Analysis of Automatic Steering Control for Highway Vehicles with Look-down Lateral Reference Systems

SUMMARY

In this paper, steering control for passenger cars on automated highways is analyzed, concentrating on look-down reference systems. Extension of earlier experimental results for low speed to highway speed is shown to be non-trivial. The limitations of pure output-feedback of lateral vehicle displacement from the road reference are examined under practical constraints and performance requirements like robustness, maximum lateral error and comfort. The in-depth system analysis directly leads to a new alternative design direction which allows to preserve look-ahead reference systems for highway speed automatic driving.     

Lateral Stability of Towed Flexible Vehicles

The highway transport of mobile homes is a matter of concern for the increasingly safety-minded driving public. The low speeds of towed vehicles necessary to maintain stability, together with the requirements for excessive lane widths due to clearance for the lateral motion, result in increased likelihood of traffic accidents, impeded traffic flow, and reduced highway capacity. A safe increase in the stable cruising speed, coupled with a decreased amplitude in the pendular motion helps alleviate all three of the aforementioned problems. Energy input at hitch point and lateral forces between the road and tires permit lateral vehicular motions, which occur above a critical speed, to increase in amplitude until possibly a limit cycle or instability is reached. One would expect that structural dynamics could have a pronounced influence on the lateral response of towed vehicles with large and relatively flexible chassis, such as mobile homes. The objective of this research is to determine the influence of chassis structural parameters on the lateral stability of towed flexible bodies during transport. The mass of the towing vehicle is assumed infinitely large, thus eliminating any dynamic interconnection between the towing and towed vehicles. The assumed modes method is used to describe the lateral deflection of the flexible towed vehicle. Results of the study of this model indicate that increase in structural rigidity of towed vehicle increases the critical towing speed whereas increase in the tire cornering coefficient reduces the safe towing speed, which is true only for this simplified model where the dynamic interaction with the towing vehicle is not included.     

Effects of Model Complexity on the Performance of Automated Vehicle Steering Controllers: Model Development,Validation and Comparison

SUMMARY

Recent research on autonomous highway vehicles has begun to focus on lateral control strategies. The initial work has focused on vehicle control during low-g maneuvers at constant vehicle speed, typical of lane merging and normal highway driving. In this paper, and its companion paper, to follow, the lateral control of vehicles during high-g emergency maneuvers is addressed. Models of the vehicle dynamics are developed, showing the accuracy of the different models under low and high-g conditions. Specifically, body roll, tire and drive-train dynamics, tire force saturation, and tire side force lag are shown to be important effects to include in models for emergency maneuvers. Current controllers, designed for low-g maneuvers only, neglect these effects. The follow on paper demonstrates the performance of lateral controllers during high-g lateral emergency maneuvers using these vehicle models.     

Effects of Model Complexity on the Performance of Automated Vehicle Steering Controllers: Model Development, Validation and Comparison

Recent research on autonomous highway vehicles has begun to focus on lateral control strategies. The initial work has focused on vehicle control during low-g maneuvers at constant vehicle speed, typical of lane merging and normal highway driving. In this paper, and its companion paper, to follow, the lateral control of vehicles during high-g emergency maneuvers is addressed. Models of the vehicle dynamics are developed, showing the accuracy of the different models under low and high-g conditions. Specifically, body roll, tire and drive-train dynamics, tire force saturation, and tire side force lag are shown to be important effects to include in models for emergency maneuvers. Current controllers, designed for low-g maneuvers only, neglect these effects. The follow on paper demonstrates the performance of lateral controllers during high-g lateral emergency maneuvers using these vehicle models.     

Automated Vehicle Merging Maneuver Implementation for AHS

Summary This paper presents a real-time implementation of a general merging algorithm for automated highway systems. A merging control problem is proposed first. A real-time algorithm is then presented, which is used to calculate a smooth reference speed trajectory for the merging vehicle based on the speed of the main lane vehicle. This algorithm can also be applied even when the main lane vehicles change speed. To make the algorithm adapt to different road layouts and to increase safety, a concept of virtual platooning is proposed. It effectively shifts the time of platoon formation forward prior to the start of real merging. Aspects closely related to real-time implementation are discussed, such as the controller adopted, the use of magnetometer based distance measurement and information passing by communication from main lane vehicles. Test results are presented and briefly analyzed.     

