无人驾驶汽车作为未来交通的发展趋势,相比传统有人驾驶车辆具有减少交通事故、缓解交通压力等优点,但其制动模式与传统有人驾驶相比存在很大差异。传统驾驶车辆依赖驾驶员的判断采取适合的制动措施,而无人驾驶汽车制动措施主要依赖车-路协同的经验模型,忽略了不同路面状态下纹理特性的影响。实际上,路面的纹理特性与路面抗滑性能存在直接联系,良好的路面抗滑性能能够为高速行驶的车辆提供充足的摩擦力,保证车辆行驶过程中的安全性。而且,汽车制动时轮胎与路面的相互接触作用直接影响车辆制动性能,尤其是在潮湿路面。为了达到最大制动效能,传统的ABS制动机理主要是将轮胎滑移率控制在最佳区域（15～20%范围内）,忽视了汽车动力学强非线性、车辆制动系统差异性及路面附着特性不确定性,无法适应路面抗滑性能的变化。鉴于此,结合无人驾驶车辆的技术特性及路面抗滑机理,论文首先利用ABAQUS分析了胎/路相互作用下沥青路面的抗滑特性。然后,基于Car Sim/Simulink联合仿真研究了无人驾驶车辆在不同制动场景中制动稳定性及对沥青路面抗滑性的感应需求,从而建立了考虑行车舒适性的无人驾驶制动过程中沥青路面抗滑评价体系。鉴于橡胶轮胎与粗糙路表的摩擦机理,对比分析了典型沥青路面摩擦系数预测模型,选取Persson粘滞摩擦理论进行后续动摩擦系数计算。然后,基于近景摄影测量原理搭建的自动化近景摄影测量系统（ACRP系统）实现沥青路面表面纹理图像实时自动采集并重构三维沥青纹理路面,提取路表三维高程点坐标数据,并采用MATLAB编程获取不同路面条件的功率谱密度曲线,进一步采用Persson摩擦模型计算得到不同路面状态下的动摩擦系数。干燥与潮湿条件下三种沥青路面的摩擦系数曲线变化趋势基本一致,均随着行驶速度的增大轮胎与路面之间的摩擦系数逐渐降低,在0km/h至10km/h内摩擦系数值呈线性显著降低。当速度超过40km/h时,摩擦系数曲线趋于平缓,表明较大速度下主要由滞后力提供摩擦力。通过现场DFT试验验证了理论值的准确性,然后建立符合实际的路面摩擦系数数据库从而为无人驾驶车辆的准确制动行为提供抗滑参数。随着车辆行驶速度提高,轮胎与路面之间附着力急剧下降,导致制动过程中轮胎常发生滑移现象。而且,无人驾驶车辆与传统车辆在制动特性、感应需求方面存在显著差异。因此,结合ACRP系统实时识别的路表纹理信息数据,基于耦合欧拉-拉格朗日法（CEL法）采用ABAQUS有限元程序建立表征纹理的沥青路面与轮胎的接触有限元模型。考虑路面分形特性研究了轮胎-沥青路面的相互作用机理,分析了路面附着特性在不同影响因素下的变化规律;并根据正交试验设计原理确定无人驾驶车辆路面纹理实时识别需求的显著影响参数,仿真分析得到干燥条件上路面峰值系数附着系数变化曲线。基于建立的轮胎-路面接触模型导入欧拉流体模型,采用CEL法建立轮胎-路面-水流三相耦合作用有限元模型,并根据美国NASA经验公式验证滑水模型准确性,回归分析得到轮胎临界滑水速度数学模型。基于已建立的三相耦合模型,考虑不同类型沥青路面水膜厚度的影响因素（行车速度、宏观纹理参数及降雨量等）,模拟得到潮湿路面上沥青路面纵向附着力,分析了不同路面水膜变化情况对沥青路面附着系数的影响规律;采用正交试验设计理论分析了潮湿路面最显著影响因素,仿真得到潮湿条件下不同沥青路面类型的胎/路峰值附着系数随速度变化曲线。在获取路面峰值附着系数的基础上,根据无人驾驶车辆制动特点分析无人驾驶车辆制动过程对路面信息的感知需求,基于路面附着特性对车辆制动行为的影响进行无人驾驶车辆制动系统的建立。考虑制动过程中车辆动力学的强非线性,推导出基于路面峰值附着特性车辆达到的期望制动压力计算公式。然后,采用MATLAB/Simulink模块进行无人驾驶车辆逆制动模型的搭建。进一步,根据Car Sim软件中提供的整车模型参数,采用Car Sim/Simulink联合仿真进行无人驾驶车辆制动性能仿真分析,并与传统ABS系统对比进行验证所建立无人驾驶车辆制动模型的有效性。基于建立的无人驾驶车辆制动模型与转向控制算法,采用Car Sim/Simulink联合仿真建立无人驾驶车辆行驶的动力学模型。考虑直线道路上正常制动与紧急制动、曲线（曲线-超高）转向制动及斜坡道路制动等情况下无人驾驶车辆的行驶特点,选择制动减速度、横向偏移距离及制动距离作为制动性能评价指标进行分析路面感应需求参数对车辆制动稳定性的影响规律。然后,采用正交试验设计理论分析感应需求参数对车辆制动稳定性的影响程度。基于路面实时附着特性,确定无人驾驶车辆在典型制动场景及不同路况下的制动策略。舒适性是体现无人驾驶车辆制动性能优势的关键,基于国际标准ISO简化了以加权加速度为变量的行驶舒适性指标计算模型,并进行舒适度评价等级划分。根据不同制动场景下无人驾驶车辆制动特点,分析采集的车辆速度变化特征并进行加权加速度计算,得到各种制动情况的舒适性指标数据。采用Logistic回归理论建立了不同场景下无人驾驶车辆制动舒适度评价模型,分析不同场景下制动舒适性的变化规律及对道路环境参数的需求,提出了不同道路行驶环境下无人驾驶车辆提高舒适性的对应策略。基于舒适性评价方法建立了一种无人驾驶车辆制动舒适性评价体系,可为未来无人驾驶车辆在复杂道路环境中安全制动、感知系统的精确识别提供理论指导。

