Research On Full Speed ACC Control Algorithm Based On Different Road Adhesion Coefficient

In recent years,intelligent vehicles have developed rapidly.As one of the main components of intelligent assisted driving(ADAS),the full-speed adaptive cruise system(ACC)is of great significance for improving driving safety and improving occupant comfort.However,the current mainstream full-speed ACC system is greatly affected by the environment and has poor adaptability to different road conditions.,so this paper studies the full-speed ACC system based on different road adhesion coefficients.Aiming at the road adhesion coefficient estimation algorithm,this paper first builds a vehicle dynamics model based on reasonable assumptions,calculates the relevant state parameters of the vehicle,and proposes the recursive least square method and the road similarity recognition method.The recursive least square method is used when the wheel slip ratio is large;The road similarity recognition method is selected when the wheel slip ratio is small.According to the difference of wheel slip ratio,the two algorithms can be used flexibly.The effect of the adhesion coefficient estimation method is verified by the simulation of three different roads: ice,wet and dry.Aiming at the full-speed ACC system,this paper divides it into the upper-level control logic and the lower-level execution algorithm.For the upper-level control algorithm,this paper researches and designs the human-computer interaction module,the full-speed ACC followup target screening module,the signal board intelligent speed limit module,the cruise control module and following cruise module.This paper elaborated the function realization process of each module in detail.The main algorithms used include hazardous area definition,PI control,decay exponential function,model predictive control and effective set method.The model predictive control algorithm obtains the estimated value of the road adhesion coefficient,and carries out the boundary constraint planning for the expected acceleration of the subjective vehicle.After the model is built,simulation tests are carried out for five working conditions:cruise control,signal speed limit,steady-state following,sidecar cut-in and exit,and stop-start to verify the superiority of the algorithm.Aiming at the lower actuator part of the full-speed ACC,this paper analyzes the driving force and resistance force balance of the main vehicle to obtain the engine torque value to realize the main vehicle drive control.For brake control,this paper designs a torque balance feedforward model,deceleration error feedback model,and the HCU actuator model to simulate the working state of the ABS wheel cylinder.By obtaining the speed-acceleration curve of the actual vehicle under no load,design the actuator drive/brake switching logic module.In order to prevent the frequent switching of the driving and braking process,this paper calibrates the switching buffer based on the actual vehicle data of Dongfeng AX7.Finally,this paper compare the actual vehicle ESC through experiments to verify the functional effect of the actuator.This paper uses a hardware-in-the-loop simulation test bench to verify the algorithm’s excellence.This paper set real vehicle vehicle dynamics parameters in VI-Car Real Time,build driving scenes and traffic vehicle operating rules in SCANe R,and use the hardware-in-theloop simulation platform of the research group.Aiming at constant speed cruise,signal board intelligent speed limit,steady-state car following,target vehicle cut-in and cut-out and followstop-start five working conditions,this paper conducts comparative experiment respectively on the high-attachment road,the low-attached road,and whether there is a road adhesion coefficient estimator.The results show that full-speed ACC can adapt well to different road attachment conditions.