Fast and Smooth Trajectory Planning and Control for Vehicle Platoons During Cut-In Maneuvers

Fast and smooth cut-in maneuvers in vehicle platoons are challenging due to abrupt structural changes that induce reference discontinuities and downstream disturbance propagation. From a theoretical perspective, existing string stability formulations do not explicitly account for reference discontinuities caused by cut-in-induced platoon reordering. To address this gap, a novel definition of local string stability is introduced and formally proven, ensuring local spacing regulation and attenuation of reference-induced disturbances within downstream sub-platoons. Building on this theoretical foundation, this paper proposes a three-stage framework that integrates offline pre-planning, traffic-aware online re-planning, and distributed MPC to accommodate time-varying traffic conditions while preserving local string stability during cut-in maneuvers. A hybrid reference tracking strategy with adaptive weighting is designed to enable fast and smooth trajectory transitions during cut-in maneuvers. Simulation results demonstrate the effectiveness of the proposed method in terms of maneuver execution quality and convergence performance under representative cut-in scenarios.