To highlight the advantages of autonomous vehicles (AVs) in modern traffic, it is necessary to investigate the sensing requirement parameters of the road environment during the vehicle braking process. Based on the texture information obtained using a field measurement, the braking model of an AV was built in Simulink and the ride comfort under typical braking scenarios was analyzed using CarSim/Simulink co-simulation. The results showed that the proposed brake system for the AV displayed a better performance than the traditional ABS when considering pavement adhesion characteristics. The braking pressure should be controlled to within the range of 4 MPa similar to 6 MPa on a dry road, while in wet road conditions, the pressure should be within 3 MPa similar to 4 MPa. When steering braking in dry road conditions, the duration of the "curve balance state" increased by about 57.14% compared with wet road conditions and the recommended curve radius was about 100 m. The slope gradient had a significant effect on the initial braking speed and comfort level. Overall, the ride comfort evaluation method was proposed to provide theoretical guidance for AV braking strategies, which can help to complement existing practices for road condition assessment.

为改善路面结构抗反射裂缝能力,提升沥青路面材料循环利用率,将复合改性橡胶沥青与路面循环利用技术综合运用于应力吸收层中,设计制备了复合改性橡胶沥青再生混合料AC-10。通过沥青胶结料试验研究比较了复合改性橡胶沥青、SBS改性沥青、

A new method, the notched specimen cracking test (NSCT), is presented to directly measure the thermal stress and critical temperature of asphalt binders at low temperatures. The NSCT contains a notched specimen that contraction deformation is limited by special invar steel fixtures exposed to a continuous cooling temperature field provided by a programable environmental chamber. To simulate the actual thermal contraction state-strain level of asphalt pavement in the laboratory, the geometry of the binder specimen was carefully designed by theoretical computation based on the superposition principle. The preliminary test result shows that NSCT for evaluation of the potential cracking risk of modified or non-modified binders at low temperatures is reliable and easy to operate. The coefficient of variations of thermal stress results is at least 50% smaller than the traditional thermal cracking measurement method.

轮胎与路面间的附着特性是影响车辆行驶安全性的最重要因素之一.雨天条件下沥青路面容易产生水膜,由于流体动力润滑作用使得轮胎相对于粗糙路面发生了一定距离的滑移,产生滑水现象,在很大程度上影响胎路之间的附着特性.根据雨天情况下

As the main objective influencing factor on the brake safety of autonomous vehicles, pavement texture information is directly related to road surface antiskid performance. However, in the brake system of autonomous vehicles, the influence of road surface adhesion characteristics on braking stability is seldomly considered. To study the braking stability of autonomous vehicles on curved sections under different road conditions, the advanced close-range photogrammetry system was utilized to extract the road surface texture information. Thereafter, the power spectral density (PSD) of the road surface was calculated by MATLAB to obtain the pavement adhesion coefficient curves based on the Persson friction theory model under different road conditions. Considering the pavement adhesion characteristics, the braking model of autonomous vehicles was built in Simulink, and then, the braking performance on curved sections was analyzed with CarSim/Simulink cosimulation. The results indicate that, according to the adhesion coefficient of different asphalt pavement types under different road conditions, the ranking order is open-grade friction course (OGFC) > stone matrix asphalt (SMA) > dense-graded asphalt concrete (AC). In addition, both the maximum lateral offset distances and the maximum lateral forces of the tires decrease as the curve radius gradually increases under different road conditions. It can also be found that there is a relatively uniform vertical forces distribution of the tire when the curve radius is no less than 100 m, and the limit speed of the vehicle varies parabolically with increasing in curve radius. Compared with dry road, the reduction of vehicle braking deceleration is more significant and the yaw rate is greater on wet road. Last but not least, the braking comfort with a radius of 200 m is the best according to the comfort index (CI) in International Standard ISO, in which the comfort level can be sorted into six levels.