公路平曲线设计用曲线元素的研究

在分析国内外横向力系数相关研究的基础上，确定适合我国的横向力系数μ标准，建立适合我国道路和交通特性的平曲线设计用元素。     

Traffic calming measures: An evaluation of four low-cost TCMs' effect on driving speed and lateral distance

The transition from rural highways that afford higher speeds, to urban communities with lower speed limits and wide ranges of road users is a critical safety issue in Northern Iran that such transitions are frequent along a high-way running approximately parallel to the Caspian Sea shoreline and linking >50 urban communities. This study aims to investigate the efficiency of 4 low-cost traffic calming measurements (TCM) at a simulated 1.5 km length of this rural highway as a representative. 39 participants with at least 3 years of driving experience took part in this study, and comparisons of driver behaviors in case of speed and lateral position as a safety index in 4 scenarios and base scenario were outputted. MANOVA analysis was conducted on speed and lateral position data outputted from the simulator device, at the entry into the urban community. Comparison of mean speed results obtained revealed that all 4 treatments significantly reduced the mean speed of drivers. In this respect, the benefits of modified road signs were proven to be as successful as road surface markings. As another criterion for safety, the investigation showed road signs and transverse rumble strips increased lateral position, but the pattern of peripheral hatched markings significantly reduced the lateral position. In case of speed reduction, maintaining the reduced speed is another issue that has been resulted that as soon as TCMs end up, the speed increases, however, does not reach the former values.     

基于因子分析与熵值法的不同隧道侧向宽度下驾驶负荷模型

为探究隧道侧向宽度对驾驶心理及行为的影响机理，采用眼动仪、CAN-OBD测速仪等设备在滨莱高速试验场开展不同侧向宽度场景实车试验，获取30名男性驾驶人在不同侧向宽度场景下生心理及驾驶行为数据；以心率均值、车速差、速度标准差、平均注视持续时间和注视时间标准差为关键变量，建立基于因子分析与熵值法的驾驶负荷量化模型，量化评价不同侧向宽度下驾驶负荷变化规律；基于K-means聚类算法确定不同等级驾驶负荷阈值，结合ROC曲线的分类判别和最大约登指数值，提出隧道侧向宽度临界阈值计算方法。研究结果表明：当设计速度为120 km·h^-1时，采用较大的隧道侧向宽度不仅有利于提高运行车速，同时可减小驾驶负荷；相较于左、右侧侧向宽度分别为0.75 m和1.25 m的标准断面设计尺寸，隧道左、右侧侧向宽度增加至1.00 m和1.50 m时，小型车和大型车驾驶人运行车速分别提升4.5%和3.6%,驾驶负荷分别减小31%和29%;不同侧向宽度下驾驶负荷低、中、高3个等级对应的阈值为0.23和0.42,隧道左侧最佳侧向宽度阈值为0.75～1.00 m,右侧最佳侧向宽度阈值为1.25～1.50 ...     

城市道路与干线公路平交口差异化协调设计

普通干线公路和城市道路由于技术标准体系和管理模式的不同,决定了各自在功能定位、构造和设计方法上均有较大差异.针对现状干线公路与城市道路平面交叉口存在的问题和原因,分析干线公路和城市道路平交口衔接要素的差异性,并从城市道路与干线公路平面交叉口差异化协调设计方面提出合理可行的设计方法,以期能够为类似工程实践提供设计参考.     

Nonlinear PI front and rear steering control in four wheel steering vehicles

Vehicle steering dynamics show resonances, which depend on the longitudinal speed, unstable equilibrium points and limited stability regions depending on the constant steering wheel angle, longitudinal speed and car parameters.

The main contribution of this paper is to show that a combined decentralized proportional active front steering control and proportional-integral active rear steering control from the yaw rate tracking error can assign the eigenvalues of the linearised single track steering dynamics, without lateral speed measurements, using a standard single track car model with nonlinear tire characteristics and a non-linear first-order reference model for the yaw rate dynamics driven by the driver steering wheel input. By choosing a suitable nonlinear reference model it is shown that the responses to driver step inputs tend to zero (or reduced) lateral speed for any value of longitudinal speed: in this case the resulting controlled vehicle static gain from driver input to yaw rate differs from the uncontrolled one at higher speed. The closed loop system shows the advantages of both active front and rear steering control: higher controllability, enlarged bandwidth for the yaw rate dynamics, suppressed resonances, new stable cornering manoeuvres, enlarged stability regions, reduced lateral speed and improved manoeuvrability; in addition comfort is improved since the phase lag between lateral acceleration and yaw rate is reduced.

