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MODAL PARAMETERS EXTRACTION WITH CROSS CORRELATION FUNCTION AND CROSS POWER SPECTRUM UNDER UNKNOWN EXCITATION 总被引:2,自引:1,他引:1
Artificial excitation is the most employedtype,but it is not suitable for some large- scalestructures such as platforms,bridges and build-ings,because a sufficient amount of excitation en-ergy can be needed to vibrate these structures,andthat impliesthe dangerofdamaging them locally orglobally.So natural excitation ( such as wind,wave,and traffic excitation) can be used in thesecases.However,a measure of the input force be-ing applied to the systems is not available and onlythe response can be… 相似文献
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基于随机激励的某机匣模态实验与分析 总被引:10,自引:1,他引:9
用模态实验的方法对某型飞机发动机机匣的模态参数进行了识别。考虑噪声对频响函数的影响,在功率谱分析时,导出了噪声影响情况下的功率谱表达式,利用这个表达式计算了频响函数并最终用来提取模态参数。引入预实验方法用于机匣模态参数的探测中,以确定机匣上各个测点和激振器激振点的合理布置。考虑到实际工作时的激励情况,在实验台上用白噪声随机激励来模拟环境激励,对机匣进行了模态实验。与计算模态相比,用实验模态方法提取模态参数,避免了复杂的有限元建模与仿真,并能用相干函数来检验测得的实验数据的有效性。实验模态分析表明,得到的模态参数对于进一步改进机匣设计、分析其振动、疲劳寿命特性等具有重要的意义。 相似文献
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运行模态分析的频域空间域分解法及其应用 总被引:7,自引:0,他引:7
提出了一种基于频域空间域分解(Frequency and Spatial Domain Decomposition, FSDD)的运行模态分析方法。该法将同时具有输入和输出的试验模态分析的经典方法——复模态指示因子(Complex Mode Indicator Function, CMIF)法拓展到了仅有输出响应的运行状态模态分析。FSDD法采用奇异值分解将信号空间和噪声空间分离开来,把奇异值曲线作为模态指示的依据,以奇异值向量作为加权函数得到每一阶模态的增强功率谱(Power Spectrum Density, PSD),进而在频域内对增强PSD曲线进行最小二乘拟合以得到准确的模态频率和阻尼参数。采用了一个二层楼仿真算例和在欧洲广为人知的瑞士Z24公路大桥实测算例来验证FSDD算法。 相似文献
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介绍了脉冲激励法(锤击法)模态试验系统。该法设备简单,使用方便,移动施力部位容易,可以在不允许安装激振器的部位实现激振,具有许多明显的优点。试验结果可提供给导弹总体设计部门,以检验发动机与弹体配匹的结构动态特性,并可供发动机振动分析之用。 相似文献
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用脉冲激励法对某发动机前轴承弹性支承进行了试验模态分析,并介绍了试验模态 方法和设备,所得模态分析结果表明,相干函数值均大于0.9,弹性支承的固有频率,振型符合发动机结构设计要求。 相似文献
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为准确获取离心叶轮叶片的高阶振动特性及其模态,利用压电纤维复合材料(Marco fiber composite,MFC)对离心叶轮叶片进行模态测试。设计了MFC激励系统,提出了MFC选型、激励和测点位置的确定方法,研究了不同信号的高阶模态激励效果,并分析了MFC附加质量和刚度对叶片固有频率和模态的影响;结合有限元仿真结果,对比分析了前20阶振动模态的异同。试验结果表明:MFC具有操作简单、重复性好、信噪比高、能够稳定激励出高阶模态等优势,计算模态与测量模态吻合较好,在第6~8阶与第12~15阶之间存在模态密集区域;MFC附加质量和刚度对实验固有频率的影响低于4%。提出的MFC激励方法可用于具有较高固有频率的航空发动机部件的模态测量。 相似文献
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Generation of Non-Gaussian Random Vibration Excitation Signal for Reliability Enhancement Test 总被引:3,自引:0,他引:3
YU Ying-yang JIANG Tong-min 《中国航空学报》2007,20(3):236-239
During environment testing, the time histories of some dynamic environments follow non-Gaussian distribution. It is always assumed that the random vibration simulated follows Gaussian distribution, because the traditional digital random vibration control system can only supply the random vibration excitation signal of Gaussian. Yo simulate the real environment of product, a method is developed in this paper that can generate non-Gaussian random signal with specified power spectrum density (PSD), skewness and kurtosis by shot noise. In this way, non-Gaussian random vibration can be produced on traditional electrodynamic shaker. It solves the problems of spectral valley and energy shortage in low frequency on omni-axis shaker. At last, the wavelet is used to analyze the non-Gaussian signal 相似文献
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随机噪声载荷作用下薄壳结构的随机振动实验研究 总被引:1,自引:1,他引:0
为研究薄壁壳结构在随机噪声激励下的随机振动响应特征,本文设计了一套针对薄壁壳在内部随机噪声作用下的振动问题进行研究的实验方案,同时对噪声载荷和薄壳振动加速度响应进行测量,并对实验结果进行初步的定性分析,了解噪声载荷在频率域上的分布特征和薄壁壳在内部随机噪声作用下的振动响应特征,获得在噪声激励的频率范围内能激起薄壳该频率范围内所有模态共振等结论,为薄壳结构在内部噪声作用下随机振动响应的计算方法的研究提供依据。 相似文献
