Padé approximation of delays in CACC-controlled string-stable platoons

Cooperative Adaptive Cruise Control (CACC) improves road throughput by employing inter-vehicle wireless communications. The inherent communication time delay significantly limits the minimum intervehicle distance in view of string stability. Applying a Padé approximation leads to a model with a rational transfer function, which allows many control methods to compensate for this delay to a certain extent. Our objective is to find the lowest possible order of Padé approximations, which is sufficiently accurate in view of string stability. To this end, the minimum string-stable time gaps are chosen as the main criterion against which the quality of the Padé approximations is measured. The results indicate that it is feasible to apply a 2nd-order Padé approximation in the given CACC system