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Closed-loop control of a snowplow applicator, based on direct measurement of the road surface condition, is a valuable technology for the optimisation of winter road maintenance costs and for the protection of the environment from the negative impacts of excessive usage of de-icing chemicals. To this end, a novel friction measurement wheel is designed to provide a continuous measurement of road friction coefficient, which is, in turn, utilised to control the applicator automatically on a snowplow. It is desired that the automated snowplow applicator deploy de-icing materials right from the beginning of any slippery surface detected by the friction wheel, meaning that no portion of the slippery road surface should be left untreated behind, as the snowplow travels over it at a reasonably high speed.

This paper describes the developed wheel-based measurement system, the friction estimation algorithm and the expected performance of the closed-loop applicator system. Conventional and zero velocity applicators are introduced and their hardware time delays are measured in addition to the time delay of the friction estimation algorithm. The overall performance of the closed-loop applicator control system is shown to be reliable at typical snowplowing speeds if the zero velocity applicator is used.  相似文献   

3.
This article identifies tyre modelling features that are fundamental to the accurate simulation of the shear forces in the contact patch of a steady-rolling, slipping and cambered racing tyre. The features investigated include contact patch shape, contact pressure distribution, carcass flexibility, rolling radius (RR) variations and friction coefficient. Using a previously described physical tyre model of modular nature, validated for static conditions, the influence of each feature on the shear forces generated is examined under different running conditions, including normal loads of 1500, 3000 and 4500 N, camber angles of 0° and?3°, and longitudinal slip ratios from 0 to?20%. Special attention is paid to heavy braking, in which context the aligning moment is of great interest in terms of its connection with the limit-handling feel. The results of the simulations reveal that true representations of the contact patch shape, carcass flexibility and lateral RR variation are essential for an accurate prediction of the distribution and the magnitude of the shear forces generated at the tread–road interface of the cambered tyre. Independent of the camber angle, the contact pressure distribution primarily influences the shear force distribution and the slip characteristics around the peak longitudinal force. At low brake-slip ratios, the friction coefficient affects the shear forces in terms of their distribution, while, at medium to high-slip ratios, the force magnitude is significantly affected. On the one hand, these findings help in the creation of efficient yet accurate tyre models. On the other hand, the research results allow improved understanding of how individual tyre components affect the generation of shear forces in the contact patch of a rolling and slipping tyre.  相似文献   

4.
In this first part of a two-part article, a previously described and validated finite-element model of a racing-car tyre is developed further to yield detailed information on carcass deflections and contact pressure and shear stress distributions for a steady rolling, slipping, and cambered tyre. Variations in running conditions simulated include loads of 1500, 3000 and 4500 N, camber angles of 0° and ?3°, and longitudinal slips from 0% to?20%. Special attention is paid to heavy braking, in which context the aligning moment is of great interest. Results generated are in broad agreement with limited experimental results from the literature and they provide considerable insight into how the tyre deforms and how the contact stresses are distributed as functions of the running conditions. Generally, each rib of the tyre behaves differently from the others, especially when the wheel is cambered. The results form a basis for the development of a simpler physical tyre model, the purpose of which is to retain accuracy over the full operating range while demanding much less computational resource. The physical tyre model is the topic of the second part of the article.  相似文献   

5.
The numerical wheel wear prediction in railway applications is of great importance for different aspects, such as the safety against vehicle instability and derailment, the planning of wheelset maintenance interventions and the design of an optimal wheel profile from the wear point of view. For these reasons, this paper presents a complete model aimed at the evaluation of the wheel wear and the wheel profile evolution by means of dynamic simulations, organised in two parts which interact with each other mutually: a vehicle's dynamic model and a model for the wear estimation. The first is a 3D multibody model of a railway vehicle implemented in SIMPACK?, a commercial software for the analysis of mechanical systems, where the wheel–rail interaction is entrusted to a C/C++user routine external to SIMPACK, in which the global contact model is implemented. In this regard, the research on the contact points between the wheel and the rail is based on an innovative algorithm developed by the authors in previous works, while normal and tangential forces in the contact patches are calculated according to Hertz's theory and Kalker's global theory, respectively. Due to the numerical efficiency of the global contact model, the multibody vehicle and the contact model interact directly online during the dynamic simulations.

The second is the wear model, written in the MATLAB® environment, mainly based on an experimental relationship between the frictional power developed at the wheel–rail interface and the amount of material removed by wear. Starting from a few outputs of the multibody simulations (position of contact points, contact forces and rigid creepages), it evaluates the local variables, such as the contact pressures and local creepages, using a local contact model (Kalker's FASTSIM algorithm). These data are then passed to another subsystem which evaluates, by means of the considered experimental relationship, both the material to be removed and its distribution along the wheel profile, obtaining the correspondent worn wheel geometry.

The wheel wear evolution is reproduced by dividing the overall chosen mileage to be simulated in discrete spatial steps: at each step, the dynamic simulations are performed by means of the 3D multibody model keeping the wheel profile constant, while the wheel geometry is updated through the wear model only at the end of the discrete step. Thus, the two parts of the whole model work alternately until the completion of the whole established mileage. Clearly, the choice of an appropriate step length is one of the most important aspects of the procedure and it directly affects the result accuracy and the required computational time to complete the analysis.

