Comparison of In-Vehicle Auditory Public Traffic Information With Roadside Dynamic Message Signs

Dynamic message signs (DMS) have been widely used by transportation agencies to disseminate traffic information (referred to in this article as “public traffic information”) for decades. Unfortunately, their effectiveness is limited, based on the following reasons: they are costly, can only present a limited amount of information, and typically only display information in one language. The wide availability of smart devices and the development of connected vehicles offer the possibility to create “virtual” DMS (VDMS), utilizing geofencing and audible messages to convey public traffic information. This research compares the ability of VDMS to convey public traffic information with existing DMS. A mixed repeated-measure experiment using a driving simulator was designed that examined the impacts of driver age, information transmission mode, amount of information, and driving complexity on message comprehension. Forty-two participants were recruited and each of them was tested under different combinations of the three within-subject factors. Participant performance was measured in terms of message comprehension, distraction, and self-reported overall difficulty level in receiving messages. Results revealed that VDMS generally performs better than DMS as information content increases and driving condition complexity increases, regardless of driver age. VDMS increased message comprehension by 16% under relatively complex driving conditions, reduced driver reaction time to unexpected stimuli (as measured with a reduced time-to-brake of 0.39 s), and made the same messages easier to process and retain for drivers than DMS. Based on these results, it is recommended that transportation agencies give careful consideration to VDMS as a future strategy for delivering public traffic information in a connected vehicle environment.     

基于Q强化学习的AVB数据转发时延模型研究

为了提高音视频桥接技术(Audio/Video Bridge,AVB)数据时延分析结果的正确性,以AVB交换机处转发的数据为研究对象,在经典的AVB协议模型中融入Q强化学习理论,构造时延数学模型.在完成AVB协议模型和Q强化学习理论研究基础上,提出更加符合实际的AVB交换机数据转发策略,结合车载以太网数据转发时延影响因...     

Assessing the Potential Impacts of Connected Vehicles: Mobility,Environmental, and Safety Perspectives

The connected vehicle is a rapidly emerging paradigm aimed at deploying and developing a fully connected transportation system that enables data exchange among vehicles, infrastructure, and mobile devices to improve mobility, enhance safety, and reduce the adverse environmental impacts of the transportation systems. This study focuses on micromodeling and quantitatively assessing the potential impacts of the connected vehicle (CV) on mobility, safety, and the environment. To assess the benefits of CVs, a modeling framework is developed based on traffic microsimulation for a real network located in the city of Toronto, Canada, to mimic communication between enabled vehicles. In this study, we examine the effects of providing real-time routing guidance and advisory warning messages to CVs. In addition, to take into account the rerouting in nonconnected vehicles (non-CVs) in response to varying sources of information such as apps, global positioning systems (GPS), variable message signs (VMS), or simply seeing the traffic back up, the impact of fraction of non-CV vehicles was also considered and evaluated. Therefore, vehicles in this model are divided into; uninformed/unfamiliar not connected (non-CV), informed/familiar but not connected (non-CV) that get updates infrequently every 5 minutes or so (non-CV), and connected vehicles that receive information more frequently (CV). The results demonstrate the potential of connected vehicles to improve mobility, enhance safety, and reduce greenhouse gas emissions (GHGs) at the network-wide level. The results also show quantitatively how the market penetration of connected vehicles proportionally affects the performance of the traffic network. While the presented results are pertinent to the specifics of the road network modeled and cannot be generalized, the quantitative figures provide researchers and practitioners with ideas of what to expect from vehicle connectivity concerning mobility, safety, and environmental improvements.     

典型车联网基本安全消息机制分析

车联网基本安全消息的生成和传播是影响车联网安全应用及智能网联汽车有效性、可靠性的关键因素.在分析车联网基本安全消息基本定义的基础上,对国内外当前LTE-V2X、车载环境下的无线接入(Wireless Access in the Vehicular Environment,WAVE)等多种典型的车联网通信协议体系结构框架...     

