Long-term static testing of an FRP prototype highway structure

In recent years it has become apparent that the labour and maintenance costs of highway structures fabricated from conventional constructional materials (i.e. steel and concrete) are rising, and therefore the whole life cost of these structures is being significantly affected. Highway structures manufactured from advanced composite materials provide a viable solution to reduce substantially both the labour and the maintenance costs, whilst providing structures that behave in accordance with the present British code of practice for highway structures.

The principle objectives of the investigations were to undertake experimentally and to verify, where applicable, numerically the suitability of advanced fibre-reinforced polymer (FRP) composite materials manufactured in the form of box beams for use as highway structures. It was also important to research into any unique behaviour exhibited by the FRP structures while under test and to develop relevant theoretical models and formulae to characterize completely this behaviour.

The composite box beam showed no signs of global deterioration and generally behaved as predicted; the short term stiffness of the beam measured at specific times during the test did not decrease to any extent. There was some local flexural cracking in the connectors at the position of the applied loads, but this can be eliminated by design. The creep and deflections of the beam at the end of the test were well within acceptable limits.     

Prediction of the yarn trajectories on complex braided preforms

Braiding can be used to manufacture preforms for resin transfer moulding (RTM). With braiding, many yarns are used, non-geodesic yarn paths are possible, and the interlaced structure of braids provides typical mechanical properties such as high impact strength. Previously, several models were developed to predict the fibre angles on simple, stationary braided preforms, but not for complex, non-axisymmetric preforms. This paper presents a fast and efficient model to predict the fibre angles on complex biaxially braided preforms. The model is verified with experiments on two mandrels and the experimental and numerical results show good agreement.     

Impact of age and cognitive demand on lane choice and changing under actual highway conditions

Previous research suggests that drivers change lanes less frequently during periods of heightened cognitive load. However, lane changing behavior of different age groups under varying levels of cognitive demand is not well understood. The majority of studies which have evaluated lane changing behavior under cognitive workload have been conducted in driving simulators. Consequently, it is unclear if the patterns observed in these simulation studies carry over to actual driving. This paper evaluates data from an on-road study to determine the effects of age and cognitive demand on lane choice and lane changing behavior. Three age groups (20–29, 40–49, and 60–69) were monitored in an instrumented vehicle. The 40's age group had 147% higher odds of exhibiting a lane change than the 60's group. In addition, drivers in their 60's were less likely to drive on the leftmost lane compared to drivers in their 20's and 40's. These results could be interpreted as evidence that older adults adopt a more conservative driving style as reflected in being less likely to choose the leftmost lane than the younger groups and less likely to change lanes than drivers in their 40's. Regardless of demand level, cognitive workload reduced the frequency of lane changes for all age groups. This suggests that in general drivers of all ages attempt to regulate their behavior in a risk reducing direction when under added cognitive demand. The extent to which such self-regulation fully compensates for the impact of added cognitive demand remains an open question.     

基于语义分割的实时车道线检测方法

车道线识别是自动驾驶环境感知的一项重要任务。近年来,基于卷积神经网络的深度学习方法在目标检测和场景分割中取得了很好的效果。本文借鉴语义分割的思想,设计了一个基于编码解码结构的轻量级车道线分割网络。针对卷积神经网络计算量大的问题,引入深度可分离卷积来替代普通卷积以减少卷积运算量。此外,提出了一种更高效的卷积结构LaneConv和LaneDeconv来进一步提高计算效率。为了获取更好的车道线特征表示能力,在编码阶段本文引入了一种将空间注意力和通道注意力串联的双注意力机制模块(CBAM)来提高车道线分割精度。在Tusimple车道线数据集上进行了大量实验,结果表明,本文方法能够显著提升车道线的分割速度,且在各种条件下都具有良好的分割效果和鲁棒性。与现有的车道线分割模型相比,本文方法在分割精度方面相似甚至更优,而在速度方面则有明显提升。

     

A probabilistic model for discretionary lane change proposals in highway driving situations

This contribution presents a novel probabilistic approach for the generation of discretionary lane change proposals with a focus on highway driving situations. The developed model is based on the quantification of the utility of driving lanes. It generates a lane change proposal if the current driving lane is unsatisfactory in the sense that the desired velocity of the automated vehicle is undershot because of a slow preceding vehicle. A driving simulator study was conducted to create a dataset for the optimization of the model parameters. The optimization goal is to accurately match the timings of the lane change intentions of all participants. Finally, the applicability of the model is shown on real data from a test vehicle.

