Minimum Time Overtaking Problem of Vehicle Handling Inverse Dynamics Based on Two Kinds of Safe Distances

Overtaking accidents caused by improper operations performed by a driver occur frequently. However, most stud?ies on overtaking safety have neglected research into driver control input. A novel method is proposed to obtain the driver control input during the overtaking process. Meanwhile, to improve the safety of overtaking, two types of safe distances, and the time of the overtaking are considered. Path constraints are established when considering the two types of safe distances. An optimal control model is established to solve the minimum time maneuver under multiple constraints. Using the Gauss pseudospectral method, the optimal control problem is converted into a nonlinear pro?gramming problem, which is then solved through sequential quadratic programming(SQP). In addition, the e ective?ness of the proposed method is verified based on the results of a Carsim simulation. The simulation results show that by adopting an inverse dynamics method to solve the manipulation problem of the vehicle’s minimum overtaking time, the manipulation capability of a vehicle in completing an overtaking safely within the minimum time can be obtained. This method can provide a reference for research into the active safety of manned and unmanned vehicles.

A Simple Traffic Model Including Possibility of Overtaking

Previously we examined different parameters relevant to traffic flow. For illustrative purposes we considered a specific case of approaching a city. The case involves a traffic light where one continues on the main road, into which additional cars are entering at the light. At this intersection an alternative route begins, which is longer but into which no additional cars are entering. In addition to the “Slow to move” model we add here a possibility of “overtaking”, which is quite artificial as our model is one dimensional. Still we think that this gives fair results.

Target Vehicle Selection Algorithm for Adaptive Cruise Control Based on Lane-changing Intention of Preceding Vehicle

To improve the ride comfort and safety of a traditional adaptive cruise control(ACC)system when the preceding vehicle changes lanes,it proposes a target vehicle selection algorithm based on the prediction of the lane-changing intention for the preceding vehicle.First,the Next Generation Simulation dataset is used to train a lane-changing intention prediction algorithm based on a sliding window support vector machine,and the lane-changing intention of the preceding vehicle in the current lane is identified by lateral position offset.Second,according to the lane-changing intention and collision threat of the preceding vehicle,the target vehicle selection algorithm is studied under three different conditions:safe lane-changing,dangerous lane-changing,and lane-changing cancellation.Finally,the effectiveness of the proposed algorithm is verified in a co-simulation platform.The simulation results show that the target vehicle selection algorithm can ensure the smooth transfer of the target vehicle and effectively reduce the longitudinal acceleration fluctuation of the subject vehicle when the preceding vehicle changes lanes safely or cancels their lane change maneuver.In the case of a dangerous lane change,the target vehicle selection algorithm proposed in this paper can respond more rapidly to a dangerous lane change than the target vehicle selection method of the traditional ACC system;thus,it can effectively avoid collisions and improve the safety of the subject vehicle.

A new traffic model on compulsive lane-changing caused by off-ramp

In the field of traffic flow studies, compulsive lane-changing refers to lane-changing （LC） behaviors due to traffic rules or bad road conditions, while free LC happens when drivers change lanes to drive on a faster or less crowded lane. LC studies based on differential equation models accurately reveal LC influence on traffic environment. This paper presents a second-order partial differential equation （PDE） model that simulates both compulsive LC behavior and free LC behavior, with lane-changing source terms in the continuity equation and a lane-changing viscosity term in the momentum equation. A specific form of this model focusing on a typical compulsive LC behavior, the ＇off-ramp problem＇, is derived. Numerical simulations are given in several cases, which are consistent with real traffic phenomenon.

Modelling of vehicle interaction behavior during discretionary lane-changing preparation process on freeway

In order to increase the accuracy of microscopic traffic flow simulation,two acceleration models are presented to simulate car-following behaviors of the lane-changing vehicle and following putative vehicle during the discretionary lanechanging preparation( DLCP) process, respectively. The proposed acceleration models can reflect vehicle interaction characteristics. Samples used for describing the starting point and the ending point of DLCP are extracted from a real NGSIM vehicle trajectory data set. The acceleration model for a lanechanging vehicle is supposed to be a linear acceleration model.The acceleration model for the following putative vehicle is constructed by referring to the optimal velocity model,in which optimal velocity is defined as a linear function of the velocity of putative leading vehicle. Similar calibration,a hypothesis test and parameter sensitivity analysis were conducted on the acceleration model of the lane-changing vehicle and following putative vehicle,respectively. The validation results of the two proposed models suggest that the training and testing errors are acceptable compared with similar works on calibrations for car following models. The parameter sensitivity analysis shows that the subtle observed error does not lead to severe variations of car-following behaviors of the lane-changing vehicle and following putative vehicle.