智能网联趋势下车辆网关路由缓存研究与应用

伴随汽车智能网联发展,车辆电气网络架构行业趋势由1~2路CAN总线网络快速演变为7~8路CAN总线与4~5路百兆以太网相结合的融合网络架构。其中网关作为车辆网络的数据交互中心,提供了各网络之间的无缝通信,并需要以极低的延迟将这些数据进行可靠传输,这对低成本网关是一个巨大的挑战。提出了一种基于车载融合网络下低成本网关路由软件缓存区的设计方法,以路由软件缓存区去配合CAN控制器和以太网Switch硬件缓存区,设计中断式报文存储发送进程,将收到的数据实时发送到硬件发送缓存区,当硬件发送缓存区已满,则将报文存储到软件缓存区中。通过与软硬件缓存区的这种联动方式,能够实时的接收报文,保证报文不丢帧;也能够在目标总线负载率较大时,避免漏发报文以及保证发送报文周期。     

通信时延与丢包下智能网联汽车控制性能分析

网联协同控制是智能网联汽车的重要应用场景，而车联网的通信时延与丢包可能导致控制性能下降，甚至影响行车安全。为了分析时延与丢包对网联车辆控制的稳态与瞬态性能的影响，设计了网联控制器，并开展了仿真与实车试验。基于车辆动力学特性，将通信时延与丢包下的网联车辆控制分解为纵向控制与横向控制，进行了统一建模，并设计了控制器进行试验分析；搭建了网联自动驾驶的CarSim-Simulink联合仿真平台，及集成可模拟时延与丢包的LTE-V原理样机的智能网联汽车试验平台；开展了不同时延与丢包率下网联跟车控制与网联路径跟踪控制的仿真试验与实车试验。试验结果显示：时延与丢包对控制误差的影响形态有相似性；时延或丢包率取系统及工况参数有关的小值时，如试验中时延小于200 ms或丢包率小于20%，工况随机因素对控制误差的影响可能超过时延与丢包的影响；在更大的时延或丢包率下，时延与丢包的出现方式（如出现时机等）对控制误差影响更大。研究结果表明：能实现针对网联车辆控制系统通信特性的控制器优化设计，使得当时延与丢包在工况相关阈值内时，系统控制误差有界。所揭露的规律一方面可用于对造成危险控制误差的时延与丢包工况进行预警，另一方面也可用于基于给定的稳态或瞬态控制误差边界，判定对应工况允许的时延与丢包率边界。     

网联通信时延下的混合队列控制特性分析

针对CACC协同自适应巡航控制技术,探究其在车联网通信时延影响下,与驾驶员驾驶汽车共存而构成的混合队列系统的性能.从微观跟车行为角度,基于频域传递函数,推导通信时延下的CACC队列稳定最小跟车时距的理论表达式,并通过数值验证指出CACC队列稳定最小跟车时距随通信时延增大而增大的特性.从交通激波特性角度,针对无时延CAC...     

数据和知识双驱动下的土压平衡盾构结泥饼事件预警模型

针对施工中结泥饼事件成因机制复杂、预判难度大的问题，从数据建模和知识推理2种角度综合判断盾构结泥饼事件概率。从数据建模角度，采用无阈值递归图转换和极限学习机自编码器技术建立基于施工多维时序数据的结泥饼异常诊断子模型；从知识推理角度，提取土压平衡盾构结泥饼事件规则，形成事件诊断知识库，建立基于历史施工经验的结泥饼事件诊断子模型。基于2个子模型输出结果，采用综合概率法，建立数据和知识双驱动的结泥饼事件预警模型。实际工程应用表明： 数据和知识双驱动的预警模型能够有效预测结泥饼事件，且预警效果优于单一形式的子模型，较子模型的误报率更低，预警时间早于人工发现的结泥饼事件，为工程安全提供了技术保障。     

