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为解除载荷识别问题对原系统先验知识的依赖,本文提出采用最小二乘支持向量机(Least squares support vector machine,LS-SVM)对非线性系统进行逆模型辨识,随后在该逆模型基础上利用工作状态的响应数据识别时域载荷。通过对某一非线性系统的稳态和非稳态激励的仿真计算,验证了该方法的有效性。仿真结果表明LS-SVM能够辨识出可靠的非线性系统的逆模型,进而反演出较精确的时域载荷。该方法不需要了解系统的数学模型及参数,只需少量训练样本即可,因此该方法能够应用于工程实践中。 相似文献
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无迹卡尔曼滤波(UKF)是一种识别非线性系统的有效方法,然而传统的UKF方法需要观测外部激励,这限制了UKF的应用范围。迄今为止,国内外对未知激励情况下的UKF方法的研究还非常少。该文在传统UKF的基础上,推导出在未知激励情况下的无迹卡尔曼滤波(UKF-UI)方法的递推公式,通过对观测误差的最小化,利用非线性方程求解,识别未知外部激励,进而识别非线性结构系统状态与结构未知参数。进一步采用融合部分观测的加速度响应及位移响应,消除识别结果的漂移问题。分别通过白噪声和未知地震作用下识别非线性迟滞模型的两个数值算例,考虑观测噪声对非线性系统进行识别,从而验证提出新方法的有效性。结果表明,该文所提出的UKF-UI方法,能够在部分观测结构系统响应的情况下,有效地识别非线性结构参数和未知激励。 相似文献
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假定任意随机激励信号由白噪声与非白噪声信号组成,由此导出线性结构响应之间的相关函数由两部分组成,一部分与脉冲响应具有相同的数学形式,另一部分为其它形式.利用模态分解法的基本原理,把相关函数分解为各个模态函数的叠加与余项之和.这样,第一部分信号已经分解为不同的模态函数,第二部分中的周期信号也变成了模态函数.这就把非稳态环境激励下多自由度线性结构系统的模态参数辨识问题转化为类似于已知各个单自由度系统的脉冲响应进行参数辨识问题.理论和模拟实验及斜拉桥模型参数辨识实例表明,已成功地利用模态分解法进行非稳态环境激励下多自由度线性结构系统的模态参数辨识.其主要优点:一是无论是白噪声激励、稳态随机激励还是非稳态随机激励,仅根据结构的响应辨识线性结构的模态参数;二是能有效地识别出环境激励中的周期成分. 相似文献
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非稳态环境激励下线性结构的模态参数辨识 总被引:12,自引:2,他引:12
假定任意随机激励信号由白噪声与非白噪声信号组成,由此导出线性结构响应之间的相关函数由两部分组成,一部分与脉冲响应具有相同的数学形式,另一部分为其它形式,利用模态分解法的基本原理,把相关函数分解为各个模态函数的叠加与余项之和,这样,第一部分信号已经分解为不同的模态函数,第二部分中的周期信号也变成了模态函数,这就把非稳态环境激励下多自由度线性结构系统的模态参数辨识问题转化为类似于已知各个单自由度系统的脉冲响应进行模态参数辨识问题,理论和模拟实验表明,本文成功地利用模态分解法进行非稳态环境激励下多自由度线性结构系统的模态参数辨识,其主要优点是,无论是白噪声激励,稳态随机激励还是非稳态随机激励,仅根据结构的响应不仅能辨识线性结构的模态参数,而且能有效地识别出环境激励中的周期成分。 相似文献
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对结构进行模态分析时,若被测结构同时存在人工激励和环境噪声激励,充分利用噪声响应可以得到更优结果。基于无参数噪声模型,提出一种计及噪声激励的试验模态参数识别方法。由谱分析法计算出噪声响应的自谱-互谱矩阵,然后根据Hilbert变换理论估计出仅噪声响应的类频率响应函数。将该函数用于扩充基于人工激励估计出的频率响应函数矩阵,并使用多参考点最小二乘复频域法识别出结构模态参数。采用弯扭二自由度机翼模型仿真算例和飞机模型实测算例,对该方法的可靠性进行了验证。将所提方法与传统方法比较,结果表明:该方法更可靠、参数识别更准确。 相似文献
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环境激励下基于小波变换和奇异值分解的结构模态参数识别 总被引:1,自引:0,他引:1
采用小波变换和奇异值分解相结合的方法对环境激励下结构的模态参数进行识别.首先对环境激励下的时不变结构的加速度响应进行协方差分析得到时域协方差响应,利用小波变换将协方差响应转换到时/频域中,沿每一个尺度点提取协方差响应的小波系数阵,然后对提取的小波系数阵进行奇异值分解得到奇异值和奇异向量,最后从重构的奇异值和奇异向量中识别出结构的模态参数.文章通过3自由度系统数值算例分析了该方法的抗噪性能,结果表明该方法具有很好的抗噪能力,在15 dB噪声干扰下能够稳定和准确地识别出结构的模态参数,且比直接用小波变换方法识别的结果更准确;并通过东海大桥主航道斜拉桥模态参数识别的例子进一步验证该方法的实际应用可行性. 相似文献
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《振动与冲击》2017,(15)
基于振动的土木工程结构系统识别中,常用的识别方法如基于Newmark-β算法的方法,常常需要已知激励,而事实上激励和完整的输出响应是很难测得的。基于此,在现有的Newmark-β算法中引入多项式拟合来解决结构系统识别误差带来的漂移现象,进而提出了改进的Newmark-β算法,并结合改进协同粒子群算法(IMPSCO),给出了仅用部分结构响应的系统识别和激励辨识方法。最后,通过一七层钢框架数值算例和实验室模型试验验证了方法的有效性和可行性,并探讨了噪声、输出响应完整性的影响。研究表明,所提方法能准确地实现未知激励和部分实测响应状态下的结构系统和未知激励的识别,而且具有较强的容噪性和鲁棒性。 相似文献
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一种用于主动噪声抑制系统的次级通道特性识别算法的改进 总被引:1,自引:0,他引:1
本文着重研究窄带信号噪声自适应主动抑制技术中的次级通道特性在线识别问题。针对窄带噪声信号,提出了基于自适应陷波器的次级通道特性在线识别算法,该方法利用自适应陷波器技术解决在线识别时存在的激励信号干扰问题,从而提高次级通道特性在线识别的速度。同时研究了选定参数对算法性能的影响。仿真结果表明,基于自适应陷波器的次级通道特性在线识别算法能较大程度的提高对次级通道特性的识别速度。 相似文献
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Thomas‐Peter Fries Andreas Zilian 《International journal for numerical methods in engineering》2009,79(1):69-93
The extended finite element method (XFEM) is often used in applications that involve moving interfaces. Examples are the propagation of cracks or the movement of interfaces in two‐phase problems. This work focuses on time integration in the XFEM. The performance of the discontinuous Galerkin method in time (space–time finite elements (FEs)) and time‐stepping schemes are analyzed by convergence studies for different model problems. It is shown that space–time FE achieve optimal convergence rates. Special care is required for time stepping in the XFEM due to the time dependence of the enrichment functions. In each time step, the enrichment functions have to be evaluated at different time levels. This has important consequences in the quadrature used for the integration of the weak form. A time‐stepping scheme that leads to optimal or only slightly sub‐optimal convergence rates is systematically constructed in this work. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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Gaigerov B. A. Elkin G. A. Zagirova E. G. Kostromin V. P. Koshelyaevskii N. B. Pushkin S. B. 《Measurement Techniques》2005,48(1):5-15
