基于功率谱密度的路面评价与特征参数提取

介绍了道路路面数据测量系统的构成和数据预处理方法。针对测量的海量道路路面数据,阐述了路面数据的功率谱密度分析与传统的功率谱分析的差异,解读了GB/T7031-2005中的倍频程滤波和路面分级方法,提出了基于拟合直线的斜率截距路面特征参数提取方法和基于功率谱密度曲线的路面分级百分比例特征参数提取方法。在介绍路面评价和特征参数提取方法的基础上,使用真实的路面测量数据作为例子,充分显示了这两种路面特征参数提取方法的效果。实例分析结果表明,使用这两种路面特征参数提取方法来评价和分析道路路面数据,计算过程快捷方便,处理效果简单明显,可在道路路面数据的特征参数提取及其它工程振动信号的统计分析中推广应用。     

典型路面的提取与合成方法研究

介绍了道路路面数据测量系统的构成和数据预处理方法。针对测量的道路路面数据,提取了可表征路面特点的特征参数,包括基本统计量、国际平整度指数和功率谱密度参数等。在此基础上,使用雷达图统计分析工具,提出了典型路段的提取与合成算法。并以北京地区真实的海量路面测量数据为例,进行了典型路面的提取与合成,得到了可反映和表征该地区路面特点的典型路面。最后总结了典型路面的提取与合成方法,展望了其应用前景。     

典型道路谱的生成方法研究

代表地区路面不平度总体状况的道路谱数据,在汽车设计研发中起着重要作用,但目前缺少获取典型道路谱的方法。为了解决这一问题,本文提出了一种典型道路谱生成方法,该方法包含典型路段选取和测量、道路谱计算和滤波、典型道路谱提取三个主要步骤。以北京地区真实路面测量数据为例,进行典型道路谱生成,得到了能够表征某类路面的典型谱。该方法工程意义明确,效果明显,在汽车工程和道路工程领域有较大应用价值。     

海量道路路面测量数据的若干预处理方法研究

回顾了道路路面数据的测量系统的构成和测试方法。针对海量的道路路面试验数据,将若干信号处理的预处理方法,包括粗大误差的甄别与剔除、信号趋势项的提取、分段试验数据的平滑过渡连接、路面数据随机性检验和车速异常时刻的处理等应用于海量道路路面数据的分析处理中,并进行了相应的改进。在分析这些预处理方法原理的基础上,使用实际采集的试验路面数据作为例子,充分显示了这些方法的处理效果。实例分析结果表明,这些信号预处理方法用来处理和修正道路路面试验数据,使用简单方便,处理效果明显,可在道路路面数据处理及其它工程振动信号预处理中推广应用。     

开孔结构内压传递方程的孔口特征参数识别

对开孔结构内压传递方程的孔口特征参数识别进行理论和实验研究。基于通用双参数内压传递方程,探讨了在正弦波激励下考虑非线性阻尼的孔口特征参数提取方法,并采用时程计算方法对参数提取的精度进行了详细分析,设计并制作了专用的实验装置用于孔口特征参数提取。研究结果表明,基于正弦波激励的孔口特征参数提取方法在共振峰附近的提取精度较为可靠,而发生共振反应是保证孔口参数提取精度的前提。     

不同拉伸速率下钢材损伤的声发射监测评价

钢材已成为生产的基本材料,被广泛应用于各行业,目前还没有对其进行损伤动态监测的有效方法。采用声发射技术对钢材Q235在不同的拉伸速率下进行损伤动态监测试验研究,首先通过试验获取了不同拉伸速率时材料的弹性、屈服、强化、颈缩和断裂各个力学行为阶段声发射信号并提取各个特征参数;然后通过各个特征参数累积量历程图归一化曲线对钢材拉伸损伤过程进行评价,发现特征参数累积量历程图归一化曲线可以明显反映出钢材拉伸整体演变过程及各个力学行为阶段特征,并且随着拉伸速率的减小,在屈服阶段的结束端点出现更为明显的突增量,可作为表征屈服阶段和强化阶段的重要转折点。结合拉伸力学,对各个力学行为阶段声发射信号的产生机制和特征进行总结,可为钢材后期声发射信号源的产生机制以及后期损伤定量、寿命预测的研究提供参考了依据。     

