to-vehicle communications can be unreliable as interference causes
communication failures. Thereby, the information flow topology for a platoon of
Connected Autonomous Vehicles (CAVs) can vary dynamically. This limits existing
Cooperative Adaptive Cruise Control (CACC) strategies as most of them assume a
fixed information flow topology (IFT). To address this problem, we introduce a
CACC design that considers a dynamic information flow topology (CACC-DIFT) for
CAV platoons. An adaptive Proportional-Derivative (PD) controller under a
two-predecessor-following IFT is proposed to reduce the negative effects when
communication failures occur. The PD controller parameters are determined to
ensure the string stability of the platoon. Further, the designed controller
also factors the performance of individual vehicles. Hence, when communication
failure occurs, the system will switch to a certain type of CACC instead of
degenerating to adaptive cruise control, which improves the control performance
considerably. The effectiveness of the proposed CACC-DIFT is validated through
numerical experiments based on NGSIM field data. Results indicate that the
proposed CACC-DIFT design outperforms a CACC with a predetermined information
flow topology.