     

Effects of changes in travel patterns on highway fatalities

This paper estimates the number of deaths that may have been avoided in 1995 because of changes in selected travel patterns during the period from 1969 to 1995 in the US. Four travel patterns are considered, including distributions of travel between urban and rural areas, between interstates and other roadways, between night and day time hours, and between female and male drivers. At the 1995 mobility level, changes in the selected travel patterns during the period from 1969 to 1995 may have avoided up to 9970 deaths in 1995 alone. These deaths avoided represent over 12% of the total number of deaths avoided in 1995 as a result of overall improvements in highway safety during the same period in this country.     

Reflektas: lane departure prevention system based on behavioural control

As a great portion of fatal accidents is caused by road departures, numerous systems for lateral control have been developed. These systems possess different functionalities, like warning the driver if he tends to depart from the lane or adding a steering torque to reduce the necessity for small steering corrections. To overcome some disadvantages of the classical systems and to develop a system for emergency situations, the knowledge of behavioural principles was utilised. A system based on reflexes has the potential of eliciting reactions reliably and quickly. In a simulator study, the principle was examined and different adjustments of the stimulus used to elicit target behaviour were tested. Subjective and objective data were collected. Results show that the participants trusted the system and perceived it as a valuable contribution to traffic safety. Objective data, like steering angle and measures of lateral position, were analysed and three different types of elicited reactions could be identified. Reaction time, reaction strength and a number of other measures were calculated for each type of reaction. The results confirmed that the system elicits reflexive reactions with very short delays, thus showing its potential for avoiding severe accidents.     

基于机器视觉的车道线在线识别系统设计

针对目前车道线识别系统因处理对象为离线图像或视频文件而难以实现车道线在线识别的问题,大多数车道线识别算法为了减少图像处理运行量,通常选取固定的兴趣区域（region of interest,ROI）进行处理,导致难以适应环境的动态变化且存在不同程度的识别误差。为此,提出了一种基于机器视觉的不设定兴趣区域的车道线在线识别系统。首先,利用VBAI（Vision Builder for Automation Inspection）平台对实时采集的彩色道路图像进行预处理,完成彩色图像的灰度化、滤波及二值化处理。然后,建立图像坐标系,并构建多条向外发散的灰度值采集线,灰度值采集线与车道线相交处的灰度值会发生较大改变,当某点的灰度值高于设定的灰度阈值时,记该点为边缘突变点。接着,借助直线拟合算法对所有车道边缘突变点进行拟合以完成车道线识别,并求解两侧内车道线的远方消失交点坐标和车辆行驶偏离车道中心线的相对航偏角,当相对航偏角超过不同等级的安全阈值时,系统人机交互界面的提示框呈现不同的颜色以进行提醒或预警。最后,借助LabVIEW进行API（application programming interface,应用程序接口）脚本调用,实现图像处理程序的连续运行与车道线在线识别。试验结果表明,所提出的车道线在线识别系统的识别准确率达98.41%以上,相对航偏角的测量误差小于0.056°,图像处理速度达42帧/s以上,兼具识别的准确性与实时性。综上可知,基于机器视觉的车道线在线识别系统可有效识别出不同环境路面的车道线,并实现行驶偏离预警,可将其应用于基于自动驾驶技术的车道保持辅助（lane keeping assist,LKA）系统。     

基于虚拟样机技术的万吨压机锻造操作机的运动学仿真分析

 万吨压机锻造操作机是重要的重载操作设备.锻造操作机钳头预期运动轨迹的精确实现,是实现锻造操作机基本功能的基础.基于虚拟样机技术,在ADAMS软件中建立了锻造操作机整机系统的虚拟样机,对操作机进行运动学仿真,得出钳头运动情况曲线,并将运动曲线与锻造操作机的设计参数进行比较,分析确定了操作机的运动性能良好,为设计操作机的详细结构提供了理论及数据依据.     

