Finite time observer-based super-twisting sliding mode control for vehicle platoons with guaranteed strong string stability

This paper presents a finite time disturbance observer (FTDO)-based super-twisting sliding mode control (SMC) structure for a vehicle platoon system with a focus on parameter uncertainties as well as external disturbances. In order to compensate the parameter uncertainties and external disturbances, a composite FTDO-based super twisting SMC method is developed under zero initial spacing deviations, where the parameter uncertainties, external disturbances, and the preceding vehicle's acceleration are estimated as a lumped disturbance by employing an FTDO. Benefiting from the FTDO, the estimation error dynamics is stable in finite time. Different from the existing SMC-based achievements, the continuity of the control signals can be achieved, which avoids the undesirable chattering phenomenon in the existing SMC-based works. Leveraging an FTDO, the preceding vehicle's acceleration information is not required, which enables the proposed control method to exploit a unidirectional information flow topology. Thus, it can reduce communication burden compared with bidirectional information flow topologies. Then, an improved time gap policy is employed to extend the developed control scheme to a more general case with nonzero initial spacing deviations. In addition, the individual stability of each vehicle is rigorously analyzed by resorting to the Lyapunov stability theory. Furthermore, the strong string stability of the whole vehicle platoon is derived with the help of the Laplace transform. Finally, numerical simulations are conducted to illustrate the effectiveness and applicability of the developed control scheme.