H∞控制在汽车电子稳定性程序中的应用

文章从理论上证明了电子稳定性程序控制ESP(electronic stability program)对汽车稳定性的明显作用。通过数字仿真分析表明,该控制方法能有效改善车辆转向时的侧偏角和横摆率的响应特性,更好地实现了驾驶员的驾驶意图。     

基于Adams和Matlab联合的汽车悬架系统仿真分析

伴随着虚拟样机技术的不断发展,虚拟物理模型与控制模型联合仿真技术日趋成熟。文中利用ADAMS软件,建立了二分之一车体四自由度汽车主动悬架的虚拟模型。通过集成车辆主动悬架系统的动力学方程,搭建了基于ADAMS和MATLAB联合的汽车悬架系统仿真平台。在此基础上,比较分析了某轿车汽车车身垂直加速度响应和车身俯仰角加速度响应,该模拟结果与文献[1]数学模型的结果基本吻合,从而验证了系统仿真平台正确性。     

基于响应面法和蒙特卡洛法的公路路堑边坡稳定性可靠度分析

为了研究公路路堑边坡稳定性,分析边坡的稳定状态,文章以某路堑边坡为例,基于可靠度理论,采用响应面法和蒙特卡洛法,对边坡稳定性敏感因素中的粘聚力和内摩擦角两个岩土参数进行了分析。分析结果表明:响应面法和蒙特卡洛法所得可靠度指标存在一定误差,其计算值分别为2.966 4和3.252 6;粘聚力及内摩擦角均值与可靠度指标呈正相关,两者变异系数、相关系数与可靠度指标呈负相关。     

PU改性沥青混合料路用性能试验研究

文章利用聚氨酯(PU)与基质沥青、粗细集料制备出一种PU改性沥青混合料,对其高温稳定性、低温抗裂性以及水稳定性进行测试分析,并评价其应用于道路的可行性。结果表明：随着聚氨酯(PU)添加量的增多,改性沥青的动稳定度越高,高温稳定性越好;聚氨酯(PU)可使改性沥青混合料的弯拉应变值提高,且随着聚氨酯(PU)添加量的提高,其弯拉应变值同步提高,低温抗裂性能变好;PU改性沥青混合料的残留稳定度较高,抗水损害性能较好,满足路用标准。     

用经济、技术手段为“节能减排”拉下双重闸门 访福建省汽车运输总公司总经理王闽寅

<正>对于汽车运输企业来说,节能减排不仅仅是响应国家的大政方针,还关系着企业的经济效益。如何把利国利民利己的节能减排工作做好,成为各个企业的重点工作。在交通运输行业第二批节能减排典型示范项目中,福建省汽车运输总公司的"严格营运车辆准入,优化车辆技术结构"项目从影响汽车燃料消耗量的主要因素,即车辆技术、运行环境及汽车运用三大方面入手,为汽车运输企业如何降低燃料消耗探索出了一条值得借鉴的途径。     

基于TruckSim的重型清障车操纵稳定性分析

国内清障车主要使用的是载货汽车的二类汽车底盘,这种底盘在整车的结构布置和承力方式上有许多不满足清障车专用作业装置的布置需求。本文以重型清障车的操纵稳定性为研究目标,基于TruckSim软件建立某款重型清障车工程样车的整车模型,参照《GB/T 6323-2014汽车操纵稳定性试验方法》对汽车进行稳定性仿真试验,选取不同质心高度和质心纵向位移进行开环评价和闭环评价对比分析。结果表明在原设计参数的基础上降低车辆的质心高度和前移质心纵向位移,对车辆的操纵稳定性具有一定的提高。     

破碎岩层位置对隧道稳定性的影响研究

为揭示破碎岩层位置对隧道稳定性的影响规律,文章以某节理裂隙岩体隧道为研究对象,根据破碎岩层位置的不同分别建立6个计算模型,采用离散元软件UDEC对各个模型进行仿真模拟,并对比分析破碎岩层不同位置下的隧道开挖后应力和位移响应云图。结果表明:当破碎岩层位移隧道中线以上时,对隧道稳定性影响最大;当破碎岩体层位于隧道中心以下,对隧道稳定性影响较小。     

钢渣沥青混合料早期性能的时变规律研究

在钢渣沥青混合料路面成型早期,裹覆钢渣集料的结构沥青和自由沥青仍处于变化之中,钢渣沥青混合料早期性能也随时间发生变化。文章通过沥青浸渍实验对比分析钢渣、石灰岩碎石对沥青的吸收特性随时间变化的规律,并将沥青混合料试件放置不同时间后进行室内车辙试验、低温弯曲小梁试验、冻融劈裂试验,研究不同钢渣掺量(0%、50%、100%)沥青混合料的高温稳定性、低温抗裂性、水稳定性随时间变化的规律。结果表明:钢渣对沥青的瞬时吸收量约为石灰岩碎石的10倍,且钢渣对沥青的吸收量随时间增大,约10d后趋于稳定;钢渣掺量越高,最佳沥青用量越高,新成型试件的高温稳定性、低温抗裂性、水稳定性越好,但随着试件放置时间增加,低温抗裂性和水稳定性衰退。     