基于Synchro的单点交叉口信号配时优化研究

首先系统地介绍了信号配时模型的现有研究成果,然后分析了Srnchro仿真系统中信号配时优化模型、用于延误计算的百分比延误方法(PDM)模型、排队长度计算模型、停车次数计算模型、通行能力计算模型和服务水平等模型.以广州市天河北路与天河东路交叉口为例,使用延误、停车次数、排队长度组合成的综合性能指标对交叉口的当前信号相位、相序进行了全面的优化研究.应用Synchro系统优化后,最大车流量和通过能力比由1.24减小到1.02,平均控制延误由85.8 s减少到60.3 s,服务水平由F级提高到E级.试验结果表明应用Synchro系统可有效提高路口的控制效果.     

Schedule construction under precedence constraints in flexray in-vehicle networks

As embedded time-triggered applications have widely replaced mechanical systems in modern automobiles, holistic scheduling of tasks and messages of such applications on in-vehicle networks has become a critical issue. For offering QoS (Quality of Service) guarantees, the holistic schedule must satisfy numerous constraints such as protocol specifications, delay constraints and precedence constraints between tasks schedules and messages transmissions. Existing approaches to this problem search through a vast design space of all possible joint task and message schedules. This leads to a high complexity and limits the scalability of such approaches for scheduling the large scale systems. To cope with this problem, we propose an approach that divides the holistic scheduling problem to two sub-problems: the sub-problem of message scheduling and the sub-problem of task scheduling, while precedence relations and end-to-end information passing between task instances and messages are preserved and the end-to-end deadlines are guaranteed. This helps to reduce the workload on the problem solvers and improves efficiency and scalability. In the first sub-problem, our approach optimizes scheduling the set of messages and allocates time windows for scheduling each task with respect to precedence constraints, end-to-end deadlines and FlexRay protocol specifications. The length of each time window helps to preserve the respective tasks schedulability and to provide flexibility for both task and message scheduling. The objective is defined with respect to extensibility issues. In the second sub-problem, our approach optimizes schedule of the set of tasks with respect to their allocated time windows and timing constraints. The objective is defined with respect to latency issues. We optimize the solution to each sub-problem using Mixed Integer Linear Programming optimization framework. Performance evaluations show that, compared with existing holistic scheduling approaches, our approach is more scalable and obtains better solutions in a reasonable amount of time.     

Intelligent speed adaptation: Preliminary results of on-road study in Penang,Malaysia

The first field experiment with intelligent speed adaptation (ISA) in Malaysia was held in December 2010 in the State of Penang. Eleven private cars were instrumented with an advisory system. The system used in the present study included a vocal warning message and a visual text message that is activated when the driver attempts to exceed the speed limit. When the driver decreases the speed, the warning stops; otherwise it is continuously repeated. The test drivers drove the vehicles for three months with the installed system, and the speed was continuously logged in all vehicles. The warning was however only activated in the second month of the three month period. The present study aimed to evaluate the effects of an advisory ISA on driving speed, traffic safety, and drivers' attitude, behavior, and acceptance of the system. To examine these effects, both the survey and the logged speed data were analyzed and explored. The results show a significant reduction in the mean, maximum and 85th percentile speed due to the use of the system. However, there was no long-lasting effect on the speed when the system was deactivated. In the post-trial survey, drivers declared that the system helped them well in following the speed limits and that it assisted them in driving more comfortably. Furthermore, the warning method was more accepted compared to a supportive system, such as active accelerator pedal (AAP). After the trial, most drivers were willing to keep an ISA system.     

面向智能交通的无线传感网络分簇算法

无线传感网络是智能交通系统的关键组成部分.合理的分簇技术有利用于提高无线传感网络能量利用率.研究了基于孤点感知能效的无线传感网络分簇算法(INEEC),该算法将时间划分等间隔的轮,每一轮进行簇头选择,平衡簇头的能耗.在簇头选择阶段,每个节点先选择一个随机数,依据各节点的能量以及该区域的局部能量信息估计门限值.若随机数小于门限值,就成为簇头.每个簇头节点广播请求加入消息,其他节点接收消息后,加入最近的簇.若没有收到任何请求加入消息,节点就为孤点.仿真结果表明,相比于HEED和LEACH算法,该算法孤点数最少,传输时延最低,簇头分布更加均匀使总体能耗降低,网络寿命比HEED算法提高近23.5%,较好解决了同类算法在应用中能量效率较低、能耗较高、网络生命周期较短的关键问题.      

