ESO-based adaptive hierarchical control for heterogeneous vehicles platoon with time headway policy and input delay

This paper investigates the adaptive hierarchical tracking control problem for heterogeneous vehicles platoon subject to model uncertainties and input delay. A hierarchical control architecture is constructed, with separate controllers designed for the leader and followers to enhance the robustness of the system. Based on this framework, a modified constant time headway policy is proposed to address excessive transient response caused by nonzero initial spacing between vehicles. Specifically, by introducing a compensation signal, this policy eliminates the zero-velocity assumption and initial spacing issues while reducing inter-vehicle spacing, ensuring rapid convergence to a stable platoon even in the presence of initial errors. Moreover, an extended state observer (ESO) is employed to approximate and compensate the uncertainties for the system, and Pade approximation approach is utilized to avoid input delay. Lyapunov stability analysis demonstrates the internal stability and string stability of the closed-loop system. Simulation examples and comparative results validate the reliability of the control scheme.