海底沉管隧道管段海上系泊方式研究

海底沉管隧道管段海上系泊阶段的结构运动响应及布缆方式,直接影响其水上施工的安全性和经济性。针对某沉管隧道管段系泊工程,文章利用基于三维势流理论的水动力软件AQWA建立管段海上系泊仿真模型,分别对五种不同的系泊方式进行时,频域分析,探讨了布缆方式对沉管管段运动响应及缆索受力的影响。结果表明:管段在高频区域内稳定性较好,响应幅值很小;四缆系泊方式在实际工程中不可采用;八缆系泊方式较安全;在海况较好的情况下,可以采用更加经济的六缆系泊方案。     

汽车ESP对公路交通安全的影响及应用研究

文章通过对汽车ESP系统控制原理和公路交通安全的影响效果分析,说明汽车ESP相比被动保护驾驶员和乘客的安全带和安全气囊而言,其能够快速识别出汽车不稳定的行驶趋势,主动地帮助驾驶员进行操控车辆,最大限度地减少车辆侧撞的风险,提高车辆在公路行驶的稳定性和安全性,从而使更多汽车厂商和驾驶员意识到ESP对公路交通安全的重要性。同时对ESP自诊断技术加以分析说明,为汽车维修技术人员提供借鉴和参考。     

A new strategy for minimum usage of external yaw moment in vehicle dynamic control system

Due to the loss of vehicle directional stability in emergency maneuvers, a new complete desired model for vehicle handling based on the linear two-degrees-of-freedom (2DOF) model and tire/road conditions is presented to be tracked by the direct yaw moment control (DYC) system. In order to maintain the vehicle actual motions, yaw rate and side-slip angle, close to the proposed desired responses without excessively large external yaw moment, a complete linear quadratic (LQ) optimal problem is formulated and its analytical solution is obtained. Here, the derived control law is evaluated and its different versions are discussed. It is shown that the side-slip tracking by DYC is more effective than the yaw rate control to stabilize vehicle motions in nonlinear regimes. Also, optimal property of the control law provides the possibility of reducing the external yaw moment as low as possible, at the cost of some admissible tracking errors. Simulation studies of vehicle handling, with and without control, have been conducted using a full nonlinear vehicle dynamic model. The results, obtained during various maneuvers, indicate that when the proposed optimal controller is engaged with the model, improvements in the handling performance through a reduced external yaw moment can be acquired.     

Incident dispatching,clearance and delay

This paper models response times and delays for highway incidents, accounting for spacing between interchanges and the time penalty for changing directions, enabling a response vehicle to reach an incident on the opposite side of the highway. A fundamental question in dispatching incident crews is whether to send the closest vehicle that is currently available or to wait for another vehicle to become available that is even closer. Waiting for a closer vehicle is advantageous because service time is effectively reduced, adding to capacity and providing stability at higher levels of utilization. But waiting for a vehicle to become available adds uncertainty, which contributes to expected traffic delay. As a consequence, any reasonably robust dispatch strategy must provide for a hybridization of the two objectives, trading-off greater certainty in response time against stability at higher utilization levels.     

Intelligent cruise control systems and traffic flow stability

There are two kinds of stability associated with traffic flow problems – string stability (or car-following stability) and traffic flow stability. We provide a clear distinction between traffic flow stability and string stability, and such a distinction has not been recognized in the literature, thus far. String stability is stability with respect to intervehicular spacing; intuitively, it ensures the knowledge of the position and velocity of every vehicle in the traffic, within reasonable bounds of error, from the knowledge of the position and velocity of a vehicle in the traffic. String stability is analyzed without adding vehicles to or removing vehicles from the traffic. On the other hand, traffic flow stability deals with the evolution of traffic velocity and density in response to the addition and/or removal of vehicles from the flow. Traffic flow stability can be guaranteed only if the velocity and density solutions of the coupled set of equations is stable, i.e., only if stability with respect to automatic vehicle following and stability with respect to density evolution is guaranteed. Therefore, the flow stability and critical capacity of any section of a highway is dependent not only on the vehicle following control laws and the information used in their synthesis, but also on the spacing policy employed by the control system. Such a dependence has practical consequences in the choice of a spacing policy for adaptive cruise control laws and on the stability of the traffic flow consisting of vehicles equipped with adaptive cruise control features on the existing and future highways. This critical dependence is the subject of investigation here.     

