用于微观仿真车辆模型中轨迹的简化算法

实际车辆运行轨迹的测量和计算都比较复杂.现存的微观仿真车辆模型,往往都回避了车辆轨迹的计算,而用直线运行来近似代替.构建微观车辆模型时,在影响车辆运行轨迹的各个因素中,可以只考虑前轮转向角和前后轴间距离2个主要因素,而质量、摩擦、刚体系数等其他次要因素是可以忽略的.据此,给出了车辆运行轨迹计算的简化算法,并为此进行了若干试验论证.结果表明,这种简化,一方面使得车辆微观模型在轨迹上更加接近于真实,另一方面,算法计算量小,是微观仿真中可以接受的.     

公交车辆运行微观交通仿真模型研究

介绍了上海交通大学与吉林大学共同开发的微观交通仿真系统MTSS的体系结构;建立了公交网络描述模型、公交车辆产生模型、乘客需求模型、公交站点事件反应模型和公交车辆运行模型;以微观交通仿真系统MTSS为仿真平台构建了公交车辆运行微观仿真模型;对上海市斜土路非港湾式站点与华山路港湾式站点进行了实地数据调查,利用实测数据对建立的公交车辆运行微观交通仿真模型进行了验证,测量值与仿真值之间的误差在10%以内。验证结果表明,建立的公交车辆运行微观交通仿真模型可以较好的描述公交车辆的运行过程以及与其他交通流之间的相互影响关系。     

无人驾驶车辆轨迹跟踪控制研究

为了提升智能车辆在轨迹跟踪控制中的性能,文章基于车辆运动学模型建立了一种带有前馈补偿和反馈最优控制策略的线性二次型调节器(LQR)轨迹跟踪控制算法。并通过搭建Carsim/Simulink联合仿真模型,验证该算法在不同工况下的轨迹跟踪效果。结果表明,该算法在不同车速和不同路面附着条件下都能保证无人驾驶车辆准确地跟踪参考轨迹,且具有较强的鲁棒性。     

基于车辆动力学模型的换道轨迹规划研究

针对自动驾驶车辆换道轨迹规划时的操纵稳定性问题，基于CarSim/Simulink仿真平台建立了车辆动力学模型，构建了轨迹规划系统框架，通过轨迹信息后处理并提出了目标函数设计，进行了横向控制序列采样以保证车辆的稳定与极限性能，完成了算法对轨迹的综合评价选优。随后开展了仿真试验，对比分析了轨迹跟踪控制系统下的实际轨迹、最优规划方法所规划的换道轨迹。仿真结果表明，该轨迹规划系统框架及算法模型能有效提高车辆的操纵稳定性，可实现冰雪路面等极端工况下自动驾驶车辆换道轨迹规划。     

基于车辆位置与速度特征的驾驶行为模式分类方法

精细车辆轨迹中包含连续的时间戳、位置，以及速度等信息。通过对车辆轨迹数据进行量化表达与挖掘分析，可以实现对车辆行为模式的分类。现有研究大多关注对位置的聚类，很少对车速、加速度等特征进行研究分析，而车速等是反映驾驶行为模式的重要特征。为了将轨迹多维信息纳入分析框架，研究了基于位置与速度特征的车辆轨迹行为模式分类方法。为克服现有行为模式分类方法的维度单一性，运用豪斯多夫轨迹距离算法计算出位置和速度特征的综合距离矩阵，针对豪斯多夫距离算法鲁棒性差的缺点，采用单向豪斯多夫距离90%分位值对算法进行了改进，降低噪声影响。同时，引入了车辆位置和速度来进一步提高分类的准确性，运用多次分层聚类算法依次对位置与速度轨迹图进行分类，得到车辆位置和速度上的行为模式。以HighD数据集为样本，提取了三车道上的行车轨迹，验证了基于速度与位置特征的车辆行为模式分类方法。结果表明:①本方法可以得到位置和速度的综合行为模式，聚类平均准确率达到94.8%，优于DBTCAN准确率89.3%和t-Cluster准确率86.4%；②基于换道模式轨迹偏移率曲线的分析，得到了4种互异的典型车辆换道模式。该方法可利用多维轨迹数据对行车模式进行分类及行为辨识，在车辆轨迹分类与不良行为辨识方面具有应用潜力。      