The structure of the standard time and frequency basis of the State Service for Time and Frequency (SSTF) of Russia is described. Information is given for the equipment make-up for the state primary standard of time and frequency (STFS) of the Russian Federation and secondary standards (SS) of the STFS. The most important metrological characteristics of the STFS and SS are provided.Translated from Izmeritelnaya Tekhnika, No. 1, pp. 12–18, January, 2005 相似文献
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K. K. Tamma X. Zhou D. Sha 《International journal for numerical methods in engineering》2001,50(7):1619-1664
A standardized formal theory of development/evolution, characterization and design of a wide variety of computational algorithms emanating from a generalized time weighted residual philosophy for dynamic analysis is first presented with subsequent emphasis on detailed formulations of a particular class relevant to the so‐called time integration approaches which belong to a much broader classification relevant to time discretized operators. Of fundamental importance in the present exposition is the evolution of the theoretical design and the subsequent characterization encompassing a wide variety of time discretized operators, and the proposed developments are new and significantly different from the way traditional modal type and a wide variety of step‐by‐step time integration approaches with which we are mostly familiar have been developed and described in the research literature and in standard text books over the years. The theoretical ideas and basis towards the evolution of a generalized methodology and formulations emanate under the umbrella and framework and are explained via a generalized time weighted philosophy encompassing single‐field and two‐field forms of representations of the semi‐discretized dynamic equations of motion. Therein, the developments first leading to integral operators in time, and the resulting consequences then systematically leading to and explaining a wide variety of generalized time integration operators of which the family of single‐step time integration operators and various widely recognized and new algorithms are subsets, the associated multi‐step time integration operators and a class of finite element in time integration operators, and their relationships are particularly addressed. The generalized formulations not only encompass and explain a wide variety of time discretized operators and the recovery of various original methods of algorithmic development, but furthermore, naturally inherit features for providing new avenues which have not been explored an/or exploited to‐date and permit time discretized operators to be uniquely characterized by algorithmic markers. The resulting and so‐called discrete numerically assigned [DNA] markers not only serve as a prelude towards providing a standardized formal theory of development of time discretized operators and forum for selecting and identifying time discretized operators, but also permit lucid communication when referring to various time discretized operators. That which constitutes characterization of time discretized operators are the so‐called DNA algorithmic markers which essentially comprise of both (i) the weighted time fields introduced for enacting the time discretization process, and (ii) the corresponding conditions these weighted time fields impose (dictate) upon the approximations (if any) for the dependent field variables in the theoretical development of time integrators and the associated updates of the time discretized operators. Furthermore, a single analysis code which permits a variety of choices to the analyst is now feasible for performing structural dynamics computations on modern computing platforms. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
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本文对果蔬装配式冷库稳定运行阶段进行实验研究,测试冷库在不同环境温度下的开、停机时间,建立冷库稳定运行阶段开、停机时间和工作时间系数数学模型,运用MATLAB编程计算装配式冷库在不同夹心板厚度和不同制冷系统配置下的工作时间系数。结果表明:开、停机时间数学模型经修正后,开机时间最大误差由11.6%减小到2.78%,停机时间的计算值最大误差由7.91%减小到1.46%,大大提高了开、停机时间计算精度。工作时间系数模型计算值与实验值最大误差在3.47%以内,果蔬装配式冷库稳定运行阶段工作时间系数数学模型具备工程应用精度。相同环境温度下,随制冷系统制冷量的增加,工作时间系数减小幅度越来越小,制冷剂流量界限选择0.012 kg/s较为合适。随库板厚度的增加,工作时间系数减小幅度越来越小,保温体一次投资也相应增加,从经济性角度考虑,对使用时间较短的临时性冷库,保温层厚度按推荐值100 mm即可,冷库使用时间较长时,保温层厚度在100 mm基础上可以适当增加。 相似文献