Experimental validation of a mathematical model of a reed-valve reciprocating air compressor from an automotive-braking system

Mathematical simulation is the process of designing a model of a real system and then conducting experiments with the simulation to understand the system’s behavior. Mathematical simulation is widely used for investigating and designing compressors, and with a minimal number of simplifying assumptions, mathematical models can be used in conjunction with modern computing tools to solve complicated problems. A considerable amount of previous research has focused on the mathematical modeling of reciprocating air compressors used in automotive braking. The aim of the present work was to experimentally validate the mathematical model for such compressors. We present a simplified and effective mathematical model for estimating compressor performance, and this model can easily be executed using personal computers. Parameters such as compressor speed, discharge pressure and clearance volume were evaluated in terms of their effect on the thermodynamic behavior of compressors. The model can predict cylinder pressure, cylinder volume, cylinder temperature, valve lift and resultant torque at different crank angles; it can also predict the free air delivered and the indicated power of the compressor. Therefore, the model has been validated using experimental results.     

面向人因的车路协同系统综合测试及影响评估

面向冬奥主干通道兴延高速，以驾驶人适应性为导向，构建一种面向人因的车路协同系统硬件在环效能测试平台，针对多种道路条件、交通状态、特殊事件等面向高速公路设计13种交通情境，从主、客观2个维度实现车路协同系统包括主观感受、高效性、安全性、生态性、舒适性、有效性6个方面的驾驶人适应性评价，分析车路协同驾驶状态下的综合评估指标及影响机理。主观评估结果显示，车路协同技术对驾驶人有积极作用，52%的被试认为车载预警信息可以使行车过程更安全。客观运行结果表明：由于车路协同状态下驾驶人对于前方道路危险状况的可预知性，导致驾驶人提前降速，运行速度降低，效率有所下降；车路协同条件下的加速度和换道次数明显减小，其安全性显著提升；由于车路协同系统避免了驾驶人对于突发危险状况的紧急制动，因此车辆的油耗、排放均明显降低，其生态性改善效果显著；归因于驾驶人对于车路协同系统熟悉程度不足，导致舒适度各系统存在不一致的结论，也表明驾驶人对于车路协同系统的接受度和信任度均有待进一步提高；驾驶人在车路协同条件下可获取不同路段的限速值和超速提示，其有效性表现出明显的优势，速度跟随比有显著提升。所构建的测试平台和指标体系为进一步深层次挖掘车路协同的作用机理奠定了基础。     

Empirical modeling of a polymer electrolyte fuel cell based on water transport investigation and current interrupt measurement

Water management is an important factor in the optimal performance of a polymer electrolyte fuel cell (PEFC). In this paper, a PEFC model that facilitates the control of PEFC membrane humidity is presented. An efficient modeling procedure using a combination of mathematical and experimental techniques is proposed. A simple mathematical structure for the model is adopted, and experiments to measure PEFC irreversibilities and net water transport across the membrane electrode assembly (MEA) are performed. The developed PEFC model effectively quantifies the irreversibilities in the PEFC output voltage and clarifies the relationship between PEFC performance and steady state water transport through the MEA. The proposed modeling procedure can effectively save time and cost during the controller / control algorithm design phase in PEFC system development.     