航拍视频车辆检测目标关联与时空轨迹匹配

高解析度轨迹数据蕴含丰富车辆行驶与交通流时空信息.为从航拍视频中提取车辆轨迹,构建了车辆检测目标跨帧关联与轨迹匹配融合方法.采用卷积神经网络YOLOv5构建视频全域车辆目标检测,提出车辆动力学与轨迹置信度约束下跨帧目标关联算法,建立了基于最大相关性的断续轨迹匹配与融合构建算法,实现轨迹车辆唯一编号.将轨迹从图像坐标转换为车道基准下Frenet坐标,构建集合经验模态分解(EEMD)模型进行轨迹数据噪声消除.采用南京市快速路无人机拍摄的2组开源航拍视频,涵盖拥堵与自由流交通状态,对轨迹提取算法进行效果测试.结果表明,在自由流和拥挤条件下轨迹准确率分别为98.86％和98.83％,轨迹召回率为93.00％和86.69％,构建算法的轨迹提取速度为0.07 s/辆/m.该方法处理得到的详细车辆时空轨迹信息能为交通流、交通安全、交通管控研究提供广泛的数据支撑,数据公开于http://seutraffic.com/.     

城市道路车辆排放测试与模拟

以长春市部分主干道为试验研究路段,采用一种车载排放测量仪器在实际道路上进行了单车排放试验,运用多项式回归的方法,整合车辆运行状况和排放数据,建立了单车实际道路微观排放模型。利用合作开发的基于路径的微观交通仿真系统与单车微观排放模型的有机结合,开发了一种可预测不同交通状况下交通干道排放的有效系统,并进行了仿真计算。结果表明:该系统不但可估算并预测车辆在某一路段的污染物排放水平,还可评价交通管理改进措施对车辆排放的影响。     

车道变换期望运行轨迹仿真

车道变换行为在实施过程中会产生交通冲突,降低道路系统的运行效率,严重时会引发交通事故.文中根据曲率的变化将车道变换过程划分为4个阶段,同时引入β样条曲线,在给定边界条件的基础上,确定β样条曲线的反求算法.在车辆转角、转角变化率及车辆的驾驶行为等约束条件下,确立车道变换运行速度与车道变换长度的关系,进而计算轨迹参数.以 Matlab 仿真计算轨迹曲线,并与实测数据对比,分析结果验证了模型的有效性.     

交叉口无干扰条件下右转机动车轨迹建模

利用视频提取技术,对不同几何条件交叉口的右转车辆数据进行采集,并利用Track pro软件获得车辆位置坐标,计算车辆平均运行轨迹;然后分别用对数函数和二次多项式对轨迹进行拟合,通过比较拟合结果,确定右转机动车轨迹模型为对数函数模型;同时通过分析交叉口转角、出口道位置、车辆速度等轨迹影响因素与轨迹参数之间的关系,对模型参数进行了标定;最后选择工程实例,利用实测数据对模型进行了验证。结果表明,利用模型计算的轨迹坐标点与实际值的最小相对误差为0.34%,验证了模型的有效性。     

铰接车辆在不平道路行驶的动力学仿真

本文将铰接车辆简化为一多体系统，把轮胎简化为三维分段性弹簧，通过引入刚性位移机制，考虑路面不平度及其产生的坡度对车辆动力性的影响。建立了铰接车辆在不平路面行驶的动力学模型，列出了运动微分方程，提出了铰接车辆在不平路面行驶的动力学仿真算法，并通过实验验证了此模型及仿真算法的正确性。     

前轮转角和车轮制动状态对汽车轨迹模拟的影响

对于碰撞后失去动力的汽车，建立其运动轨迹的计算机模型需要碰撞后汽车的初始速度和前轮转角，制动情况等初始值作为轨迹模型的输入参数，以便观察碰撞发生后的汽车运动情况。分析了碰撞后汽车车轮的受力情况，给出不同初始值情况下的轨迹模拟模型。分析结果得出，车轮在自由状态下，前轮的转角对汽车的运动距离有较大影响；当前轮转角为零时，汽车的质心运动几乎为一条直线；当车轮未完全抱死且前轮转角不为零时，汽车的质心运动为一条曲线。     

Dynamic vehicle–track interaction in switches and crossings and the influence of rail pad stiffness – field measurements and validation of a simulation model

