排序方式: 共有66条查询结果,搜索用时 31 毫秒
1.
Estimation of urban network link travel times from sparse floating car data (FCD) usually needs pre-processing, mainly map-matching and path inference for finding the most likely vehicle paths that are consistent with reported locations. Path inference requires a priori assumptions about link travel times; using unrealistic initial link travel times can bias the travel time estimation and subsequent identification of shortest paths. Thus, the combination of path inference and travel time estimation is a joint problem. This paper investigates the sensitivity of estimated travel times, and proposes a fixed point formulation of the simultaneous path inference and travel time estimation problem. The methodology is applied in a case study to estimate travel times from taxi FCD in Stockholm, Sweden. The results show that standard fixed point iterations converge quickly to a solution where input and output travel times are consistent. The solution is robust under different initial travel times assumptions and data sizes. Validation against actual path travel time measurements from the Google API and an instrumented vehicle deployed for this purpose shows that the fixed point algorithm improves shortest path finding. The results highlight the importance of the joint solution of the path inference and travel time estimation problem, in particular for accurate path finding and route optimization. 相似文献
2.
This paper investigates crowding effect on the path choice of metro passengers. We show people reroute not only to avoid the delay from crowding but also to evade crowding itself. More specifically, a logit model fits best when it uses the transit delay from crowding as well as the passenger load of a connection in addition to the conventional explanatory variables. Also, we demonstrate that crowding decreases the overall welfare of metro passengers. The model is tested on the real path choice data acquired by the recent algorithm by Hong et al. (2015) known to detect the real path choice from Smart Card data in more than 90% of the cases. 相似文献
3.
基于前轮转角约束自适应模型预测控制的路径跟踪研究 总被引:1,自引:0,他引:1
针对在车辆行驶中较小的前轮转角无法充分利用路面附着能力,较大的前轮转角使得车辆的行驶稳定性差的问题,文章提出了一种前轮转角约束自适应模型预测方法。首先建立车辆的动力学模型,然后通过计算得到轮胎纵向力,最终得到车辆的前轮转角。将车辆的状态量与前轮转角自适应约束条件输入给模型预测控制器,输出车辆的前轮转角,实现对参考路径的跟踪。在Carsim和MATLAB平台上联合仿真,仿真结果表明前轮转角约束自适应模型预测控制的车辆相比固定转角约束的车辆具有较好的跟踪能力和稳定性。 相似文献
4.
5.
统计能量法及其在提速客车噪声预测中的应用 总被引:3,自引:0,他引:3
为了预测提速客车内部噪声能量分布及噪声传递路径,用统计能量法对其进行了分析,讨论了统计能量法分析复杂振声系统的基本原理及稳态振声系统统计能量分析的基本方程.以唐山车辆厂提速客车为应用实例,获得了车内总的声功率在车底架、窗玻璃等主要传递路径上的能量分布,并给出了车窗双层玻璃不同厚度的高频响应以及车底架地板涂抹阻尼材料吸收低频声能的机理的治理措施。 相似文献
6.
7.
E. Frejinger M. Bierlaire M. Ben-Akiva 《Transportation Research Part B: Methodological》2009,43(10):984-994
This paper presents a new paradigm for choice set generation in the context of route choice model estimation. We assume that the choice sets contain all paths connecting each origin–destination pair. Although this is behaviorally questionable, we make this assumption in order to avoid bias in the econometric model. These sets are in general impossible to generate explicitly. Therefore, we propose an importance sampling approach to generate subsets of paths suitable for model estimation. Using only a subset of alternatives requires the path utilities to be corrected according to the sampling protocol in order to obtain unbiased parameter estimates. We derive such a sampling correction for the proposed algorithm.Estimating models based on samples of alternatives is straightforward for some types of models, in particular the multinomial logit (MNL) model. In order to apply MNL for route choice, the utilities should also be corrected to account for the correlation using, for instance, a path size (PS) formulation. We argue that the PS attribute should be computed based on the full choice set. Again, this is not feasible in general, and we propose a new version of the PS attribute derived from the sampling protocol, called Expanded PS.Numerical results based on synthetic data show that models including a sampling correction are remarkably better than the ones that do not. Moreover, the Expanded PS shows good results and outperforms models with the original PS formulation. 相似文献
8.
9.
Assessing the cost of transfer inconvenience in public transport systems: A case study of the London Underground 总被引:2,自引:0,他引:2
Few studies have adequately assessed the cost of transfers2 in public transport systems, or provided useful guidance on transfer improvements, such as where to invest (which facility), how to invest (which aspect), and how much to invest (quantitative justification of the investment). This paper proposes a new method based on path choice,3 taking into account both the operator’s service supply and the customers’ subjective perceptions to assess transfer cost and to identify ways to reduce it. This method evaluates different transfer components (e.g., transfer walking, waiting, and penalty) with distinct policy solutions and differentiates between transfer stations and movements.The method is applied to one of the largest and most complex public transport systems in the world, the London Underground (LUL), with a focus on 17 major transfer stations and 303 transfer movements. This study confirms that transfers pose a significant cost to LUL, and that cost is distributed unevenly across stations and across platforms at a station. Transfer stations are perceived very differently by passengers in terms of their overall cost and composition. The case study suggests that a better understanding of transfer behavior and improvements to the transfer experience could significantly benefit public transport systems. 相似文献
10.
本文针对复杂曲面加工中存在的刀具轨迹计算和干涉判断复杂的问题,将最小有向距离算法应用于复杂曲面的加工中。通过对曲面加工原理分析,将求刀触点的问题转化为数学规划问题。实验证明该方法有对曲面适应范围广,计算量小、计算速度快等特点,适用于复杂曲面的加工。 相似文献