桥梁健康监测中损伤特征提取的小波包方法

针对桥梁健康监测中结构损伤识别的特点,从模式识别的角度提出和分析了损伤特征提取问题.阐述了基于小波包分析的两种节点能量特征提取的方法.为了研究小波包系数节点能量和小波包信号成分节点能量对损伤信息进行特征提取的差异,通过对随机荷载激励下的连续梁进行数值模拟,得到了结构未损和损伤状态下的加速度时程信号.应用小波包变换,对不同结构状态下的加速度信号分别提取了两种小波包节点能量特征,并对它们作为结构损伤特征指标的敏感性进行了比较.认为两种特征指标的敏感性相差很小,而小波包系数节点能量特征指标的计算效率更高,更适合桥梁健康监测中损伤特征提取的要求.     

基于小波包能量变化率的钢桁架损伤识别研究

提出了一种基于小波包能量变化率的钢桁架结构损伤识别方法.运用Ansys软件对钢桁架结构进行数值模拟,得到结构各节点的加速度响应数据;利用Matlab对加速度响应数据进行小波包分析,然后通过小波包能量变化率指标识别损伤.主要研究了不同损伤位置、不同损伤程度、以及噪声对损伤识别的影响.数值模拟结果表明,小波包能量变化率指标能准确有效地识别损伤,该方法具有较好的鲁棒性.     

结构损伤识别的小波熵指标研究

利用小波变换时-频局部化和信息熵反映信源平均不确定性的特性,将小波分析和信息熵结合起来,提取小波能谱熵、小波时间熵和相对小波熵等结构损伤指标,并通过数值模拟和工字钢梁的试验数据对各损伤指标进行了分析检验.识别结果表明:基于小波熵的指标是一个对结构局部损伤敏感的、比较好的损伤指标.     

基于小波分析的大跨度桥梁动态监测数据处理

将GPS实时动态监测技术应用于大跨度桥梁监测是保障桥梁安全的重要手段,受到多种复杂因素的影响,如何提取大跨度桥梁的动态特性是应用该技术的关键。将小波分析应用于GPS桥梁动态监测数据处理,针对影响小波分析效果的小波基函数、小波分解尺度、阈值确定准则等3种因素进行对比实验,以均方差、信噪比和平滑度等3项评价指标进行量化分析,完成GPS桥梁动态特性的提取,获得有益的结论。     

基于小波变换的桥梁健康监测多尺度分析

针对桥梁结构健康监测具有实时性和数据量大的特点,提出了一种应用两个小波分别对实时测试数据进行分解和重构表达信号特征的方法,并定义了一个损伤指示系数,可按给定阈值在实时测试数据中搜寻损伤信息,确定损伤时刻,实现安全预警的目的.以一个发生损伤的两跨连续梁为例,对结构损伤进行了数值模拟,分析了在不同损伤位置及不同损伤率的情况下,损伤指示的敏感性.该实例表明对于梁中单元出现6%以上的刚度损伤有较好的损伤指示能力;由于多尺度分析方法具有较高的计算效率,能够在桥梁健康监测系统中在线完成损伤预警.     

基于小波包分解的数据融合损伤识别方法

目的为了充分利用来自多传感器的冗余、带噪声数据，提高结构损伤识别的精度．方法利用小波包良好的时一频特性，首先用小波包分解对结构响应进行处理．提取信号的不同特征参数，然后利用不同的特征向量对结构分别进行损伤识别，最后应用融合技术对不同的识别结果进行融合处理．并用一个七层钢结构框架的多损伤识别验证了该方法的有效性．结果结果表明，该方法能够极大地提高了结构损伤识别精度．结论运用小波包分析提取信号的特征参数与数据融合技术进行损伤识别．并使二者有机的结合是结构健康监测与检测的有效途径与发展趋势．     

基于小波包分析的空间杆系结构损伤诊断

针对结构损伤诊断的需要,采用小波包分析方法提取了结构损伤的特征信号。首先通过小波包分析将振动信号分解到各个频带,然后以各频带能量作为识别故障的特征向量进行损伤识别。数值算例表明,小波包分析具有较强的抗噪声干扰能力,能够有效地识别结构的损伤。     