A model for simulation of dynamic interaction between a railway vehicle and a turnout (switch and crossing, S&C) is validated versus field measurements. In particular, the implementation and accuracy of viscously damped track models with different complexities are assessed. The validation data come from full-scale field measurements of dynamic track stiffness and wheel–rail contact forces in a demonstrator turnout that was installed as part of the INNOTRACK project with funding from the European Union Sixth Framework Programme. Vertical track stiffness at nominal wheel loads, in the frequency range up to 20?Hz, was measured using a rolling stiffness measurement vehicle (RSMV). Vertical and lateral wheel–rail contact forces were measured by an instrumented wheel set mounted in a freight car featuring Y25 bogies. The measurements were performed for traffic in both the through and diverging routes, and in the facing and trailing moves. The full set of test runs was repeated with different types of rail pad to investigate the influence of rail pad stiffness on track stiffness and contact forces. It is concluded that impact loads on the crossing can be reduced by using more resilient rail pads. To allow for vehicle dynamics simulations at low computational cost, the track models are discretised space-variant mass–spring–damper models that are moving with each wheel set of the vehicle model. Acceptable agreement between simulated and measured vertical contact forces at the crossing can be obtained when the standard GENSYS track model is extended with one ballast/subgrade mass under each rail. This model can be tuned to capture the large phase delay in dynamic track stiffness at low frequencies, as measured by the RSMV, while remaining sufficiently resilient at higher frequencies.     

High fidelity quasi steady-state aerodynamic model effects on race vehicle performance predictions using multi-body simulation

We described in this paper the development of a high fidelity vehicle aerodynamic model to fit wind tunnel test data over a wide range of vehicle orientations. We also present a comparison between the effects of this proposed model and a conventional quasi steady-state aerodynamic model on race vehicle simulation results. This is done by implementing both of these models independently in multi-body quasi steady-state simulations to determine the effects of the high fidelity aerodynamic model on race vehicle performance metrics. The quasi steady state vehicle simulation is developed with a multi-body NASCAR Truck vehicle model, and simulations are conducted for three different types of NASCAR race tracks, a short track, a one and a half mile intermediate track, and a higher speed, two mile intermediate race track. For each track simulation, the effects of the aerodynamic model on handling, maximum corner speed, and drive force metrics are analysed. The accuracy of the high-fidelity model is shown to reduce the aerodynamic model error relative to the conventional aerodynamic model, and the increased accuracy of the high fidelity aerodynamic model is found to have realisable effects on the performance metric predictions on the intermediate tracks resulting from the quasi steady-state simulation.     

Black-box modelling of nonlinear railway vehicle dynamics for track geometry assessment using neural networks

ABSTRACT

The use of vehicle dynamics simulation for the track geometry assessment gives rise to new demands. In order to analyse the responses of the vehicles to the measured track geometry defects, the integration of the simulation process in the measurement chain of the track geometry recording car is envisaged. Fast and reliable simulation results are required. This work studies the use of black-box modelling approaches as an alternative to multi-body simulation. The performances of different linear and nonlinear black-box models for the simulation of the vertical and lateral bogie accelerations are compared. While linear transfer function models give good results for the simulation of the vertical responses, their use is not suitable for the highly nonlinear lateral vehicle dynamics. The lateral accelerations are best represented by recurrent neural networks. For the training and validation on high-speed lines using measured vehicle responses, the performance of the black-box simulation outperforms the multi-body simulation. Due to the larger variability of track design and track quality conditions on conventional lines, the model performance degrades and depends significantly on the analysed vehicle type and the track characteristics.     

Influence of wheel–rail contact modelling on vehicle dynamic simulation

This paper presents a comparison of four models of rolling contact used for online contact force evaluation in rail vehicle dynamics. Until now only a few wheel–rail contact models have been used for online simulation in multibody software (MBS). Many more models exist and their behaviour has been studied offline, but a comparative study of the mutual influence between the calculation of the creep forces and the simulated vehicle dynamics seems to be missing. Such a comparison would help researchers with the assessment of accuracy and calculation time. The contact methods investigated in this paper are FASTSIM, Linder, Kik–Piotrowski and Stripes. They are compared through a coupling between an MBS for the vehicle simulation and Matlab for the contact models. This way the influence of the creep force calculation on the vehicle simulation is investigated. More specifically this study focuses on the influence of the contact model on the simulation of the hunting motion and on the curving behaviour.     

Sliding window method for vehicles moving on a long track

The rail is modelled as a simply supported beam in the vehicle–track coupled dynamics. The beam is formulated by a partial differential equation that is transformed into an ordinary differential equation by the method of mode superposition for numerical calculation. However, the size of the matrix that is formed by the mode-superposition method increases significantly with track length, which limits the calculation efficiency. Some methods have been developed to solve this calculation issue, but they diminish the merits of the vehicle–track coupled dynamics, which would systematically investigate the dynamics of a vehicle and a track from the entire vehicle–track system. A new method is developed to resolve this contradiction. First, a theory based on a sliding window is established to improve the computational stability with respect to the length and the window-movement ratio. Then, two methods, namely finite element method analysis and an analytical solution, are used to verify the accuracy of the new method, which is highly efficient when used in a vertical half-vehicle–track coupled model to calculate the vehicle response when the vehicle moves on a long track. The results of the vehicle response calculated with and without the sliding window show good consistency.     