Creep trajectories for beech during moisture changes under load

Tensile creep experiments during concurrently changing humidities have been performed on Beech. There appears to be a threshold compliance level below which any change of moisture content, whether sorption or desorption, causes an increase in creep. Above this compliance level the creep appears to follow creep trajectories which form a shallow trough shape, for either humidification or dehumidification, when plotted with compliance as ordinate and moisture content as abscissa. The level of the threshold appears to vary with the instantaneous stiffness level of the material, measured at uniform moisture content. The mechano-sorptive creep below the threshold compliance could be explained in terms of the stress bias during hydrogen-bond breaking and remaking.     

High reliability outdoor sonar prototype based on efficient signal coding

Many mobile robots and autonomous vehicles designed for outdoor operation have incorporated ultrasonic sensors in their navigation systems, whose function is mainly to avoid possible collisions with very close obstacles. The use of these systems in more precise tasks requires signal encoding and the incorporation of pulse compression techniques that have already been used with success in the design of high-performance indoor sonars. However, the transmission of ultrasonic encoded signals outdoors entails a new challenge because of the effects of atmospheric turbulence. This phenomenon causes random fluctuations in the phase and amplitude of traveling acoustic waves, a fact that can make the encoded signal completely unrecognizable by its matched receiver. Atmospheric turbulence is investigated in this work, with the aim of determining the conditions under which it is possible to assure the reliable outdoor operation of an ultrasonic pulse compression system. As a result of this analysis, a novel sonar prototype based on complementary sequences coding is developed and experimentally tested. This encoding scheme provides the system with very useful additional features, namely, high robustness to noise, multi-mode operation capability (simultaneous emissions with minimum cross talk interference), and the possibility of applying an efficient detection algorithm that notably decreases the hardware resource requirements.     

基于虚拟样机技术的电梯动态设计与优化

为优化电梯动力学参数以提高电梯的乘坐舒适性,论文运用SolidWorks和ADAMS联合建立电梯的虚拟样机模型,给定约束和驱动,对虚拟样机进行动态仿真和分析.通过对电梯振动信号频域分析和多体动力学系统固有频率分析后,对电梯动力学参数进行优化.仿真结果表明,优化后电梯各项动态特性指标较优化前均有很大的改善,为改进电梯性能提供了设计依据.     

High-speed multiresolution scanning probe microscopy based on Lissajous scan trajectories

A novel scan trajectory for high-speed scanning probe microscopy is presented in which the probe follows a two-dimensional Lissajous pattern. The Lissajous pattern is generated by actuating the scanner with two single-tone harmonic waveforms of constant frequency and amplitude. Owing to the extremely narrow frequency spectrum, high imaging speeds can be achieved without exciting the unwanted resonant modes of the scanner and without increasing the sensitivity of the feedback loop to the measurement noise. The trajectory also enables rapid multiresolution imaging, providing a preview of the scanned area in a fraction of the overall scan time. We present a procedure for tuning the spatial and the temporal resolution of Lissajous trajectories and show experimental results obtained on a custom-built atomic force microscope (AFM). Real-time AFM imaging with a frame rate of 1 frame s?1 is demonstrated.     

CSCW技术中的公路物流系统研究

介绍了基于CSCW(计算机支持的协同工作)架构的公路物流系统的总体技术方案,通过将软件即服务(SaaS)技术、WebGIS技术等的融合,实现了CSCW对不同租户异质流程和异质数据支持的公路物流系统.实际应用表明,该系统对物流企业降低成本,提升运作效率,增强企业综合竞争力有着重要作用.     

基于多目标的IHI摆式飞剪虚拟样机优化

为解决多目标IHI摆式飞剪结构参数的优化,依据机构的基本参数,在ADAMS动力学分析软件中建立IHI摆式飞剪机构的数字化虚拟样机,仿真得到了上、下剪刃的动力学变化规律及其超前滞后特性.针对原设计中速度超前和滞后的问题,结合IHI摆式飞剪的组成原理建立了虚拟样机的多目标优化函数和约束条件.利用INSIGHT模块对数字化虚拟样机进行了优化分析.优化后的结构在一定程度上改善了原设计中的超前和滞后问题,更利于剪切和满足工艺需求.基于多目标的虚拟样机的优化分析,对于IHI摆式飞剪的结构参数设计及后期改造具有实际的指导意义.     