For the designed control law a robustness analysis is presented with respect to system failures, driver step inputs and critical car parameters such as mass, moment of inertia and front and rear cornering stiffness coefficients. Several simulations are carried out on a higher order experimentally validated nonlinear dynamical model to confirm the analysis and to explore the robustness with respect to unmodelled dynamics.     

车-车协同下无人驾驶车辆的换道汇入控制方法

多车协同驾驶是智能车路系统领域的研究热点之一,可有效降低道路交通控制管理的复杂程度,减少环境污染的同时保障道路交通安全。基于多车协同驾驶控制结构,提出了一种无人驾驶车辆换道汇入的驾驶模型及策略,系统分析了多车协同运行状态的稳定条件。在综合分析无人驾驶车辆换道汇入的协作准则、安全性评估后,基于高阶多项式方法,结合车辆运行特性,通过引入乘坐舒适性的指标函数,设计得到无人驾驶车辆换道汇入的有效运动轨迹。通过研究汇入车辆与车队中汇入点前、后各车辆的运动关系,详细分析车辆发生碰撞的类型和影响因素,给出避免碰撞的条件准则,从而确保无人驾驶车辆汇入过程中多车行驶的安全性和稳定性。基于车辆运动学建立车辆位置误差模型,结合系统大范围渐进稳定的条件,选取线速度和角速度作为输入,应用李雅普诺夫稳定性理论和Backstepping非线性控制算法,设计了无人驾驶车辆换道汇入后的路径跟踪控制器。仿真试验和实车试验结果表明：所设计的换道汇入路径是可行、安全的,控制器具有良好的跟踪效果,纵向和横向的距离误差在15 cm以内,方向偏差的相对误差在10%以内。研究结果为智能车路系统中的多车状态变迁与协同驾驶研究提供了参考,可服务于未来道路交通安全设计和评价。     

Nonlinear PI front and rear steering control in four wheel steering vehicles

Vehicle steering dynamics show resonances, which depend on the longitudinal speed, unstable equilibrium points and limited stability regions depending on the constant steering wheel angle, longitudinal speed and car parameters.

The main contribution of this paper is to show that a combined decentralized proportional active front steering control and proportional-integral active rear steering control from the yaw rate tracking error can assign the eigenvalues of the linearised single track steering dynamics, without lateral speed measurements, using a standard single track car model with nonlinear tire characteristics and a non-linear first-order reference model for the yaw rate dynamics driven by the driver steering wheel input. By choosing a suitable nonlinear reference model it is shown that the responses to driver step inputs tend to zero (or reduced) lateral speed for any value of longitudinal speed: in this case the resulting controlled vehicle static gain from driver input to yaw rate differs from the uncontrolled one at higher speed. The closed loop system shows the advantages of both active front and rear steering control: higher controllability, enlarged bandwidth for the yaw rate dynamics, suppressed resonances, new stable cornering manoeuvres, enlarged stability regions, reduced lateral speed and improved manoeuvrability; in addition comfort is improved since the phase lag between lateral acceleration and yaw rate is reduced.

For the designed control law a robustness analysis is presented with respect to system failures, driver step inputs and critical car parameters such as mass, moment of inertia and front and rear cornering stiffness coefficients. Several simulations are carried out on a higher order experimentally validated nonlinear dynamical model to confirm the analysis and to explore the robustness with respect to unmodelled dynamics.     

高速公路运营阶段安全性评价与分析

运用公路安全性评价标准对某现有高速公路运营阶段安全性进行评价与分析,通过计算运行速度和现场实测运行速度对其进行安全性检验,同时引入交通事故调查分析安全评价法鉴别事故黑点,有针对性地进行道路安全改造措施,保证车辆的行车安全。     

速度管理技术研究

为了提高公路的通行效率和安全性,制定了公路速度管理技术方案流程,采用实地观测试验和速度统计分析方法研究并提出了限速区划分和取值方法;根据几何设计参数、隧道分布、安全水平将路段规律划分为大限速区和局部限速区;提出结合运行速度、行程车速、路侧环境、历史事故等技术参数设定基本限速值的方法和修正基本限速值的方法,并采用实证分析验证方法的可行性。结果表明:提出的速度管理方案制定流程、限速区的划分、限速值的取值方法、限速方法的选择等具有很好的实用价值,能有效地解决速度管理的关键技术问题。     