An approach for the validation of railway vehicle models based on on-track measurements

This paper proposes an approach for the validation of railway vehicle models based on on-track measurements. The validation of simulation models has gained importance with the introduction of new applications of multi-body simulation in railway vehicle dynamics as the assessment of track geometry defects, the investigation of derailments and the analysis of gauging. These applications are not only interested in qualitative predictions of the vehicle behaviour but also in precise quantitative results of the safety and comfort relevant vehicle responses. The validation process aims at guaranteeing that the simulation model represents the dynamic behaviour of the real vehicle with a sufficient good precision. A misfit function is defined which quantifies the distance between the simulated and the measured vehicle response allowing to evaluate different models at different running conditions. The obtained modelling errors are compared to the measurement uncertainty estimated for one vehicle using repeatability analysis.     

无砟轨道路基动力响应影响因素分析

以双块式无砟轨道路基典型结构为研究对象,分析车辆轴重、结构层间接触条件、轨道结构整体模量、支承层模量和基床表层模量等对路基面动力响应的影响,分析路基动力响应对各参数的敏感性。数值仿真结果表明:在车辆单轴荷载作用下,路基面动应力分布表现为横向均匀、纵向三角形的基本形式;对路基面动应力沿线路纵向分布长度影响的主要因素,是无砟轨道结构的整体刚度、车辆轴重、支承层模量等;结构面间接触状态劣化导致无砟轨道结构刚度的降低和路基面的动压力增大。     

中国公路车-桥耦合振动车辆模型研究（双语出版）

为了提出适用于中国车-桥耦合振动分析的车辆动力分析模型,首先基于中国桥梁规范中的设计车辆荷载,结合大量调查统计数据和等效静力分析方法,初步拟定车辆动力分析模型的几何尺寸、质量、刚度、阻尼等参数取值,并与国内外广泛采用的几种车辆模型的参数取值进行对比。接着选取4座钢筋混凝土简支梁桥并建立其三维有限元模型,基于车-桥耦合振动数值模拟分析车辆模型的刚度、阻尼等参数对桥梁上动力冲击系数的影响,并对比几个不同车辆模型对动力冲击系数的影响。最后,选择中国湖南省境内一座实桥和几辆不同轴数的重车开展实桥试验,将实测动力冲击系数与所提车辆模型数值模拟获得的冲击系数进行对比。结果表明：动力冲击系数随车辆总质量的增大而减小,随车辆整体刚度的增大而增大,但随车辆整体阻尼的增大呈先减小后增大的趋势;单个车轴的刚度和阻尼对动力冲击系数的影响不明显;车辆总质量是导致不同车辆模型作用下动力冲击系数差异的主要因素;数值模拟结果与实测结果吻合良好,验证了所提车辆模型及参数取值的合理性;该车辆模型可用于中国的设计车辆荷载作用下桥梁的动力响应分析和相关研究,也可用于估算重量相当的不同类型车辆对桥梁的动力冲击效应。     

Vehicle-Track Dynamics in the Mid-Frequency Range

During the last years railway companies have observed increasing problems with track damage like rail corrugation, deterioration of ballast or unround wheels. Since the origin of these damages is suspected in the mid-frequency dynamics, research activities in the frequency range from 50 up to 500 Hz have been initiated. The article demonstrates that in comparison to the low and high frequency range the knowledge about physical effects in the mid-frequency range is poor. Apart from a historical literature review on vehicle and track modelling, recently published methods and models are collated and problems in their mathematical treatise are mentioned. Regarding the vehicle, the paper shows the development starting with Klingel's massless wheelset model and ending with sophisticated elastic multibody system models. Concerning the track, different mathematical approaches in frequency and time domain are compared. In the mid-frequency range the pad, ballast and subsoil properties play an important role. Hence, the missing of experimentally validated models of these components is crucial. First attempts have been performed, which take into account the subsoil as layered half-space and the ballast as an assembly of viscoelastic rods. Besides the short time dynamics the article gives also an overview of the modelling of the wear phenomena mentioned above. An investigation of such long-term effects requires complex models of the entire vehicle-track system. The few wear models found in literature are discussed and first results are mentioned.