空间单层网壳结构损伤杆件位置识别试验

为解决空间钢结构震后常发生杆件损伤的位置识别问题,设计一个单层网壳结构试验模型,切断单个杆件模拟实际结构的杆件损伤,对该损伤杆件进行位置识别研究.首先,根据空间钢结构自由度多,模态密集等特点,基于小波包能量分析法处理频率密集信号的优势,应用单层钢网壳结构损伤前后两个监测阶段的加速度响应数据,建立抗噪性能和灵敏性较好的损伤杆件位置识别指标向量.再应用有限元软件ANSYS建立17组不同位置杆件损伤的数值分析模型,分别获得17组有限元模型损伤前后的加速度响应数据,通过小波包分析处理后将其损伤指标向量作为损伤识别样本库,再将具有单个杆件损伤试验结构的加速度响应数据处理后得到的损伤识别指标向量与损伤样本库中各杆件损伤位置的指标向量进行聚类分析,识别出实际结构杆件有可能的损伤位置.该方法能够快速识别出实际结构中损伤杆件可能损伤的区域位置,试验结果也验证了方法的可行性和有效性,为后续工程应用研究提供了理论和试验支持.     

具有预警功能的顾客满意度数学模型研究

根据预警系统的设计理论，构建了顾客满意度预警系统，其内容包括了顾客满意度预警指标系统，顾客满意度预警信号系统，确定顾客满意度预警界限。并以东风雪铁龙轿车的顾客满意度预警为实证分析，对该品牌轿车的顾客满意度预警情况进行计算、分析，针对雪铁龙轿车的不足之处提出了相关的预警措施。这对改善公司营销系统工作状态有一定的作用。     

基于子频带性能分析的小波包树选择性研究

该文基于小波包调制系统在不同信道中各子带的传输性能的研究,从信道对小波包调制系统传输性能影响的角度,利用对满树调制结构的剪枝合并,探讨与频率选择性信道相匹配的小波包调制结构。仿真表明所选择的小波包树结构,不仅保证了小波包调制系统的传输性能,具有更简单的结构模式,而且具备数据多速率传输的特性。     

Environmental variability study on the measured responses of Runyang Cablestayed Bridge using wavelet packet analysis

The structural damage alarming method based on wavelet packet energy spectrum (WPES) for long-span cable-stayed bridges is presented through combination of ambient vibration test and wavelet packet analysis. The environmental variability in the measured WPES and damage alarming indices ERVD of the Runyang Cable-stayed Bridge are discussed in detail using the wavelet packet analysis of the measured acceleration responses of the bridge under daily environmental conditions. The analysis results reveal that the actual environmental conditions including traffic loadings, environmental temperature and typhoon loadings have remarkable correlations with the measured WPES. The changes of environmental temperature have a long-term trend influence on the WPES, while the influences of traffic and typhoon loadings on the measured WPES of the bridge present instantaneous changes because of the nonstationary properties of the loadings. The analysis results of the measured responses further reveal that the damage alarming indices ERVD can sensitively reflect the influences of environmental temperature and typhoon loadings on the dynamic properties of Runyang Cable-stayed Bridge. Therefore, the proposed structural damage alarming indices ERVD under ambient vibrations are suitable for real-time damage alarming for long-span cable-stayed bridges. Supported by the National Hi-Tech Research and Development Program of China (Grant No. 2006AA04Z416) and the National Natural Science Foundation of China (Grant No. 50538020)     

Research on seasonal correlation of wavelet packet energy spectrum and temperature of Runyang Suspension Bridge

