Energy-Based Analysis of String Stability in Heterogeneous Platoons

Analysis of string stability in vehicle platoons has mainly been confined to strings of vehicles having similar dynamics. In this scenario, errors propagate uniformly downstream in the string, making string stability analysis convenient. In real driving and platooning scenarios, homogeneity of vehicles is highly unlikely. This means errors amplify/attenuate in a nonuniform manner downstream, as a result of differing dynamics of the current and preceding vehicles appearing in the platoon error dynamic model. This complicates string stability analysis. To remedy this issue, a dynamic proxy to decouple the error dynamics of current vehicle from its predecessor is proposed. Then, by utilizing passivity-based techniques to constrain the output strict passivity index of each vehicle subsystem in the string to unity through a two-stage control strategy, the condition for string stability is met. Validation of the proposed strategy through numerical simulations is nresented.