一座公路下承式钢桁梁桥的结构设计

下承式钢桁梁桥因其具有建筑高度低、施工速度快和耐久性好等优点,可以成为中等跨度公路桥梁中有竞争力的桥型。在一座公路下承式钢桁梁桥的结构设计中,采用了板式桥门架和钢-混凝土组合结构桥面系,介绍该桥的设计特点与拖拉架设施工方案,可供桥梁设计参考。     

IntelliWay-变耦合模块化智慧高速公路系统一体化架构及测评体系

根据当前智慧高速公路系统的发展历程,总结一些典型的车路协同系统逻辑与物理模型。在总结国内外智慧高速公路系统的整体架构之后,提出新一代智慧高速系统的总体架构-IntelliWay,包括智慧高速公路系统分层模块化架构、基于变耦合程度的智能分级和基于事件驱动的数据分发机制。同时,根据当前智慧高速公路系统的主流应用技术,总结车载高精度定位、高级驾驶辅助系统(Advanced Driver Assistance System, ADAS)与车载总线、路侧设备优化、异构网络融合、网络负载均衡、网络信息安全、多传感器融合与协同感知、以用户为中心的场景自适应信息发布、车辆群体协同自动驾驶、基于大数据与人工智能的交通态势预测、车道级主动交通管理、组件式应用服务开发等驱动智慧高速公路系统快速发展的新兴技术研究现状,然后基于以上关键技术的特点提出未来智慧高速公路系统应用的实施建议;分析广播式交通信息服务、主动交通管理、伴随式信息服务、自动驾驶专用道、车辆队列协同驾驶等智慧高速公路系统的典型应用场景,进行智慧高速系统的测评方法分析和相关案例分析。最后,系统性地分析和预测智慧高速系统存在的挑战及未来发展趋势,以...     

高压钠灯与LED灯在公路隧道中的应用对比分析

对于隧道照明系统节能,除合理选择设计参数、智能调光控制等措施外,科学选用电光源也是实现照明节能的重要手段。结合公路隧道照明功能需求及光源特点,探讨常用节能光源高压钠灯与新型节能光源LED灯在隧道内应用的差异性,并对2种照明系统进行经济效益对比分析,为今后国内公路隧道工程合理选用光源提供参考。     

双车道公路车速标准差与交通冲突相关性研究

为了确定双车道公路车速标准差和交通冲突强度之间的相关性,分析了车速标准差、交通冲突强度与交通事故率之间的关系,理论上建立了车速标准差与交通冲突强度之间的内在联系。通过省道203现场实测数据分析表明双车道公路车速标准差与交通冲突次数之间存在显著的相关关系,多种回归模型分析结果认为多项式回归模型相关系数最高,达到了0.79,研究结果表明双车道公路车速标准差与交通冲突强度存在强相关性。     

公路超高设计应用探讨

超高设计是路线设计中的重要环节,也是曲线路段安全设计的关键内容之一。超高设计是否与平纵面线形相协调将直接影响到超高路段的路面排水以及车辆在曲线路段行驶的横向稳定性和舒适安全性。在JTG B01-2003《公路工程技术标准》和JTG D20-2006《公路路线设计规范》的基础上,对超高的一些主要控制因素进行分析并初步探讨...     

中国公路运行速度体系与工程应用技术研究

为创建中国公路运行速度理论、方法与技术体系,提高公路安全设计水平,在连续10年分阶段对中国20个省区35条高速和一级公路、39条二级及以下双车道公路现场数据采集、试验观测与事故调查的基础上,系统研究了中国公路交通特性、运行速度特征与交通安全的关系,针对高速公路、一级公路、双车道公路等研究对象,采用理论分析、数值计算、室内模拟试验、实体工程观测与实车现场测试相结合的方法,揭示了中国公路运行速度的特征与规律,提出了符合中国公路交通特点的运行速度代表车型划分标准,系统建立了各级公路及关键路段运行速度模型,创新集成了公路路线安全综合评价、公路路线安全设计、公路速度综合控制等工程应用技术及相关标准、指标体系。结果表明:该系列成果填补了中国公路运行速度应用模型、设计与速度控制基础理论研究方面的空白,为公路安全设计、评价及科学地进行速度控制提供了成套技术支撑。