Research On Rutting Threshold Of Asphalt Pavement For Autonomous Vehicle Condition

With the rapid development of driverless technology around the world,the unmanned driving of vehicles has also put forward higher requirements for road engineering.Rutting is one of the common phenomena of asphalt pavement.The decrease in road surface smoothness caused by rutting has a certain impact on the driving stability and safety of the vehicle.At present,the rutting of asphalt roads in all countries in the world adopts a single rut depth to control,and the special needs of autonomous vehicles to be distinguished from traditional manned vehicles are not considered.This will have a certain negative impact on the safe operation of autonomous vehicles.Based on the driving characteristics of driverless vehicles,this paper studies the threshold of asphalt pavement rutting for autonomous vehicles.First,use MATLAB to perform unit standardization,grid thinning,pavement model solidification,and file mirroring on the pavement texture information obtained with 3D close-range photography technology,so that it can form an inp model file that can meet the requirements of Abaqus calculations.Then the Yeoh model is adopted to build a two-dimensional finite element model of the 185R13 LT tire,and a complete three-dimensional tire model is formed by rotation.The static state analysis is used to calculate the inflation of tire and contact between tire and road,the steady state analysis is used to calculate the tire rolling under dry conditions;and the explicit analysis is used to conduct the three-term coupling of tire,pavement and Euler fluid grid cells to obtain the final tire-pavement-water flow three-coupled operation results.The model is validated through the static grounding state of the tire and the calculation results of dynamic water skiing.The results show that the finite element model established by this method can well characterize the rolling of vehicle tires under the condition of wet road surface,and the curve of friction coefficient on AC-13 pavement is concluded.Secondly,considering the characteristics of robustness,simplicity,etc.,this paper uses the fuzzy control of the autonomous vehicle lane change control system as the application object.In Simulink,a triangular membership function is used in fuzzy control.The vehicle deviation angle,body offset,and the distance between the center of mass of the vehicle body and the target point is used as the fuzzy control control parameter,and the virtual steering wheel angle of the vehicle is used as the output control object.Through the 7 fuzzy control subsets and 35 fuzzy control rules,the autonomous vehicle during the lane change process is realized.The direction is self-controlled,and the limit control steering rate under the unmanned condition is determined based on the standard that the vehicle body does not intrude into the third lane.This article divides the rut shape into three indexes: rut depth,rut side angle,and rut width.The stability of the body affected by the rut is divided into two indexes: vehicle body roll angle and vehicle body vertical acceleration.Through orthogonal design and Simulink-Carsim joint simulation,the sensitivity of the three indicators of rut shape to different indicators of body stability was obtained,and different rut shape control standards for dry conditions were proposed based on different body stability indicators.This paper further uses simulation calculations to obtain the minimum friction coefficient requirements for the safety guarantee of the vehicle’s lane change under autonomous control.Combined with the results of finite element calculations,a rutting threshold for autonomous vehicles under wet road conditions is further proposed.The results show that as the speed increases and the thickness of the water film increases,the friction between the tire road surface and the corresponding friction coefficient decreases monotonously;the rut depth has a greater impact on the roll angle of the vehicle body,and both the rut depth and the rut side angle have a greater impact on the vertical acceleration of the vehicle body.The rut width has little effect on both the roll angle and the vertical acceleration of the vehicle body,so it can be ignored.When considering the index of the body roll angle,the rutting threshold control value is 2.5cm of rut depth,the rut width and The rut side angle does not need to be controlled;when considering the maximum vertical acceleration index of autonomous vehicles,the rut depth should generally not be greater than 1.5cm,and when the rut depth reaches 20 mm,the rut side angle should not be greater than 1°.Under wet conditions,the speed should be controlled below 70 km / h,and the rut depth should not exceed 10mm;when the vehicle speed is 60 km / h or less,the rutting threshold can be further relaxed.