String Stability Analysis of Connected Vehicular Systems Based on Car-Following Model

String stability analysis is one of key factors to understanding traffic flow dynamics. Cooperative adaptive cruise control (CACC) vehicles are desired to enhance stability of vehicular flow by monitoring multiple vehicles. From the perspective of mixed traffic, this study proposes a generalized analysis method for CACC feedback gains to achieve stable mixed flow. To deal with this, a random mixed flow is divided into general small platoons, in which one tail CACC monitors multiple vehicles ahead. These general platoons with different lengths are defined as connected vehicular systems. Based on the generalized car-following models, transfer function theory is employed to derive string stability criteria that can keep these connected vehicular systems stable for all possible vehicle speeds. A case study is also carried out to validate usability of the proposed generalized work. The proposed generalized method is applicable to various car-following models and large connected vehicular systems, thereby helping achieving the string stability enhancement of mixed traffic flow.