金属拉深件拉深过程微裂纹AE信号特征参数的优化及状态识别

本文通过对拉深件成型状态的声发射测试,进行了拉深过程AE特征参数信号的提取。对采集到的信号进行局域波分解后提取各IMF(Intrinsic Mode Function)的能量值作为初始特征参数,应用遗传算法对初始特征参数进行优化,生成最优特征参数。采用简单的马氏距离方法,将正常状态和微裂纹状态两种质量状态下的实验数据进行计算,比较两种状态下马氏距离的大小,取其中最小判别距离对应的状态为测试样本的状态类型。研究结果说明了该方法可以有效地识别出拉深件的微裂纹AE信号,从而判断出拉深件的初始裂纹状态,实现AE信号特征参数的优化及对金属拉深件成型质量状态的识别。     

摩擦振动时频图像特征提取

针对摩擦振动特征难以有效提取的问题,提出利用连续小波变换（ＣＷＴ）时频谱图像和图像处理技术提取摩擦振动特征参数的方法。运用ＣＷＴ变换绘制６Ｓ５０ＭＣ船用柴油机缸套－活塞环试样摩擦振动信号的时频谱图,再用图像分割技术提取振动特征体及相应的特征参数,探讨特征参数与不同润滑剂润滑条件下缸套－活塞环摩擦振动特性的内在联系。结果表明,随着摩擦磨损过程的进行,摩擦振动信号特征参数出现规律性变化;不同润滑工况下的特征参数呈现出明显的差异,反映了摩擦磨损的状态。振动特征体特征参数能定量刻画摩擦振动信号的特征。     

基于几何特征的不平整路面三维建模与分析研究

在对比利时路关键几何特征、特征的分布特点及其约束条件进行分析的基础上,提出了基于几何特征的参数化路面三维建模方法。通过比利时路三维理论模型与生成的三维随机路面融合,得到真实准确的比利时路三维模型;在建立标准化车辆振动模型的基础上,以IRI指数和车身振动加速度均方根值(RMS)作为评价指标,分析了比利时路的关键几何参数对车辆振动的影响。通过实测道路数据与所建立模型对比分析,验证模型的准确性;提出的道路三维建模方法可以扩展至卵石路、鱼鳞坑路、波纹路、搓板路等几乎所有不平整强化试验路面,为全面构建车辆虚拟试验场提供了一种参数可调、真实准确的道路三维建模途径。     

基于小波包变换和奇异值分解的柴油机振动信号特征提取研究

为通过振动信号识别柴油机的工作状态,提出利用小波包变换和奇异值分解提取振动信号特征的新方法。给出了小波包变换算法及奇异值分解算法,依据矩阵奇异值特征向量,定义了振动信号特征参数,并探讨了特征参数与柴油机运行状态之间的内在联系。结果表明：特征参数能够敏感地反映柴油机工作性能的变化。随着柴油机工作性能的恶化,振动强度的增加,特征参数变大。特征参数可作为柴油机状态监测和故障诊断的特征量。     

道路路面的剖面曲线测量研究与实践

回顾了近年来道路路面测量各种方法的研究现状,介绍了自主开发的高精度道路路面测量系统的测量原理和试验方法。在此基础上针对道路路面的真实剖面曲线测量方法进行了探讨和分析,并通过一些对比分析试验对该方法的测量误差进行了讨论,得到了较好的分析试验结果。最后针对道路路面的剖面曲线测量方法进行了总结,对该方法的应用范围和优缺点进行了评价。     