A new traffic model with a lane-changing viscosity term

In this paper, a new continuum traffic flow model is proposed, with a lane-changing source term in the continuity equation and a lane-changing viscosity term in the acceleration equation. Based on previous literature, the source term addresses the impact of speed difference and density difference between adjacent lanes, which provides better precision for free lane-changing simulation; the viscosity term turns lane-changing behavior to a ＂force＂ that may influence speed distribution. Using a flux-splitting scheme for the model discretization, two cases are investigated numerically. The case under a homogeneous initial condition shows that the numerical results by our model agree well with the analytical ones; the case with a small initial disturbance shows that our model can simulate the evolution of perturbation, including propagation,dissipation, cluster effect and stop-and-go phenomenon.

Effects of Potential Lane-Changing Probability on Uniform Flow

In this paper, we use the car-following model with the anticipation effect of the potential lane-changing probability （Acta Mech. Sin. 24 （2008） 399） to investigate the effects of the potential lane-changing probability on uniform flow. The analytical and numerical results show that the potential lane-changing probability can enhance the speed and flow of uniform flow and that their increments are related to the density.

后发经济体在全球产业链重构中的弯道超车——历史经验及对中国的启示

全球产业链重构为后发经济体提供了弯道超车的机会,有利于其充分发挥自身的后发优势,实现本土产业链的长足发展。纵观全球产业链发展史,颠覆性的技术创新、比较优势变化和全球治理体系变革是驱动全球产业链重构的主要机制。到目前为止,全球产业链共经历了五次重构,依次伴随着美国、日本、“亚洲四小龙”、中国以及南亚和东南亚地区等相应时期后发经济体的崛起。通过研究驱动机制和后发经济体案例,本文发现后发经济体在参与全球产业链重构时,需重点关注核心技术、需求市场以及国际经贸规则等方面,从而充分发挥后发优势,实现弯道超车。基于此,中国应借鉴后发经济体在全球产业链重构中的弯道超车经验,抓住目前全球产业链重构的新发展机遇,不断推动技术进步以促进产业链升级,不断扩大内需以保障产业链安全,还应积极参与全球治理规则重构,为全球治理体系变革贡献中国方案。

基于驾驶模拟的超车仿真教学实验设计

道路交通运输专业具有多学科融合、紧密结合实践的特点,但许多交通专业课程的实践教学环节往往会受到场地大小、条件不可控、重复性差和实际道路危险性等不利因素的限制而无法顺利开展。为提升学生的实践能力与课程参与度,基于驾驶模拟技术,探讨可用于交通仿真、道路交通安全及交通行为分析等课程教学的超车仿真教学实验项目,教学实验以锻炼学生分析解决问题能力和实践操作能力为目标,详细地设计实验流程与实践教学内容,并将该实验项目在道路交通安全、交通仿真等课程的实践环节进行应用,为驾驶模拟系统在教学实验中的应用提供参考。

智能网联汽车超车路径规划方法

针对自动驾驶车辆超车路径规划的问题,本文提出改进的人工势场法并引入相对速度构建新的引力势场和斥力势场.建立道路边界势场规范行车区域,对障碍物的影响距离进行分段解决局部极值问题,将自动驾驶车辆动力学相关约束融入人工势场法建立超车路径行驶势场模型.选取重庆市内环快速路为试验路网原型,利用无人机以及定点摄像等数据采集方法进行实地调查,并采用MATLAB/Simulink,CarSim和PreScan进行联合仿真分析.实验结果表明:相比传统的人工势场法,在前车静止、前车匀速、前车减速这3种条件下的超车路径曲率分别降低了85.07%,62.69%和83.86%,横向加速度均小于0.13m/s^(2),改进后的路径规划算法可成功实现平稳超车,驾乘人员的舒适性上有显著提升.

