Estimation of delay variability at signalized intersections for urban arterial performance evaluation

Urban arterial performance evaluation has been broadly studied, with the major focus on average travel time estimation. However, in view of the stochastic nature of interrupted flow, the ability to capture the characteristics of travel time variability has become a critical step in determining arterial level of service (LOS). This article first presents a stochastic approach that integrates classic cumulative curves and probability theories in order to investigate delay variability at signalized intersections, as a dominant part of the link travel time variability. This serves as a basis for arterial travel time estimation, which can be obtained through a convolution of individual link travel time distributions. The proposed approach is then applied in the estimation of travel time along one arterial in Shanghai, China, with abundant automatic vehicle identification (AVI) data sources. The travel time variability is evaluated thoroughly at 30-min intervals, with promising results achieved in comparison to the field measurements. In addition, the estimated travel time distributions are utilized to illustrate the probability of multiple LOS ranges, namely, reliability LOS. The results provide insights into how we might achieve a more reliable and informative understanding of arterial performance.     

单交叉口公交信号优先控制策略建模研究

为研究公交信号优先策略对交叉口公交车及社会车辆的影响,建立公交信号优先控制模型及延误模型,以采取公交优先方式后交叉口所有车辆的人总延误减小为控制目标,引入效益指数PI,以信号交叉口优先相位获得的效益与非优先相位损失效益的差值来衡量整体效益,使得每一次采取的公交优先策略都能提高信号交叉口的整体效益。结果表明:在信号交叉口采取信号优先控制策略后,交叉口车辆的人总延误显著降低。本研究成果对其他信号优先控制方式模型、交叉口群公交优先协调控制等具有一定的参考价值和理论意义。     

基于人均延误的公交优先信号交叉口配时研究

以交叉口人均延误最小为目标,考虑公交专用道影响因素,利用延误偏差优度指数建立信号配时优化模型。结合实例,实现定时控制交叉口参数确定过程,并得到参数与延误偏差优度指数的关系。该配时方案能有效减少人均延误,为进一步发展公交优先及提高交叉口通行能力提供理论依据。     

动态载荷识别的自适应延迟逆模型方法

为减小载荷识别问题对原系统先验知识的依赖,采用系统的自适应延迟逆模型识别时域载荷。采用自适应算法辨识延迟逆模型,代替了一般识别方法中的系统特性矩阵求逆过程,避免了病态问题。随后将工作状态下的响应作为逆模型的输入,则其输出就是时域载荷的延迟估计。通过对两端简支梁结构进行载荷识别的仿真研究,以及对双层隔振试验台架的试验研究,识别了稳态激励和瞬态激励,验证了该方法的有效性。该方法不需要了解系统的数学模型及参数,因此能够应用于工程实践中。     

船舶液压起重机延迟反馈吊重消摆控制

由于操纵和工作环境的变化,起重机的吊重在工作过程中会产生摆动,这种摆动降低了起重机的工作效率和安全性能。文章以集美大学轮机工程实验中心船舶液压起重机为研究对象,采用机电液仿真建模技术及拉格朗日方程,在MATLAB Simulink仿真软件平台上,建立起重机操作液压系统及吊重摆动模型,采用与试验数据对比的方法对所建立的模型进行验证。设计基于吊重摆动位置延迟反馈的控制器,通过将延迟反馈信号叠加到操作信号上的方法实现吊重的消摆控制。结果表明,在各种操作情况下,延迟反馈控制器均能很好地抑制吊重的摆动。     

隧道爆破信号主分量特征提取与毫秒延期识别研究

为了准确揭示隧道爆破振动信号所包含的反映爆破特征参数的重要信息,通过EMD分解与交叉小波变换组合分析方法对实测爆破信号进行分析,得到各分量与原信号的相关性系数,从而准确判别出信号的主分量。再依据相关性系数对包含主分量在内的相关分量重组并进行Hilbert变换取模值,精确识别出隧道采用的各段别雷管的毫秒延期时间。结果表明： 组合方法确定的主分量及相关分量重组信号能够突出爆破信号的主要特征,对隧道爆破信号的分析效果好。     

