Collaborative Adaptive Cruise Control Fleet Simulation Research

As the concept of advanced driver assistance system(ADAS)is put forward and its related content is continuously improved and developed,its significance and value are increasingly recognized by people.It is believed that ADAS can solve some practical traffic problems and provide convenience for people's lives.As a branch of ADAS,with the help of dedicated short-range communication technology DSRC and LTE-V2 X data communication technology,the cooperative adaptive cruise control system CACC(Cooperative Adaptive Cruise Control)began to develop.The system can interact with the surrounding traffic environment through the vehicle-road communication system to obtain real-time driving information of vehicles and surrounding vehicles,so as to make judgments based on actual traffic conditions,and then control vehicles to complete driving tasks.Compared with fixed-speed cruise and ACC systems,CACC system emphasizes the driving of cooperative queues,which can improve the safety,smoothness and comfort of vehicle driving,and can quickly respond to the sudden situation during vehicle driving.The improvement of the system's traffic efficiency helps.Therefore,the research and exploration of the CACC system has important theoretical and practical significance.The CACC system is developed on the basis of the adaptive cruise system(ACC).As an emerging concept and technology,the system is still in the research and experimental stage.Although there have been certain achievements and conclusio ns about the basic structure,operation mode and control strategy of the CACC system,for one of the main characteristics of the CACC system-collaborative queue driving,there is little research content.During the driving process of the CACC fleet There is no clear understanding and conclusion about the performance,driving laws and characterist ics of the car.Therefore,this article takes collaborative adaptive cruise control fleet as the research object to explore and analyze related content.This article first gives an overview analysis and summary of the related technologies,system composition,and system of the cooperative adaptive cruise control system.Mathematical modeling of vehicle formations and selecting fixed workshop time interval strategy as the basic strategy of vehicle formation interva l control.Then use the idea of hierarchical control to achieve the vehicle queue control goal,and then model the entire control system.The model system constructed can be divided into an upper-level acceleration decision layer and a lower-level vehicle control layer.The design of the upper-level expected acceleration decision-making layer adopts the classic modified IDM vehicle following model.In view of the lack of consideratio n of the road driving environment conditions of the IDM model,the vehicle is subjected to stress analysis,mainly considering the influence of various resistances,and improving the IDM model.The improved IDM model comprehensively considers the influencing factors of road driving environment conditions,and is closer to the road and driving environment conditions encountered in the actual driving process,so that the expected acceleration it obtains is more reasonable and accurate.The parameter impact analysis of the entire upper-level acceleration decision-making model is carried out,and the influence degree of vehicle spacing,front-vehicle acceleration and head-vehicle acceleration on acceleration decision-making is summarized and analyzed.The results show that the vehicle spacing is the main influencing factor for the driving safety and stability of the fleet.When the vehicle spacing gradually approaches the safe distance,the influence of the acceleration of the preceding vehicle and the acceleration of the head vehicle on the driving of the fleet begins to gradually increase.In the design process of the lower-level controller,it is necessary to use the vehicle dynamics to analyze the force of the vehicle in the driving state to obtain the influe nce of the vehicle force on the vehicle state.Then,the contrast table method is used to construct the model of the vehicle drive system controller and the brake system controller: the engine model is established by back-checking the vehicle engine torque characteristic MAP map,and it is normalized to obtain the throttle opening degree.Normalized function;the brake system model is established by back-checking the braking characteristic MAP map,and then the modeling of the entire control system is completed.Finally,the Prescan simulation software was used to build a simulation experime nt platform.The simulation experiment scene was built with this software,and the experimental vehicle carrying radar sensors and V2 X communication equipment was combined with Matlab / Simulink software to carry the CACC system model constructed in this paper.Experimental vehicles and vehicle formation.Simula t io n experiments under four typical working conditions were performed on this platform,namely starting acceleration and deceleration conditions,high-speed emergency braking conditions,alternate acceleration and deceleration conditions,and communication delay conditions.The focus is on vehicle distance.The influence of vehicle acceleration and head vehicle acceleration on the safety and stability of CACC fleet,and summarize the driving law of CACC fleet.The results of simulation experiments show that when the vehicle distance does not meet the requirements of the safety distance,the vehicle distance is the main factor affecting the safety and stability of the vehicle fleet.The impact of driving has begun to increase.Considering the two CACC systems,the distance between vehicles can be reduced,and the driving stability and driving comfort of the fleet can be enhanced.In addition,V2 X communication delay will increase the following distance and reduce the stability of the team.