Sliding-mode control for heterogeneous vehicular platoons with unknown matched and mismatched disturbances under intermittent communications

In this work, we investigate a longitudinal platooning control problem of heterogeneous vehicles with a focus on external unknown disturbances, parameter uncertainties and intermittent communications. When vehicle platooning encounter intermittent communications, the performance of the platooning will be degraded. Nevertheless, the existing researches can not deal with the aforementioned three issues effectively. To this end, a novel nonsingular dynamic terminal sliding-mode control (NDTSMC) law is contrived. First, for a heterogeneous cooperative adaptive cruise control (CACC) or adaptive cruise control (ACC) platooning system of mixed vehicles, a hybrid mathematical reference model is developed. Then, we propose a CACC-ACC switched approach which activates either a CACC mode or an enhanced ACC mode relied on communication reliability. The unknown disturbances and parameter uncertainties can be together served as a unknown lumped matched (or mismatched) disturbance, depending on the circumstances. The unknown lumped matched (or mismatched) disturbance can be estimated by a finite-time disturbance observer (FTDO). Based on the observation, a novel switched controller consisting of a baseline controller part and an observation-based NDTSMC law part is proposed. Furthermore, combined with Lyapunov stability theory, it can be demonstrated that the stability of the string of mixed vehicles in the heterogeneous platoon can be robustly guaranteed after switching. Simulation examples show that the proposed approach exhibits satisfactory control properties for addressing intermittent communications. The convincing performances for attenuating parameter uncertainties and external unknown disturbances are achieved, which are also shown in simulations.