Distributed adaptive sliding mode control strategy for vehicle-following systems with nonlinear acceleration uncertainties

This paper investigates the distributed adaptive control problems for nonlinear vehicle-following systems subject to nonlinear acceleration uncertainties involving vehicle acceleration disturbances, wind gusts, and parameter uncertainties. It is worth mentioning that the acceleration of the leader in most existing studies is always assumed to be zero or constant; the evolution of the leader in this paper may be subject to some unknown bounded input. Distributed adaptive control strategies based on an integral sliding mode control (ISMC) technique are proposed to maintain a rigid formation for a string of vehicle platoon in one dimension. First, distributed adaptive control based on traditional constant time headway (TCTH) policy under the assumption that the initial spacing and velocity errors are zero is developed to guarantee that all spacing errors are uniformly ultimately bounded and that the string stability of the whole vehicle platoon is also satisfied. Then, a modified constant time headway (MCTH) policy is proposed to remove the assumption of zero initial spacing and velocity errors and simultaneously effectively decrease the intervehicle spacing (i.e., increase the traffic density), making them nearly equal to those by using the constant spacing (CS) policy. Adaptive compensation terms without requiring a prior knowledge of upper bounds of the uncertainties are constructed to compensate for the time-variant effects caused by nonlinear acceleration uncertainties. Finally, numerical simulation results show the validity and advantages of the proposed policy up to a significant higher traffic density.