Influence of connected and autonomous vehicles on traffic flow stability and throughput

The introduction of connected and autonomous vehicles will bring changes to the highway driving environment. Connected vehicle technology provides real-time information about the surrounding traffic condition and the traffic management center’s decisions. Such information is expected to improve drivers’ efficiency, response, and comfort while enhancing safety and mobility. Connected vehicle technology can also further increase efficiency and reliability of autonomous vehicles, though these vehicles could be operated solely with their on-board sensors, without communication. While several studies have examined the possible effects of connected and autonomous vehicles on the driving environment, most of the modeling approaches in the literature do not distinguish between connectivity and automation, leaving many questions unanswered regarding the implications of different contemplated deployment scenarios. There is need for a comprehensive acceleration framework that distinguishes between these two technologies while modeling the new connected environment. This study presents a framework that utilizes different models with technology-appropriate assumptions to simulate different vehicle types with distinct communication capabilities. The stability analysis of the resulting traffic stream behavior using this framework is presented for different market penetration rates of connected and autonomous vehicles. The analysis reveals that connected and autonomous vehicles can improve string stability. Moreover, automation is found to be more effective in preventing shockwave formation and propagation under the model’s assumptions. In addition to stability, the effects of these technologies on throughput are explored, suggesting substantial potential throughput increases under certain penetration scenarios.     

Stability analysis on a dynamical model of route choice in a connected vehicle environment

Research on connected vehicle environment has been growing rapidly to investigate the effects of real-time exchange of kinetic information between vehicles and road condition information from the infrastructure through radio communication technologies. A fully connected vehicle environment can substantially reduce the latency in response caused by human perception-reaction time with the prospect of improving both safety and comfort. This study presents a dynamical model of route choice under a connected vehicle environment. We analyze the stability of headways by perturbing various factors in the microscopic traffic flow model and traffic flow dynamics in the car-following model and dynamical model of route choice. The advantage of this approach is that it complements the macroscopic traffic assignment model of route choice with microscopic elements that represent the important features of connected vehicles. The gaps between cars can be decreased and stabilized even in the presence of perturbations caused by incidents. The reduction in gaps will be helpful to optimize the traffic flow dynamics more easily with safe and stable conditions. The results show that the dynamics under the connected vehicle environment have equilibria. The approach presented in this study will be helpful to identify the important properties of a connected vehicle environment and to evaluate its benefits.     

Vehicle detection grammars with partial occlusion handling for traffic surveillance

Traffic surveillance is an important topic in intelligent transportation systems (ITS). Robust vehicle detection is one challenging problem for complex traffic surveillance. In this paper, we propose an efficient vehicle detection method by designing vehicle detection grammars and handling partial occlusion. The grammar model is implemented by novel detection grammars, including structure, deformation and pairwise SVM grammars. First, the vehicle is divided into its constitute parts, called semantic parts, which can represent the vehicle effectively. To increase the robustness of part detection, the semantic parts are represented by their detection score maps. The semantic parts are further divided into sub-parts automatically. The two-layer division of the vehicle is modeled into a grammar model. Then, the grammar model is trained by a designed training procedure to get ideal grammar parameters, including appearance models and grammar productions. After that, vehicle detection is executed by a designed detection procedure with respect to the grammar model. Finally, the issue of vehicle occlusion is handled by designing and training specific grammars. The strategy adopted by our method is first to divide the vehicle into the semantic parts and sub-parts, then to train the grammar productions for semantic parts and sub-parts by introducing novel pairwise SVM grammars and finally to detect the vehicle by applying the trained grammars. Experiments in practical urban scenarios are carried out for complex traffic surveillance. It can be shown that our method adapts to partial occlusion and various challenging cases.     

Route design for last-in,first-out deliveries with backhauling

The retail route design problem extends the capacitated vehicle routing problem with time windows by introducing several operational constraints, including order loading and delivery restrictions (last-in, first-out), order-dependent vehicle capacity, material handling limits at the warehouse, backhauling, and driving time bounds. In this paper, the problem is modeled on a directed network for an application associated with a major grocery chain. Because the corresponding mixed-integer program proved too difficult to solve with commercial software for real instances, we developed a greedy randomized adaptive search procedure (GRASP) augmented with tabu search to provide solutions. Testing was done using data sets provided Kroger, the largest grocery chain in the US, and benchmarked against a previously developed column generation algorithm. The results showed that cost reductions of $4887 per day or 5.58% per day on average, compared to Kroger’s corresponding solutions.     

The kinematic wave model with finite decelerations: A social force car-following model approximation

This paper derives a five-parameter social force car-following model that converges to the kinematic wave model with triangular fundamental diagram. Analytical solutions for vehicle trajectories are found for the lead-vehicle problem, which exhibit clockwise and counter-clockwise hysteresis depending on the model’s parameters and the lead vehicle trajectory. When coupled with a stochastic vehicle dynamics module, the model is able to reproduce periods and amplitudes of stop-and-go waves, as reported in the field. The model’s stability conditions are analysed and its trajectories are compared to real data.