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本文简要地论述了机械设备故障振动诊断的理论基础,进而基于理论上的分析及作者个人的经验,对旋转机械故障振动诊断的前景作了评述,提出了若干建议。 相似文献
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Spectral Moment Estimates from Correlated Pulse Pairs 总被引:1,自引:0,他引:1
Estimates statistics of the first two power spectrum moments from the pulse pair covariance are analyzed. The input signal is assumed to be colored Gaussian and the noise, white Gaussian. Perturbation formulas for the standard deviation of both mean frequency and spectrum width are applied to a Gaussian shaped power spectrum, and so is a perturbation formula for the bias in the width estimate. Mean frequency estimation from interlaced pulse pairs is presented. Throughout this study, estimators from independent, spaced, and contiguous pulse pairs are compared to provide a continuum of statistics from equispaced tightly correlated to statistically independent pulse pairs. 相似文献
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针对传统有限元建模黑箱操作多、计算成本大、不具有自主知识产权等问题,基于经典层合板理论,随机振动理论和Miner线性积累损伤准则,建立了基础随机激励下纤维增强复合薄板振动疲劳寿命预测的解析模型。基于应力模态法,推导了纤维增强复合薄板的应力频响函数,在考虑随机激励的基础上,得到了结构的随机振动等效应力功率谱密度函数。通过Dirlik、Bendat和Benasciutti-Tovo三种频域模型对应的概率密度函数,成功求解了相应的振动疲劳寿命。另外,采用ANSYS与nCode软件对模型及其预测结果的正确性进行了验证,研究发现该模型寿命计算结果相对于商业软件计算结果的偏差不超过14.8%,但计算效率提高了17%~33%。因此,该模型可为预测随机激励下各向异性复合薄板的振动疲劳问题,提供一种思路和工具。 相似文献
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Jouny I. Garber E.D. Moses R.L. 《IEEE transactions on aerospace and electronic systems》1995,31(1):69-77
Radar target identification is performed using time-domain bispectral features. The classification performance is compared with the performance of other classifiers that use either the impulse response or frequency domain response of the unknown target. The classification algorithms developed here are based on the spectral or the bispectral energy of the received backscatter signal. Classification results are obtained using simulated radar returns derived from measured scattering data from real radar targets. The performance of classifiers in the presence of additive Gaussian (colored or white), exponential noise, and Weibull noise are considered, along with cases where the azimuth position of the target is unknown. Finally, the effect on classification performance of responses horn extraneous point scatterers is investigated 相似文献
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Sonnenschein A. Fishman P.M. 《IEEE transactions on aerospace and electronic systems》1992,28(3):654-660
The standard analysis of the radiometric detectability of a spread-spectrum signal assumes a background of stationary, white Gaussian noise whose power spectral density can be measured very accurately. This assumption yields a fairly high probability of interception, even for signals of short duration. By explicitly considering the effect of uncertain knowledge of the noise power density, it is demonstrated that detection of these signals by a wideband radiometer can be considerably more difficult in practice than is indicated by the standard result. Worst-case performance bounds are provided as a function of input signal-to-noise ratio (SNR), time-bandwidth (TW) product and peak-to-peak noise uncertainty. The results are illustrated graphically for a number of situations of interest. It is also shown that asymptotically, as the TW product becomes large, the SNR required for detection becomes a function of noise uncertainty only and is independent of the detection parameters and the observation interval 相似文献