Comparison of fourier-transform and data-dependent system profilometry by use of interferometric regeneration

Fourier-transform profilometry (FTP) and data-dependent system profilometry (DDSP) are the two major phase-extraction methods that use a single interferogram. The difficulty in verifying surface profiles obtained by these methods is that the exact spot on an actual surface cannot be measured with two different instruments. An interferogram regeneration procedure is developed to solve this problem. The surface profile is then extracted from the regenerated interferogram by both FTP and DDSP. Comparisons of the actual surface profile with the extracted surface profiles show that both methods perform equally well in measuring the root mean square and the center line average, but only DDSP is able to reproduce the detailed surface profile of the reference surface.     

3D road modeling via the integration of large-scale topomaps and airborne LIDAR data

Abstract

Modern road systems have become complex networks with multiple layers, making three- dimensional (3D) road modeling an important task in the geoinformatic realm. Although traditional topographic maps contain explicit planimetric networks, they often lack sufficient elevation information to describe the vertical alignments in multi-layer road systems. In this investigation, we combine data from large-scale topographic maps and airborne light detection and ranging (LIDAR) data to reconstruct 3D road models. The proposed scheme includes two steps: planimetric networking and surface modeling. In the first part, road centerlines are determined then linked up and their topologies organized using the polylines extracted from large-scale topographic maps. In the second part, a filter is utilized for the extraction of road surface points from airborne LIDAR data. The three dimensional alignment of the profiles and cross-sections is then computed. Furthermore, to improve the realism of the road models, surfaces are constrained by continuities of slope and slope difference. There are three types of data included in the test data set: single-layer, multi-layer, and interchanges between road systems. In addition to the elevation accuracy, surface continuity, slopes, and slope differences of the modeled roads are also analyzed.     

Mapping road surface features using single-camera images acquired by a mobile mapping system

Mapping road surface features, such as manholes, traffic markings, and cracks, is an essential task for transportation facility management. Although, these features can be rapidly surveyed using the latest mobile mapping techniques, a sophisticated sensor system with a complicated post-processing procedure is usually required. In this study, an efficient framework for modeling road surface features is proposed using a single camera system installed on a moving platform. First, the road surface images along a route of interest are acquired and potential objects are identified based on their shapes and recorded spectra in the images. Then, the contour pixels of the identified objects are extracted by the Canny edge detection technique. Finally, the 3D coordinates of the detected features in object space are obtained by integrating the profile-image technique and the instantaneous exterior orientation parameters of the platform. Based on the numerical results from a case study, it has been demonstrated that a fully automatic and reliable extraction of road surface features can be easily achieved by implementing the proposed approach. Consequently, the modeling of road surface features, which essentially contributes to the management of transportation facilities, can be executed in a cost-efficient manner.     

断口分形研究与应用

采用经典的Ｍａｎｄｅｌｂｒｏｔ分形模型、Ｕｎｄｅｒｗｏｏｄ修正分形模型和分维谱模型对三种球墨铸铁断口的分形特性进行了研究，并应用于铸态铁拉伸断口的断 断裂机制分析。     

White noise excitation of road vehicle structures

Heave and pitch motions of road vehicle structures affect the comfort and the safety of passengers. Excitation of these vertical vibrations is due to road surface roughness. Road vehicle structures are modelled as mechanical systems characterized by their inertia, damping and stiffness, and represented as state equations. This paper deals with the influence of random road profiles on the vertical dynamics of road vehicles characterized by stochastic processes. Switching from road profile displacement to road profile velocity results in white noise excitation facilitating mathematical analysis. Some fundamentals of power spectral density analysis and covariance analysis are reviewed. A quarter car model is used to show the advantages of the covariance analysis resulting immediately in standard variations characterizing the vehicle’s performance. A list of symbols is given at the end of the paper This paper is dedicated to Prof R N Iyengar of the Indian Institute of Science on the occasion of his formal retirement.