In order to establish an environmental-condition-normalized structural damage alarming method, the seasonal correlation analysis of wavelet packet energy spectrum (WPES) and temperature of Runyang Suspension Bridge is performed by means of the 236-day health monitoring data. The analysis results reveal that the measured WPES has remarkable seasonal correlation with the environmental temperature. The seasonal change of environmental temperature accounts for the variation of the damage alarming parameter I _p of the dominant frequency bands with an averaged variance of 200%. The statistical modeling technique using a 6th-order polynomial is adopted to formulate the correlation between the WPES and temperature, on the basis of which the abnormal changes of measured damage alarming parameter I _p are detected using the mean value control chart. It is found that the proposed method can effectively eliminate temperature complications from the time series of WPES and exhibit good capability for detecting the damage-induced 10% variances of the damage alarming parameter I _p . And the proposed WPES-based method is superior the modal frequency and hence is more suitable for online real-time damage alarming for long-span bridges. Supported by the National Natural Science Foundation of China (Grant Nos. 50725828, 50808041) and the Natural Science Foundation of Jiangsu Province (Grant No. BK2008312)     

Features of energy distribution for blast vibration signals based on wavelet packet decomposition

Blast vibration analysis constitutes the foundation for studying the control of blasting vibration damage and provides the precondition of controlling blasting vibration. Based on the characteristics of short-time nonstationary random signal, the laws of energy distribution are investigated for blasting vibration signals in different blasting conditions by means of the wavelet packet analysis technique. The characteristics of wavelet transform and wavelet packet analysis are introduced. Then, blasting vibration signals of different blasting conditions are analysed by the wavelet packet analysis technique using MATLAB; energy distribution for different frequency bands is obtained. It is concluded that the energy distribution of blasting vibration signals varies with maximum decking charge,millisecond delay time and distances between explosion and the measuring point. The results show that the wavelet packet analysis method is an effective means for studying blasting seismic effect in its entirety, especially for constituting velocity-frequency criteria.     

基于小波包分析的结构损伤定位方法

提出了基于小波包节点能量（WPCE）相对变化量的结构损伤定位方法，采用其斜率向量和曲率向量2个指标作为损伤定位的依据，从而做到对于结构损伤的无模型定位，最后通过数值算例验证了该方法的可行性。     

基于PCA-BP的高等教育过度预警模型及其应用研究

通过专家访谈和文献查阅的方法,初步建立高等教育过度预警指标集,并运用主成分分析法(PCA)对指标进行逐步筛选,确立高等教育过度预警指标体系,然后,将PCA指标逐步筛选法和BP神经网络相结合,构建PCA-BP预警模型,对我国2002年高等教育发展进行评价,从而得出其发展状况在正常至轻微过度之间的结论。     

Features of energy distribution for blast vibration signals based on wavelet packet decomposition

Blast vibration analysis constitutes the foundation for studying the control of blasting vibration damage and provides the precondition of controlling blasting vibration. Based on the characteristics of short-time non-stationary random signal, the laws of energy distribution are investigated for blasting vibration signals in different blasting conditions by means of the wavelet packet analysis technique. The characteristics of wavelet transform and wavelet packet analysis are introduced. Then, blasting vibration signals of different blasting conditions are analysed by the wavelet packet analysis technique using MATLAB; energy distribution for different frequency bands is obtained. It is concluded that the energy distribution of blasting vibration signals varies with maximum decking charge, millisecond delay time and distances between explosion and the measuring point. The results show that the wavelet packet analysis method is an effective means for studying blasting seismic effect in its entirety, especially for constituting velocity-frequency criteria. Foundation item: Project(50490272) supported by the National Natural Science Foundation of China; project(2004036430) supported by the Postdoctoral Science Foundation of China     

小波包分析在滚动轴承信号消噪处理中的应用

对滚动轴承的故障特点进行了分析.根据小波包变换能将信号按任意时频分辨率分解到不同频段的特性,提出了小波包分解和重构用于滚动轴承信号消噪处理的概念及其算法,建立了滚动轴承加速度信号实时测试系统.通过实验研究得出,用小波包分解并通过重构可使分解后的数据长度不变,使分解层数不受限制,证明小波包分析方法应用于滚动轴承信号消噪的有效性,并取得了较好的效果.