既有地铁线非站站停列车开行方案与越行站设置协同优化研究

研究既有地铁非站站停列车开行方案和越行站设置协同优化对提高线路通过能力和运输效率具有重要意义。将非站站停列车开行方案编制与越行站设置协同考虑,出行乘客以出行OD分类,构建以企业运营成本、乘客出行成本以及列车越行成本最低为目标的既有地铁线非站站停列车开行方案优化模型,考虑线路通过能力及快车停靠等约束,依据模型特点选用遗传模拟退火算法进行模型求解。以西安地铁14号线为例验证构建模型有效性,求解结果表明:与传统的站站停运营组织模式相比,乘客总在车时间降低29.84%,企业运营成本降低4.33%,车底购置成本降低5.23%,同时讨论不同越行站位置选择对企业运营成本的影响,为轨道公司实施非站站停运营组织模式及相关车站改造提供决策支撑。

基于改进势场法的智能车超车动态路径规划

为了改进人工势场法(artificial potential field,APF)在智能车高速超车状态下规划出的轨迹规范性差、安全性得不到保障、以及路径不平滑的问题。设计用于指引智能车换道的换道引力势场,以保证换道轨迹的规范性;构建异向分布结构的障碍车斥力势场提高换道的安全性;并建立带有转向缺口的道路中心线斥力势场和设计平滑代价函数优化规划出的轨迹点,使规划出的路径更加平滑。基于线性二次型调节器(linear quadratic regulator,LQR)设计路径跟踪控制器跟踪规划出的路径。通过Simulink与Carsim联合仿真,结果表明:所改进的APF算法能规划出更加合理的路径,设计的LQR路径跟踪控制器跟踪误差趋近于零,能够较好地控制车辆完成超车换道。

高原山区双车道公路超车车道设置条件与参数

为给高原山区双车道公路超车车道的设计提供参考依据,针对高原山区双车道公路超车车道设置的几何条件、交通量条件与设置长度开展研究。通过工程实例验证了模型的有效性,进行了超车车道长度与运行速度的相关性研究。首先,结合高原山区条件的影响,从保证超车车辆驾驶人舒适度的角度出发,给出了高原山区双车道公路超车车道的最小圆曲线半径值;其次,从车辆转向安全行驶的角度出发,给出了超车车道的最大上坡和下坡坡度条件;然后,建立了双车道公路交通冲突时间与交通量、设计速度的关系模型,并给出了各设计速度下设置超车车道的交通量条件;最后,基于VISSIM仿真试验数据,利用多元非线性回归法构建了高原山区双车道公路超车车道长度模型。结果表明:在高原山区环境下,当双车道公路的设计速度分别为80,60,40 km/h时,满足设置超车车道要求路段的交通量应大于392,364,318 pcu/h;平面圆曲线半径应大于610,370,200 m;下坡方向的最大纵坡分别为―2.4%,―2.7%,―3.2%;上坡方向的最大纵坡分别为2.6%,3.0%,3.5%;在同一交通量条件下,随着双车道公路超车车道长度的增加,小客车的平均运行速度呈现出逐渐增大的趋势,当超车车道长度达到一定值时,平均运行速度维持在80 km/h,不再发生明显变化。

基于多目标优化的高速超车轨迹规划

为保障高速超车规划过程中的安全,同时提升轨迹的舒适性,笔者提出一种基于多目标的高速超车轨迹规划算法。该算法在可行凸空间的基础上求解出高速超车边界条件,再通过安全超车策略对超车行为的可行性进行分析,随后根据建立的超车轨迹规划目标函数和舒适性优化函数对轨迹的平顺性和乘坐的舒适性等目标进行优化,并且算法实时规划轨迹直至超车行为完成。为验证该算法的有效性,利用Prescan和MATLAB/Simulink构建联合仿真平台,对所设计的两种常见超车场景进行验证分析。仿真结果表明:在匀速超车以及加速超车场景下,相较于单目标优化,经多目标优化的超车轨迹的横向位移峰值、横向加速度峰值、横摆角速度峰值、曲率峰值,以及车速峰值的优化效果都获得了提升,有效的提高了所规划超车轨迹的舒适性和安全性。