Design and testing of an energy absorber prototype based on aluminum foams

The current paper describes the methodology which has been used to design, fabricate and test an energy absorber system based on aluminum foams. The first step in the design process was devoted to define the requirements of the applications, important parameters such as the impact speed, impact force and the energy were defined. In a second part, a collection of aluminum foams were produced using the powder metallurgical route (PM) studying the mechanical properties of these materials. This process led us to define the characteristics of the aluminum foam to insert in the prototype, namely density and geometry. Finally, the energy absorber system was built, testing the whole system. The system worked properly, showing the excellent ability of aluminum foams in applications in which it is necessary to absorb the energy of an impact.     

基于虚拟样机技术的下肢假肢结构设计与仿真

下肢假肢动力学问题是智能仿生人工腿(intelligent bionic artificial limb prosthesis)研究领域中的重要内容．针对智能仿生人工腿,设计下肢假肢基本结构,运用Pro/E建立下肢假肢膝踝足关节模型,进行非线性动力学分析,并考虑了关节间的摩擦问题．最后,通过ADAMS虚拟样机技术,对人体行走步态进行仿真模拟控制,为下肢假肢、步行机器人研究提供了理论基础．     

Shape optimization of filament wound articulated pressure vessels based on non-geodesic trajectories

The most important issue for the design of articulated pressure structures reflects on the determination of the optimal meridian profile. In this paper, the optimal design for determining non-geodesics-based meridian profiles is outlined, subjected to geometrical limitations, stability-ensuring winding conditions and the Tsai–Wu failure criterion. The stress field is modeled using classical lamination theory, and the non-geodesic trajectories are employed to enlarge the design space and improve the structural performance. The searched optimal meridian profile is here approximated by cubic splines, which are based on equidistant knots. The objective is to maximize the performance factor using nonlinear optimization techniques. Two design problems are solved: firstly the optimal meridian profile determined using the present method is compared with the geodesic-isotensoid under the given opening radius. Secondly, the different optimal profiles with various slippage coefficients are obtained to demonstrate the effect non-geodesic trajectories have on the geometry and performance of articulated vessels. Results indicate that the articulated structure designed using the present method shows better performance, mainly triggered by increased internal volume as compared to that of the geodesic–isotensoid. Results also show that the structural performance of the articulated pressure vessel can further be improved with increasing slippage coefficients.     

基于虚拟样机技术的飞机起落架着陆载荷分析

起落架是飞机重要的承载机构,其在飞机的起飞、降落和着陆过程中担负着十分重要的作用。起落架着陆载荷是指在飞机着陆瞬间起落架所承受的地面载荷,根据位置的不同可分为轮胎接地点载荷、轮轴点载荷和交点载荷。飞机设计重量（包括空机重量、商载和燃油重量）的分布变化会对起落架着陆载荷产生影响。以典型民用飞机的起落架为研究对象,基于虚拟样机技术对起落架模型进行着陆分析。首先利用HyperMesh、MSC.Nastran软件对飞机起落架模型进行前处理和简化,然后根据中国民用航空规章运输类飞机适航标准相关条目要求,在MSC.ADAMS软件中设置相应的工况参数并进行起落架着陆动力学仿真分析,研究不同燃油密度下飞机的重量和重心变化对起落架轮轴点着陆载荷的影响。通过对比仿真结果可以发现：飞机的重量和重心变化对起落架轮轴点着陆载荷产生了明显的影响,而燃油密度变化对起落架轮轴点着陆载荷的影响较弱。研究结果可为今后有针对性地开展起落架着陆载荷计算提供参考和指导。     

大中口径舰炮敏捷供弹系统虚拟样机仿真研究

提出了一套完整的大中口径舰炮敏捷供弹系统。应用三雏实体建模软件PRO／E完成了整个供弹系统各个子系统的模型设计及建立；进行了装配检查，排除了零部件之间的干涉，完善了零部件设计；再利用PRO／E和ADAMS相结合，建立供弹系统各部分的驱动系统，并与实体模型结舍，对此系统进行机构的运动学、动力学和驱动系统仿真，对设计的可行性和合理性进行深入研究．通过以上研究，建立了一个完整的大中口径舰炮敏捷供弹系统虚拟样机，为供弹系统的进一步深入研究以实际生产提供了坚实的基础，同时给军械设计提供了一条高效率、低成本的设计方法．