为合理表征沥青混合料的细观特性，并深入研究沥青混合料低温开裂过程中温度应力积累和裂缝扩展的细观机理，基于离散元程序PFC2D建立沥青混合料约束试件温度应力（TSRST）模拟试验方法。根据逆向体视学原理和概率论方法，引入沥青混合料三维体积级配与二维数量级配的转化关系，建立二维离散元虚拟试件；结合沥青混合料各组分之间的接触行为特点，赋予不同的接触本构模型，借助室内试验测定集料和沥青砂浆的宏观参数，推导得到不同温度下各相材料间的细观接触参数；通过TSRST模拟试验，分析试件内部温度场变化规律、温度应力曲线、细观接触力的分布特征以及低温开裂的细观机理。研究结果表明：TSRST离散元模拟和室内试验的结果具有较高的吻合度，断裂温度相对误差为3.7%,断裂强度相对误差为4.8%,TSRST模拟试验具有较高的准确性，能够作为试件低温抗裂性评价的可靠方法；试件的破坏可以分为3个阶段：（1）起裂阶段，在转化点温度前，试件内部个别接触点接触失效，对结构整体受力状况影响较小；（2）稳定扩展阶段，温度达到断裂温度前，随着温度的降低，接触力增加，裂缝沿试件薄弱部位发展，微裂缝数量缓慢稳定增长；（3）不稳定扩展阶段，温度达到断裂温度后，短时间内温度应力下降了66%,裂缝总量增加了132条，微裂缝已汇聚成可见的宏观裂缝，并沿着构造相对薄弱的位置快速扩展，导致试件失去整体承载力。

To clarify the intrinsic relationship between the mechanical properties of asphalt and its fraction composition, the SARA fraction composition and six macroscopic mechanical properties (critical cracking temperature (TCR), fatigue life (Nf), non-recoverable creep (Jnr3.2), penetration, ductility, and softening point) were investigated for 16 asphalt samples. Fraction contents of asphaltene and aromatic are strongly correlated with TCR and ductility (R2 > 0.92) that characterize the ability of asphalt to adapt to deformation at low and medium temperatures. Heavy fraction (asphaltene and resins) content is also strongly correlated with (R2 > 0.90) penetration and Jnr3.2 that characterize the resistance of the asphalt to overall deformation at medium and high temperatures. To express the changes in the four fractions simultaneously with one indicator, a statistic, average deviation of the fractions between the given asphalt and its original (marked sigma), is introduced in this study to characterize the degree of asphalt aging based on the fraction changes. It normalizes the four simultaneous change indicators (percentage of SARA fractions) during asphalt aging into one indicator. This new indicator has a strong correlation with several mechanical performance indicators of asphalt, where it is strongly correlated with TCR (R2 > 0.90), ductility, and penetration, which are also well correlated with Jnr3.2 (R2 > 0.85), Nf (R2 > 0.75), and softening point (R2 > 0.75).

To investigate the flow characteristics of pore water in asphalt pavement and the variation law of the pore water pressure under vehicle loading, a novel method based on BA network and quartet structure generation set method was proposed to reconstruct the three-dimensional (3D) pavement model with pores. The permeability coefficient and the gradation curve were adopted to evaluate the reliability and stability of the random growth pavement model. Then, the tire-fluid-pavement coupling model was established with FLUENT 3D based on the fluid Mie-Gruneisen state equation. According to the built fluid-solid coupling model, the pressure-velocity coupled finite volume algorithm was applied to study the distribution of the pore water pressure in asphalt pavement. Results show that the pore water pressure in asphalt pavement decays periodically with time under vehicle loading. For different types of asphalt pavement, the pore water pressure in open-graded friction course (OGFC) pavement is the smallest during the whole process. Moreover, the peak values of the pore water pressure decrease in the order of asphalt concrete (AC) pavement, stone mastic asphalt (SMA) pavement, and OGFC pavement. The maximum negative value of the pore water pressure is generally less than 0.3 times the maximum positive values. As for saturated pavement pores, the pore water pressure is hardly affected by the water film thickness. The positive peak value of the pore water pressure increases on an approximate parabolic curve as the vehicle speed improves gradually, while the negative one remains largely unchanged. The results are expected to help reduce tire hydroplaning risk and provide guidance for the selection of asphalt mixtures of drainage asphalt pavement.