桥上轿车并行超车的风致安全评价及横向运动控制

为厘清并行超车过程中“风-车-桥”的气动交互干扰及其对轿车侧风稳定性的影响,采用空气动力学与系统动力学耦合方法建立了侧风环境下桥上轿车分别超轿车和货车的风致安全评价模型,揭示了轿车超车过程中气动侧力和气动横摆力矩的变化规律及作用机理,基于线性二次最优控制的路径跟踪模型分析了轿车超车过程中有、无控制作用时侧偏运动和横摆运动的差异。结果表明,“风-车-桥”气动交互干扰形成的高速低压区和低速低压区对行车安全有显著影响,影响程度与被超车类型及所在车道有关:轿车超轿车时,在迎风侧第1车道超其他车道轿车时为较危险工况;轿车超货车时,在迎风侧第1车道超其他车道货车及在第2车道超第1车道货车时为较危险工况。研究结果可为提升桥梁风致行车安全能力提供参考。

二级公路“2+1”车道超车段长度设置及仿真

二级公路在中国公路网中占有重要地位,一般采用双向两车道布局。然而,当交通流量达到一定水平时,二级公路的双车道布局模式很难满足车辆在行驶过程中的超车需求。“2+1”车道布局为上述问题提供了很好的解决方案,但如何确定最佳超车段长度已成为一个新问题。以“2+1”车道二级公路为研究对象,通过采用微观交通仿真技术,以延误和速度为评价指标,针对不同的流量和车型组合对超车段长度开展了仿真分析和评价,结果表明:在“2+1”车道布局模式下,超车段的通行效率有显著提高,超车段的最佳长度为1.2 km。

考虑船间效应和操纵性能的内河船舶追越风险模型及应用

针对内河在航船舶追越过程中碰撞事故频发的问题,构建考虑船间效应和操纵性能的内河船舶追越风险模型。对内河在航船舶追越过程进行情景分析,从纵向和横向距离两个方面综合考虑船舶追越风险。引入船舶纵向安全距离模型和紧急转舵距离,提出不同危险局面下的纵向距离计算方法。考虑船间效应和船舶保向性,根据力和力矩方程,提出不同会遇时刻的横向距离计算方法。构建基于模糊逻辑的内河船舶追越风险模型,选取100组长江典型追越案例验证模型的可行性。

二级公路“2+1”车道布局模式关键设计参数研究

采用“2+1”车道布局有利于解决现状双车道二级公路车辆排队、强行超车等问题,但由于目前国内尚未针对“2+1”车道设计理论开展系统研究,其工程实践非常欠缺。通过对公路设计规范、国外“2+1”车道设计等资料的分析,确定了二级公路“2+1”车道布局概念模式,并运用交通工程与交通安全方法,对“2+1”车道二级公路超车段、合流与分流渐变段长度等关键参数开展了理论分析,然后运用交通仿真手段,采用效率评价指标对理论分析结果进行测试、调优,最终确定了“2+1”车道设计最优参数及适应交通量。其研究成果能为“2+1”车道在我国二级公路上的应用提供技术参考,有望丰富我国二级公路设计建设相关标准。

浮泥层对船船干扰影响的数值计算

针对浮泥层对船船干扰的影响问题,通过求解RANS方程对浮泥水域中追越船与被追越船间的水动力干扰问题进行数值模拟.对比分析了有无浮泥时追越船与被追越船所受力和力矩特点,讨论了在浮泥水域中不同水深吃水比、富裕水深及航速比变化对两船所受力和力矩的影响.结果表明:浮泥层会扩大船船干扰的范围;追越船所受力和力矩及被追越船所受力矩各极值随富裕水深的增大而减小;水深吃水比一定时,追越船所受力和力矩各极值随浮泥厚度的增大而增大;被追越船所受力和力矩各极值随航速比的增大而减小;船尾散波发散角度随船速的增大而减小.

市域快轨快慢车模式越行节省时间研究

不同于地铁制式,市域快轨是轨道交通建设为满足通勤化、大运量、快速度需求发展到一定阶段产生的新型式,其快慢车运营模式势在必行。为此,在既有研究的基础上,综合考虑运营模式、越行速度、越行站站型、道岔型号等因素,对市域快轨快慢车运营模式下的越行节省时间计算方法展开研究,形成计算方法。以国内某市域快轨为基础建立仿真模型,通过OpenTrack仿真技术验证理论计算结果,得到如下结论:当越行速度介于60~120km/h之间时,追踪模式下快车跳站运营,每跳一站相比慢车停站的节省时间(含慢车停站时间)介于37~55s;越行模式下快车越行运营,每越行一站相比慢车停站的节省时间(含慢车停站时间)介于69~87s。与仿真结果相比,理论计算平均误差不超过3%。研究成果可为市域快轨快慢车运营时间效益分析提供参考。