Study On The Longitudinal Control System Of Vehicle Automatic Driving Via Simulation

The function of the Longitudinal Control System of Vehicle Automatic Driving is replacing driver to control the longitudinal motion of the vehicle by the automatic control technology.With the car ownership increased year by year,traffic jam and accident are caused frequently.This led to a reduction in the efficiency of travel,but a substantial increase in casualties.Longitudinal control system is one of the most important control system of intelligent vehicle,and it is an effective solution to solve the problems above.It responds to hazardous conditions faster,takes collision avoidance control more accurate and effective.This will maximize the avoidance of accidents and reduce casualties.Under the premise of driving safety,shorten the distance between the vehicles can effectively improve the efficiency of road traffic.Using the automatic driving control system instead of the driver to control the vehicle,it can relieve the fatigue of the driver,and also help to reduce the traffic accident caused by driving fatigue.This paper is based on Chongqing key industry common key technology innovation “The theme of the key technology of intelligent network of automobile industry common special”.The main research is the control strategy,and the following research has been carried out on the longitudinal control system of vehicle automatic driving.(1)The fuzzy control method has the advantage of not relying on the accurate system and can simulate the driver's control habits.Combined with the hierarchical control theory,this paper establishes a longitudinal control strategy based on the fuzzy theory.The fuzzy input of the system is the speed deviation and distance deviation,and the ideal acceleration is the fuzzy output.It can control the speed and the distance of the vehicle automatically.(2)On the basis of the above control strategy,through the analysis of the vehicle longitudinal driving conditions,a multi-mode switching control strategy is established.The control strategy can complete switching control of the cruise mode,approaching mode,following mode and avoiding collision mode,respectively,to achieve driving at the set speed,closing to the front car smoothly,following the front car safely and active collision avoidance.(3)In order to verify the effectiveness of the two kinds of control strategies,a simplified model of vehicle longitudinal dynamics is established in the MATLAB/Simulink software platform.Mainly includes,the engine model,the automatic transmission model,the brake system model,the drive system model,the reverse longitudinal dynamics model and the throttle/brake switch control model.(4)Common longitudinal driving conditions include: cruise condition,close to the front car condition,with the car driving condition and the collision avoidance condition.The simulation and analysis are carried out on the above four kinds of common longitudinal driving conditions,and the integrated driving condition.The results of the study show that: the established two kinds of control strategy can realize vehicle longitudinal autopilot.In addition,considering the safety and comfortable,multi-mode switching control strategy has better control effect.