航班快速恢复建模与仿真研究

随着民用航空的发展与竞争,航班延误不仅影响航空飞行的安全与正常,更与航空公司的运营效率、运营成本及乘客利益息息相关。针对某一恶劣天气影响,对某公司受影响航班进行重新调配,考虑到航班的备降、盘旋等待、延误、取消等多种状态,以总成本最小为目标函数,建立航班快速恢复模型,通过MATLAB运用遗传算法设计航班恢复算法进行求解,得出最经济的航班恢复方案。     

网络环境下无人水面艇航向控制器设计

无人水面艇自主航行中受到外部环境干扰及在控制中心-执行器网络通道中存在网络诱导特性(如网络诱导时延、数据丢包等)的影响,会降低系统性能,影响航向控制系统的稳定性.为了能使无人艇按照设定航向快速、稳定地航行,提出一种基于网络的无人艇航向控制策略.首先,建立基于网络的无人艇航向控制系统模型.基于这个模型,运用Lyapunov稳定性理论和凸分析方法导出能使网络环境下无人水面艇航向控制系统渐进稳定的控制律,并设计基于网络的航向控制器.通过仿真验证所提出方法和设计控制器的有效性.     

An exact modelling of the uniform control traffic delay in undersaturated signalized intersections

The average delay experienced by vehicles at a signalized intersection defines the level of service (LOS) at which the intersection operates. A major challenge in this regard is the ability to accurately estimate all the components underlying the overall control delay, including the uniform, incremental and initial queue delays. This paper tackles this challenging task by proposing a novel exact model of the uniform control delay component with a view to enhancing the accuracy of the existing approximate models, notably, the one reported in the Highway Capacity Manual 2010. Both graphical and analytical proofs are employed to derive exact closed‐form expressions for the uniform control delay at undersaturated signalized intersections. The high degree of accuracy of the proposed models is analysed through extensive simulations to demonstrate their abilities to exactly characterize the performance of real‐life intersections in terms of the resulting vehicle delay. Unlike the existing widely adopted uniform delay models, which tend to overestimate the LOS of real‐life intersections, the delay models introduced in this paper have the merit of exactly capturing such a LOS. Copyright © 2016 John Wiley & Sons, Ltd.     

Modeling delay at signalized intersections with channelized right‐turn lanes considering the impact of blockage

This paper presents a probabilistic delay model for signalized intersections with right‐turn channelization lanes considering the possibility of blockage. Right‐turn channelization is used to improve the capacity and to reduce delay at busy intersections with a lot of right‐turns. However, under heavy traffic conditions the through vehicles will likely block the channelization entrance that accrues delay to right‐turn vehicles. If the right‐turn channelization gets blocked frequently, its advantage in reducing the intersection delay is neglected and as a result the channelization lane becomes inefficient and redundant. The Highway Capacity Manual (HCM) neglects the blockage effect, which may be a reason for low efficiency during peak hours. More importantly, using HCM or other standard traffic control methods without considering the blockage effects would lead to underestimation of the delay. To overcome this issue, the authors proposed delay models by taking into account both deterministic and random aspects of vehicles arrival patterns at signalized intersections. The proposed delay model was validated through VISSIM, a microscopic simulation model. The results showed that the proposed model is very precise and accurately estimates the delay. In addition, it was found that the length of short‐lane section and proportion of right‐turn and through traffic significantly influence the approach delay. For operational purposes, the authors provided a step‐by‐step delay calculation process and presented approach delay estimates for different sets of traffic volumes, signal settings, and short‐lane section lengths. The delay estimates would be useful in evaluating adequacy of the current lengths, identifying the options of extending the short‐lane section length, or changing signal timing to reduce the likelihood of blockage. Copyright © 2016 John Wiley & Sons, Ltd.