Store-and-forward based methods for the signal control problem in large-scale congested urban road networks

The problem of designing network-wide traffic signal control strategies for large-scale congested urban road networks is considered. One known and two novel methodologies, all based on the store-and-forward modeling paradigm, are presented and compared. The known methodology is a linear multivariable feedback regulator derived through the formulation of a linear-quadratic optimal control problem. An alternative, novel methodology consists of an open-loop constrained quadratic optimal control problem, whose numerical solution is achieved via quadratic programming. Yet a different formulation leads to an open-loop constrained nonlinear optimal control problem, whose numerical solution is achieved by use of a feasible-direction algorithm. A preliminary simulation-based investigation of the signal control problem for a large-scale urban road network using these methodologies demonstrates the comparative efficiency and real-time feasibility of the developed signal control methods.     

Multiple USV cooperative algorithm method for hunting intelligent escaped targets北大核心CSCD

[目的]针对无人艇协同围捕过程中逃跑目标具备智能性,现有无人艇策略难以围捕成功的问题,提出一种基于双层切换策略的多无人艇协同围捕算法。[方法]第1层围捕策略采用改进势点法,以无人艇与势点的总直线距离最小为优化目标,采用匈牙利算法为无人艇动态分配势点,并采用人工势场法实现无人艇的协同避碰;第2层围捕策略利用了阿波罗尼奥斯圆的性质,在两艘无人艇前往逃跑目标的目标点进行拦截,剩余无人艇运动方向保持与逃跑目标相同,以不断缩紧包围区域;为应对逃跑目标不同的逃跑方式,第1层围捕策略和第2层围捕策略可互相转化。[结果]仿真实验表明,该算法相较于顺序分配势点算法和极角分配势点算法,围捕时间更少或持平,证明了该算法的有效性和先进性。[结论]该多无人艇协同双层围捕算法,对具备典型智能性的逃跑目标具有围捕效果。     

Assimilation of sea surface temperature in the POL Coastal Ocean Modelling System

A one-dimensional scheme is used to assimilate satellite Sea Surface Temperature data into the Proudman Oceanographic Laboratory Coastal Ocean Modelling System, set up in the Irish Sea with a fine resolution ( 1.8 km). The capabilities of the assimilation scheme are investigated using two different sets of satellite data, of lower and similar resolution to that of the model respectively. Comparison of results with independent data show that assimilation improves the modelled Sea Surface Temperature, but does not address model representation of the temperature vertical structure. It is concluded that for the Irish Sea and at the scales resolved by the model, the assimilation problem cannot be approached in a one-dimensional framework. It is also pointed out that forecast error needs to account explicitly for errors in the representation of the vertical structure of the thermal field.Three-dimensional methods that are suited for coastal systems are then suggested.     

挟沙水流引起底床冲淤变化的数值模拟

本模型为垂向二维数学模型,以修正的NS方程为基础,采用粒子Level Set方法和对流扩散方程分别模拟自由水面和悬沙运动,根据底床物质质量平衡的原则计算底床变形,可模拟水流引起的底床冲淤变化.该模型将水流模型扩展到泥沙运动领域,以二相流概念简化自由水面边界条件,模拟悬沙、底沙和底床变形;采用固定的笛卡尔坐标,不需重新划...     

夯管帷幕工法在隧道施工中的应用

夯管帷幕施工工法是一种全新的隧道施工工法。详细介绍夯管帷幕工法的原理、特点、施工工艺及施工技术要点等。     

TRAXX——提高铁路运输竞争能力的集成式机车平台

庞巴迪公司交通运输部按照运用部门和市场准入的要求,根据在交流机车和多电流制机车上证实是可靠的系统开发了新一代机车平台TRAXX.该机车平台采用了新的总体布置设计,使交流、直流、多电流制和内燃机车有相同的总体布置,实现了机车历史上所有各种机车的通用性,运用部门也得到了此前不能实现的最佳协作和高度的灵活性.     

Novel coordinated algorithm for Traction Control System on split friction and slope road

A Traction Control System (TCS) is used to avoid excessive wheel-slip via adjusting active brake pressure and engine torque when vehicle starts fiercely. The split friction and slope of the road are complicated conditions for TCS. Once operated under these conditions, the traction control performance of the vehicle might be deteriorated and the vehicle might lack drive capability or lose lateral stability, if the regulated active brake pressure and engine torque can’t match up promptly and effectively. In order to solve this problem, a novel coordinated algorithm for TCS is brought forward. Firstly, two brake controllers, including a basic controller based on the friction difference between the two drive wheels for compensating this difference and a fuzzy logic controller for assisting the engine torque controller to adjust wheel-slip, are presented for brake control together. And then two engine torque controllers, containing a basic PID controller for wheel-slip control and a fuzzy logic controller for compensating torque needed by the road slope, are built for engine torque control together. Due to the simultaneous and accurate coordination of the two regulated variables the controlled vehicle can start smoothly. The vehicle test and simulation results on various road conditions have testified that the proposed method is effective and robust.     

Application of Optimal Control Theory to Inverse Simulation of Car Handling

The application of Optimal Control Theory to time-optimal inverse simulation of car handling was investigated. Time-optimal inverse simulation of car handling involves the calculation of driver actions required to perform specified manoeuvres, in as short a time as possible. Driver actions consist of time-histories of front wheel steer rate and longitudinal force. Optimal time-histories of these quantities were calculated using the Gradient method after formulating the problem as one of optimal control. Simulation results are presented for two different cars performing similar lane-changes. These results show significant differences in necessary driver actions for different cars and demonstrate the suitability of the approach taken.     

碎石基层的塑性变形对混凝土路面力学行为的影响

在这项研究中,通过与旋转硬化概念的结合来修正基于广义SMP准则的原始改良Cam-Clay模型,模拟在水泥混凝土板下碎石基层的塑性变形的发展,称之为旋转硬化Cam-Clay模型.模型通过预测塑性变形累计曲线和对碎石基层循环加载的三轴压缩试验得到的试验值相比较来确认.模型成功地预测了试件塑性变形的发展,塑性变形在一开始时迅速增长,此后增长的速率减小.该模型与三维有限元模型 (3DFEM)结合,在足尺试验路面上进行模拟试验.试验发现,水泥混凝土路面的弯沉值随着荷载重复次数的增加而增加,表明在水泥混凝土板下由于基层的塑性变形而产生了缝隙.通过引入等效荷载次数的概念来模拟在合理的计算时间内施加大量循环荷载的塑性回应.模拟结果和试验数据比较表明该概念是有效的.此外,调查了由于基层缝隙而引起的水泥混凝土路面的力学响应(变形,压力以及弯沉).     

TLA改性沥青的高温流变性能研究

采用动态力学分析方法对基质沥青和TLA改性沥青的高温动态流变性能进行研究,测定了一定温度和频率范围内的动态流变性能参数,并通过分析TLA掺量不同的改性沥青的动态性能参数变化规律来分析TLA对沥青的流变性能的影响,结果表明：加入TLA后沥青复数模量增大,相位角减小,沥青的车辙因子相应增大.