Research Of Cooperative Adaptive Cruise Control System Considering Input Saturation

With the development and application of intelligent transportation technology,adaptive cruise control is gradually developed and upgraded to cooperative adaptive cruise control(CACC).CACC utilizes V2 X communication technology to implement information interaction and cooperative cruise control of vehicular platoon.On the basis of ensuring safety,it shortens the following distance,reduces traffic energy consumption,and improves traffic safety and traffic efficiency.However,in the CACC system,there is a certain constraint range for the following error,relative velocity and acceleration.If the acceleration fluctuates backward along the platoon and violates the saturation constraint boundary,the acceleration of the following vehicle will continue to increase and the system will lose the string stability and cause traffic accident.Therefore,this paper takes the CACC system as the research object,establishes a mutually longitudinal kinematics model with input saturation(acceleration saturation),and studies the saturation control problem of the CACC system based on the parameter Lyapunov equation low gain design method,thereby effectively avoiding the saturation phenomenon of the system and improving the stability of the system.The main work of this paper is as follows:1.Considering the input saturation problem in the system,a mutually longitudinal kinematics model with saturation nonlinearity is established,and a saturation controller is designed based on a low-gain design method.At the same time,for the safety and comfort of the system,the linear quadratic optimal control is used to optimize the index to obtain the optimal solution.In order to verify the effectiveness of the control algorithm,homogeneous and heterogeneous platoon simulation is carried out in Simulink.The simulation results show that the proposed algorithm not only coordinates and optimizes the safety and comfort indexes,but also avoids the occurrence of system saturation and achieves the stability of the system.2.Aiming at the system uncertainty caused by the interference of communication and sensors in CACC system and the complexity of vehicle operation environment,a mutually longitudinal kinematics model with saturation nonlinearity and additive uncertainty is established.Based on the low gain design method and dynamic gain scheduling,robust saturation controller is designed to realize the robustness of the system under input saturation.In order to verify the effectiveness of the controller,homogeneous and heterogeneous platoon simulation is carried out in Simulink.The simulation results show that the robust saturation controller not only avoids the occurrence of input saturation,but also enhances the robustness of the system.3.In order to further verify the effectiveness of the designed controller,the layered control strategy of CACC system is adopted,in which the upper controller adopts the robust saturation controller.And in Simulink,the reverse dynamics model of driving/braking and the switching logic of driving/braking are built to get the lower controller.Secondly,the simulation test scene,information perception layer and vehicle dynamics model are built in PreScan.Then combined with PreScan and Simulink for joint simulation,the simulation results show that the robust saturation controller not only improves the safety and comfort of the system,but also achieves a good following effect.