Distributed Sliding Mode Control Of Vehicle Platoon System

In recent years,with the development of autonomous driving technology,intelligent transportation systems have attracted extensive attention.As an important research of intelligent transportation systems,vehicle platoon is beneficial to alleviate road congestion,enhance road safety.It can also reduce traffic accidents and environmental pollution effectively.The main purpose of vehicle platoon control is to make vehicles maintain a certain expected distance and the same velocity under the condition of safe driving through vehicle-to-vehicle communication and platoon control algorithms.Sliding mode control is widely used in the control of vehicle platoon due to its strong robustness to uncertain disturbances.The traditional sliding mode control only guarantees the asymptotically stable of the system due to its linear sliding mode surface.At present,both finitetime and fixed-time sliding mode control are research hotspots,and their convergence speed and performance are better than traditional sliding mode control.Because of the need to ensure internal stability and string stability at the same time,it makes the research of combining vehicle platoon control with sliding mode control significant and worthful.Therefore,for vehicle platoon and its distributed characteristics,this paper proposes finite-time and fixed-time vehicle platoon distributed control algorithms to ensure the vehicle stability and string stability.The main contents are as follows:(1)For the second-order vehicle platoon,it investigates the problems of internal stability and string stability under the constant time headway policy and bidirectional information topological flow.The traditional linear sliding mode surface cannot make the system converge in a finite time.A coupled dynamic integral sliding mode distributed control is proposed,so that vehicle spacing error can converge to zero within a finite time.Based on the coupled sliding mode surface,the algorithm eliminates the chattering phenomenon caused by the sign function in the sliding mode reaching law through dynamic integration,and improves the convergence speed of vehicle spacing error.(2)For a second-order vehicle platoon with prescribed performance constraints,the fixedtime stability problem with nonlinear spacing strategies is studied.Considering the instantaneous performance of the system,a prescribed performance function is designed to constrain the range of inter-vehicle distance error during the convergence process.The convergence time of finite-time control is related to the initial state value of the system,while the fixed-time control’s convergence time has nothing to do with the initial state value,which can more conveniently determine the specific convergence time of the system.Therefore,a new integral terminal sliding mode surface is proposed,and a distributed sliding mode control algorithm combining power reaching law and smooth function is used to reduce the chattering phenomenon of the controller.Furthermore,the vehicle spacing error converges to zero in a fixed time.(3)The problem of fixed-time stability with external uncertain disturbances under thirdorder vehicle platoon is investigated.By using the acceleration information of the vehicle,a fixed-time disturbance observer is designed to estimate the external uncertain disturbance of the system,and its estimated value is introduced into the feedforward term of the controller for disturbance compensation.Secondly,considering the nonzero initial error,a modified constant time headway strategy is proposed to overcome the influence of the nonzero initial error on the vehicle controller.In addition,a new terminal sliding mode surface is introduced to avoid the nonsingular problem existing in the three-order system.Furthermore,a nonsingular fixed-time terminal sliding mode control algorithm is proposed to ensure that the vehicle spacing error converges to zero in a fixed time.