String stability of heterogeneous leader-following vehicle platoons based on constant spacing policy

This paper is concerned with a leader-follower problem for a heterogeneous vehicle platoon subject to external bounded unknown acceleration disturbances. Distributed controller based on sliding mode control (SMC) approach are designed for the second-order follower-vehicles under the common assumption that the initial spacing and velocity errors are zero. The constant spacing policy known to have high traffic density and thus have high traffic flow is applied to design distributed controller. In addition, adaptive compensation technique is applied to compensate the time-varying effect of external disturbances. It is worth mentioning that the upper and lower bounds of the disturbances are not required to be known in advance. Furthermore, with the help of an explicitly constructed Lyapunov function, it is proved that the string stability of the vehicle platoon can be guaranteed. At the same time, the reduction of the chattering in sliding mode is achieved by introducing continuous function in control. Finally, a numerical example is given for illustration.