Implications of path tolerance and path characteristics on critical vehicle manoeuvres

Path planning and path following are core components in safe autonomous driving. Typically, a path planner provides a path with some tolerance on how tightly the path should be followed. Based on that, and other path characteristics, for example, sharpness of curves, a speed profile needs to be assigned so that the vehicle can stay within the given tolerance without going unnecessarily slow. Here, such trajectory planning is based on optimal control formulations where critical cases arise as on-the-limit solutions. The study focuses on heavy commercial vehicles, causing rollover to be of a major concern, due to the relatively high centre of gravity. Several results are obtained on required model complexity depending on path characteristics, for example, quantification of required path tolerance for a simple model to be sufficient, quantification of when yaw inertia needs to be considered in more detail, and how the curvature rate of change interplays with available friction. Overall, in situations where the vehicle is subject to a wide range of driving conditions, from good transport roads to more tricky avoidance manoeuvres, the requirements on the path following will vary. For this, the provided results form a basis for real-time path following.     

An alternative to FASTSIM for tangential solution of the wheel–rail contact

In most rail vehicle dynamics simulation packages, tangential solution of the wheel–rail contact is gained by means of Kalker's FASTSIM algorithm. While 5–25% error is expected for creep force estimation, the errors of shear stress distribution, needed for wheel–rail damage analysis, may rise above 30% due to the parabolic traction bound. Therefore, a novel algorithm named FaStrip is proposed as an alternative to FASTSIM. It is based on the strip theory which extends the two-dimensional rolling contact solution to three-dimensional contacts. To form FaStrip, the original strip theory is amended to obtain accurate estimations for any contact ellipse size and it is combined by a numerical algorithm to handle spin. The comparison between the two algorithms shows that using FaStrip improves the accuracy of the estimated shear stress distribution and the creep force estimation in all studied cases. In combined lateral creepage and spin cases, for instance, the error in force estimation reduces from 18% to less than 2%. The estimation of the slip velocities in the slip zone, needed for wear analysis, is also studied. Since FaStrip is as fast as FASTSIM, it can be an alternative for tangential solution of the wheel–rail contact in simulation packages.     

连续窄弯河段通航建筑物平面布置

依托湖南华容河旗杆咀船闸改建工程,采用数值模拟与通航船舶操纵模拟器相结合的研究方法,对船闸布置于连续窄弯河段凹岸,上、下游引航道均处于曲率半径较小的弯曲段的通航建筑物平面布置进行研究,并提出改善通航条件的方法及平面布置需要注意的事项,供类似工程参考。     

导轨式胶轮电车单元式铰接车体的铰接机构运动学分析

介绍了多模块铰接式胶轮承载的导轨式胶轮电车系统架构和主要技术参数。阐述了单元式铰接车体的组成和运动学关系。利用MSC ADAMS软件分析了车辆在小半径平曲线、小半径竖曲线及小半径S型曲线线路条件下的通过性能。校验了走行部与车体之间、车体自身之间是否有干涉发生,并计算了车体相对最大转角,确认铰接机构运行关系满足车辆运行需求。     

跨坐式单轨车辆的临界横向力与曲线限速

在离心力的作用下,跨坐式单轨车辆走行部一侧的稳定轮减载。根据稳定轮刚刚脱离轨面这一临界状态,定义此时车体离心力为临界横向力。采用达朗贝尔原理将跨坐式单轨车辆通过曲线的动力学问题转换为静力学问题,推导出临界横向力和稳定轮预压力之间的关系公式,并利用多体动力学软件UM验证了公式的准确性。依据临界横向力公式,从舒适度角度计算稳定轮预压力的合理取值,得到曲线最高限制速度和最低限制速度与稳定轮预压力、轨道梁超高率以及曲线半径之间的关系。结果表明:临界横向力与稳定轮和导向轮的预压力成线性关系;考虑运行安全性和舒适度要求,本文中车辆的稳定轮和导向轮预压力设置为7kN时,轨道梁最大超高率设置为6%比较合适。     

悬挂式单轨列车曲线通过性能分析

曲线通过性能分析是转向架设计的基础之一。使用多体系统动力学软件建立悬挂式单轨列车-轨道系统60自由度动力学模型,模型考虑轮胎-轨道接触非线性,空气弹簧和抗横摆减震器弹簧非线性。模拟悬挂式单轨列车通过曲线轨道时导向轮与轨道间法向接触力的动态变化过程,研究了空气弹簧水平刚度和轨距变化对转向架曲线通过性能的影响。结果表明:悬挂式单轨列车转向架具有不同于传统轨道车辆的曲线通过形态;空气弹簧水平刚度对转向架的曲线通过形态和导向轮法向接触力有显著的影响,水平刚度为0.01 MN/m时,相较于水平刚度0.1 MN/m,最大导向轮轨法向接触力可减小63.2%;轨距变化对转向架的曲线通过性能影响不明显,减小空气弹簧水平刚度可改善转向架的曲线通过性能。     

一个直接确定钢板梁腹板加劲肋间距的方法

介绍了一种在荷载作用下钢板梁腹板加劲肋间计算的简化方法。文中在构造要求许可范围内，对Ｃ函数进行曲线拟合，最后间距的确定归结为求解一个一元二次代数方程，较为方便。     

Research on Route Planning Method Based on Active-Attack Strategy

Aimed at modern high-density,high overlapped and powerful antipersonnel stealthy penetration environment,route planning techniques on active-attack strategy were thoroughly and further studied,in order to get good probability of survival and perfect efficiency of task accomplishment.It provides a new thought for and a new solution to the application of route planning in new era.     

互通立交安全性的设计探讨

互通立交的安全性除了遵循规范要求外,还应针对互通立交的具体特点,灵活运用其各要素.当然,在设计中也不应该为了追求互通区的安全性,而取高指标,增大规模,不考虑实用性等;在设计过程中应根据互通所在地形、设计方案以及桥梁结构物的设置等具体情况进行细致考虑、综合设计.     

公路平面线形自动化设计中拟合曲率图的识别和转化

公路平面线形设计中 ,如何将样条似合曲线转化成传统的平面线形 ,两者曲率图之间的转换是关键 .笔者重点阐述了拟合曲线曲率图转化成传统平面线形曲率图的自动识别方法 ,并用实例论证其可行性 ,然后利用得到的曲率图转化模式采用最小二乘法实现了曲率图和平面线形的转化 .