摘要
作为与轮胎直接接触的沥青路面,其抗滑性能是影响无人驾驶车辆制动安全性的直接因素.路面抗滑性能主要取决于路表纹理特征,建立考虑路表摩擦特性的无人驾驶制动模型是提高无人驾驶车辆制动安全性的有效方法.为了研究基于路表摩擦特性的无人驾驶车辆安全制动方法,考虑路表纹理抗滑贡献率计算了不同路面状态下峰值附着系数.基于无人驾驶车辆制动原理与沥青路面附着特性,采用CarSim/Simulink联合仿真建立了无人驾驶车辆制动模型,分析了直线正常制动、紧急制动及转弯行驶时无人驾驶车辆的制动特点,提出无人驾驶车辆在不同制动工况下安全制动限值.研究表明,不同行车速度下路面峰值附着系数呈凸型抛物线分布,随速度提高峰值附着系数逐渐减小.正常制动时,考虑乘客舒适性保持较小制动减速度;紧急制动时,雨天情况下制动距离比晴天平均增加45%左右,车距较大时建议以4~6 MPa制动力进行制动.无人驾驶车辆在潮湿或者干燥路面行驶过程应满足一定的安全车距,取晴天、雨天仿真安全制动距离平均值的1.1~1.2倍.随着弯道半径不断增大,不同路面状态下加速度干扰值基本上均减小,半径≥100 m时加速度干扰值下降率更为显著,为提高车辆制动舒适性弯道半径应控制在100 m以上.本研究提出了考虑路表纹理特性的无人驾驶车辆安全制动策略,可为无人驾驶车辆制动系统的理论设计及制动安全性评估提供参考.
Because of the direct contact between the tire and pavement,the skid resistance of asphalt pavement is a basic factor affecting the braking safety of autonomous vehicles.The road skid resistance mainly depends on the texture characteristics of the road surface.Considering the pavement friction characteristics,building a braking model of autonomous vehicles is an effective method to improve the braking safety of autonomous vehicles.In order to develop the safety braking method for autonomous vehicles based on the road surface friction characteristic,an automatic close-range photogrammetry system(ACRP system)was proposed and built based on the circle arranged three cameras close-range photogrammetry(CRP)technology to obtain the asphalt pavement surface texture accurately in real time.Automatic image acquisition and 3D reconstruction were achieved by the ACPR system.Sand patch testing method and laser scanning method(ZGScan)were applied to collect the on-site asphalt pavement texture comparing with the results of ACRP system.It shows the texture data obtained by ACPR system have relatively high accuracy and efficiency with recognition accuracy close to 0.02 mm.Then,the peak adhesion coefficients under different road conditions were calculated by considering the skid resistance contribution of the road surface texture.Based on Car Sim/Simulink joint simulation,a braking model for autonomous vehicles was established.The characteristics of the autonomous vehicles during straight normal braking,emergency braking and driving on curved sections were analyzed.Then,the safety braking distance under different conditions was put forward.The research shows that the variation trends of friction coefficient curves under different pavement conditions(dry and wet pavement)are basically the same,which both decrease significantly with the increase of relative slipping ratio.When the speed exceeds 40 km/h,the curve tends to be gentle,indicating that the actual contact area of the tire-road comes to a stable status when the speed is relatively high.Based on the tire hydroplaning model built by ABAQUS,the peak adhesion coefficient curves for different pavement conditions were obtained.It can be seen that the peak adhesion coefficient of the road surface is convex parabolic distribution at different driving speeds.Moreover,the peak adhesion coefficient gradually decreases as the speed increases.During normal braking,the vehicle should keep relatively low braking deceleration considering passenger comfort.As for emergency braking,autonomous vehicle should be equipped with professional short-range radar,long-range radar and high-definition camera to detect the environment surrounding the vehicle.On rainy days,the braking distance is averagely increased by about 45%compared to sunny days.When the braking distance between vehicles is large enough,it is recommended to brake with a braking force of 4-6 MPa.Autonomous vehicles should keep a certain safe distance,which requires 1.1-1.2 times of the simulated average value of safety braking distance during the driving process on dry or wet pavement.As the radius of curved sections increases,the acceleration interference values under different road conditions basically reduce.When the radius is greater than or equal to 100 m,the decrease rate of the acceleration interference value is more significant.In order to improve the braking comfort of the vehicles,the radius of the curved road should be controlled above 100 m.In this paper,the safety strategies for autonomous vehicles considering pavement surface texture characteristics can provide references for the theoretical design of braking system and braking safety evaluation for autonomous vehicles.
作者
黄晓明
蒋永茂
郑彬双
赵润民
Xiaoming Huang;Yongmao Jiang;Binshuang Zheng;Runmin Zhao(School of Transportation,Southeast University,Nanjing 211189,China)
出处
《科学通报》
EI
CAS
CSCD
北大核心
2020年第30期3328-3341,共14页
Chinese Science Bulletin
基金
国家自然科学基金(51778139)
江苏省研究生科研与实践创新计划(KYCX18_0146)资助
关键词
无人驾驶车辆
沥青路面
路表摩擦特性
峰值附着系数
制动安全性
autonomous vehicles
asphalt pavement
road surface friction characteristic
peak adhesion coefficient
braking safety
作者简介
联系人:黄晓明,E-mail:huangxm@seu.edu.cn