The whole model has been validated using experimental data relative to tests performed with the ALn 501 ‘Minuetto’ vehicle in service on the Aosta–Pre Saint Didier track; this work has been carried out thanks to a collaboration with Trenitalia S.p.A and Rete Ferroviaria Italiana, which have provided the necessary technical data and experimental results.  相似文献   

6.
多年冻土地区路基冻胀变形分析   总被引:19,自引:4,他引:19  
首先模拟气候因素变化过程,得到不同时期冻土路基温度场分布,温度场随时间的变化可以反映出冻结相变区的变化,然后考虑土体体积力和土体冻结相变产生的冻胀力,采用考虑拉破坏的热弹性力学方法,分析得到多年冻土地区路基变形分布和演变规律;在此基础上,对冻土路基纵向裂缝的成因进行研究,揭示出冻土路基纵向裂缝主要出现于路面中部及路面靠近路肩部位,这与实际情况是相符合的。进一步的分析表明:采用低冻胀性的土填筑路基,如采用碎石土填筑,对于降低冻土路基冻胀变形及防治纵向裂缝病害是有效的。  相似文献   

7.
新疆公路三级区划设计参数的研究   总被引:7,自引:1,他引:7  
在现行自然区划的基础上,从设计和施工的需要入手,提出了建立在新疆公路三级自然区划基础上的新疆公路设计参数:土基回弹模量E0和加州承载比CBR(California Bearing Ratio)。论述了设计参数资料收集的数据内容及应注意的问题,采用数理统计方法从收集的资料数据中确定不同土质在不同自然区的E0值、CBR值均值的上、下限,并对其进行了相关性分析。通过分析建立了新疆各三级自然区较精确的设计参数数值的推荐范围,并对取值作出详细说明,为新疆地区的公路设计提供了可靠依据。  相似文献   

8.
当哈尔滨市进行大规模的基础建设 ,“两轴四环十二射”路网格局已初具规模时 ,陡坡路段的使用状况却未引起有关部门的关注。本文从路网整体效率的发挥和行车安全等角度分析了陡坡路段的重要性及其对交通的影响 ,分析了陡坡路段路面破损的原因 ,并从建设与管理两个方面提出了改善陡坡路段行车条件的措施。  相似文献   

9.
沥青路面的热粘弹性温度应力分析   总被引:1,自引:0,他引:1  
基于沥青路面混合料的热粘弹属性,利用有限元对不同降温条件以及不同结构形式的沥青路面温度应力响应进行了分析,研究了降温速率、初始温度、降温幅度、面层厚度、基层模量和温缩系数对温度应力的影响。结果表明,当温度较高时,沥青路面的温度收缩应力的累积值非常小;初始温度与降温速度对沥青路面的温度应力影响显著;薄的沥青面层容易出现反射裂缝,厚的沥青面层则可能出现由沥青面层表面向基层裂缝发展的对应裂缝;沥青路面的基层模量不宜过大。  相似文献   

10.
软土地基高速公路扩建中新老路堤相互作用数值分析   总被引:9,自引:1,他引:9  
采用弹塑性有限元方法分析了老路边坡开挖和加宽部分路堤填筑对老路变形特性的影响。计算结果表明:原有路堤边坡削坡和台阶开挖将会使得老路中心的竖向沉降略有增加,坡脚侧向位移回缩,且不同开挖方式对原有路堤影响不同;加宽部分路堤的填筑将会使得老路中心上抬,路肩点发生较大附加沉降,引起老路路肩与路中心之间产生过大的附加差异沉降,明显加大路面横坡,极易导致对老路路堤、路面的拉裂,降低道路等级,必须采用合适的软基处理方案对加宽部分软基进行处理。另外,宽路堤的变形特性不同于窄路堤,其沉降呈中央小两边大的形式,并且最大沉降位置随路堤高度的增加向路堤中央移动,了解宽路堤变形的这一特性有助于其软基处理方案以及加固效果监测方案的优化。  相似文献   

11.
基于对流效应的寒区路堤块石层临界高度研究   总被引:1,自引:2,他引:1  
为了研究块石路堤降温效应与块石层高度之间的关系,基于多孔介质自然对流理论和热传导理论引入了表征寒区块石路堤自然对流降温效应的自然对流指数,利用热传导温度分布函数获得了路堤自然对流指数随块石层高度变化的近似公式。分析表明:自然对流指数最小值对应于路堤块石层的最小高度,而其最大值对应于路堤块石层的最大高度。另外介绍了一种利用自然对流指数近似公式估算路堤块石层临界高度的方法,并具体给出了算例,最后进行了数值验算。结果表明:通过自然对流指数确定的临界高度可为寒区工程的路堤设计提供参考。  相似文献   

12.
山西运煤专线水泥混凝土试验路结构分析   总被引:1,自引:1,他引:1  
针对山西省运煤专线行驶的车辆轴重大、轮压高和多轴化的特点,采用弹性地基上多层结构模型,对试验路段素水泥混凝土(PCP)路面结构组合的荷载应力、温度应力进行了仔细的计算分析,给出了钢筋混凝土(JRCP)、连续配筋混凝土(CRCP)路面的配筋率,进而对试验路不同路面结构组合的疲劳寿命进行预估.结合近期试验路段路况调查结果,对试验段不同路面结构组合形式的适应性进行评价分析.分析表明,(1)增加水泥混凝土面层厚度,是保证运煤专线在车辆轴重大、轮压高和多轴化作用下具有较高疲劳寿命的首要选择;(2)采用连续配筋混凝土结构组合,存在裂缝间距不能控制在规范要求的范围内;(3)采用双层钢筋网的钢筋混凝土路面结构组合较素混凝土、连续配筋混凝土结构组合更有优势.  相似文献   

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