Enhanced selective forwarding scheme for alert message propagation in vehicular <Emphasis Type="Italic">ad hoc</Emphasis> networks

Vehicle-based applications were recently introduced to improve traffic safety and efficiency. These applications are classified into either safety-oriented or non-safety-oriented applications. Safety-oriented applications are typically provided by means of vehicle-to-vehicle (V2V) communications to support reliable and fast alert message propagation to all surrounding vehicles when an emergency occurs on the road. In vehicular ad-hoc network (VANET) broadcast-based packet forwarding is typically preferred for the propagation of urgent traffic-related information to all reachable nodes within a specified dangerous region. However, this approach may cause broadcast storm problems, which can lead to serious contention between transmissions from adjacent nodes. In this paper, we propose an alert message propagation scheme that is based on selective forwarding and aims to i) minimize the number of rebroadcasting nodes and ii) guarantee reliable and fast alert message delivery to all reachable nodes. Our scheme was evaluated using two different highway scenarios. The simulation results demonstrated that the performance of the proposed scheme was better than that of existing broadcast schemes in terms of the message delivery latency, the message delivery ratio, and the message rebroadcasting ratio.     

随车起重机伸缩臂的最佳伸缩量及其控制

通过分析随车起重机工作时各节伸缩臂所受最大应力,应用等应力设计原理,确定了各节伸缩臂最佳伸缩量;对各节伸缩臂伸缩量控制系统进行了设计,并对控制系统的控制器进行数学建模、算法设计、性能仿真和参数匹配。通过现场试验表明．基于等应力的最佳伸缩量能够改善随车起重机伸缩臂的受力状况,提高其工作可靠性。     

Robust control and actuator dynamics compensation for railway vehicles

A robust controller is designed for active steering of a high speed train bogie with solid axle wheel sets to reduce track irregularity effects on the vehicle’s dynamics and improve stability and curving performance. A half-car railway vehicle model with seven degrees of freedom equipped with practical accelerometers and angular velocity sensors is considered for the H_∞ control design. The controller is robust against the wheel/rail contact parameter variations. Field measurement data are used as the track irregularities in simulations. The control force is applied to the vehicle model via ball-screw electromechanical actuators. To compensate the actuator dynamics, the time delay is identified online and is used in a second-order polynomial extrapolation carried out to predict and modify the control command to the actuator. The performance of the proposed controller and actuator dynamics compensation technique are examined on a one-car railway vehicle model with realistic structural parameters and nonlinear wheel and rail profiles. The results showed that for the case of nonlinear wheel and rail profiles significant improvements in the active control performance can be achieved using the proposed compensation technique.     

Two degrees of freedom PID multi-controllers to design a mathematical driver model: experimental validation and robustness tests

This paper proposes a mathematical driver model based on PID multi-controllers having two degrees of freedom. Each PID controller making up this model is synthesised by the Ziegler–Nichols oscillation method, using the linear time invariant models which are obtained around their nominal operating points. Different PID controllers are combined using nonlinear optimisation and the H _∞ constraint. To demonstrate its robustness, it was tested on two models: a linear parameter variant model and a nonlinear four-wheel model. It was also tested in situations of high dynamic demand. The driver model showed good performance, stability and trajectory tracking. The performance tests were carried out using experimental data acquired by a Laboratory Peugeot 307 developed by INRETS-MA. This driver model was developed for an application known as ‘Itinerary Rupture DIagnosis’ (DIARI), which aims to evaluate the physical limits of a vehicle negotiating a bend. DIARI requires a tool to determine the steering commands to be applied to a vehicle model, making extrapolations with respect to speed.     

Dynamics of Pneumatic Tire Vehicles with Connected Suspension Systems

SUMMARY

A vehicle model, with 10 degrees of freedom is used to investigate the skidding conditions of any wheel of the vehicle in motion. Equations for the load transfer and equations for the pneumatic tire spring and shock absorber are derived. Parameters such as gradual cornering, U-curve cornering, the wavy road surface of different wave lengths and cases of independent and connected suspension systems are inputs to the system. The tire calculated forces and their corresponding maximum resistance forces are the outputs of the systems. A connected suspension system is found to resist skidding better than the independent suspension system. The system is non-linear, and numerical solutions are obtained.