| With the improvement of people’s living standards and the increasing number of motor vehicles,the problem of urban road traffic is becoming more and more serious.Intelligent transportation system provides the possibility to alleviate road congestion,increase traffic capacity,improve traffic efficiency,reduce environmental pollution and save energy.Connected vehicles system has become an important part of intelligent transportation system.However,for different vehicle communication structures and spacing policy between vehicles,choosing a reasonable controller structure,considering the reasons of parts wear,aging or external interference damage during the long-term operation of the vehicle,the design of feasible longitudinal vehicle’s platoon controller becomes the top priority.This thesis studies the longitudinal cooperative sliding mode control problem of the third-order connected vehicles system.The main work is summarized as follows:Firstly,the sliding mode control problem of connected vehicles system based on Lyapunov function is studied.Considering that the vehicle model is third-order(sliding mode control belonging to the high-order model),the PID sliding surface is designed by using the constant spacing policy between vehicles,and the Lyapunov function is designed according to the sliding surface and its first derivative.So Lyapunov second method is used to design Lyapunov sliding mode controller.It can realize the stability of single vehicle and the string stability of connected vehicles system.Finally,the digital simulation of the connected vehicles system composed of five vehicles is carried out and compared with the Lyapunov controller to verify the effectiveness and superiority of the proposed control algorithm.Secondly,the coupled sliding mode control problem of connected vehicles system with actuator failures and saturation is studied.A third-order nonlinear connected vehicles system model considering time-varying actuator faults,actuator saturation and lumped time-varying disturbances is established.Then,based on the established model,a new PID-type coupled sliding surface is designed,and a coupled sliding mode control algorithm combined with linear disturbance observer is proposed,and it was proved that the designed control algorithm could realize the stability of single vehicle and connected vehicles system.At the same time,in order to verify the effectiveness of the proposed control algorithm,numerical simulation is carried out on the connected vehicles system composed of five vehicles,and the comparison with the PID type connected vehicles system controller proves the superiority of the proposed controller.Finally,the controller is designed for the connected vehicles system with actuator failure and saturation.The third-order nonlinear dynamic model of the connected vehicles system with time-varying actuator failure and saturation is established.Based on the new model,a fuzzy adaptive sliding mode platoon controller combined with nonlinear disturbance observer is designed,which can simultaneously obtain the control objectives of single vehicle stability and string stability under zero initial spacing error.In addition,in order to solve the problem of vehicle string instability caused by non-zero initial conditions,a new improved constant time headway strategy is considered.Finally,numerical simulation and experiment are carried out on the connected vehicles system composed of simulation and Ackerman car to verify the superiority of the proposed control algorithm. |
