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Modal identification of linear time periodic systems with applications to Continuous-Scan Laser Doppler Vibrometry.

机译：线性时间周期系统的模态识别及其在连续扫描激光多普勒振动测定中的应用。

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摘要

Many structures have to be modeled as Linear Time Periodic (LTP) systems to better characterize their time varying behavior, e.g., wind turbines. However, current system identification methods are mostly limited to Linear Time Invariant (LTI) systems. This work develops several frequency domain identification algorithms for LTP systems. These algorithms are completely analogous to the algorithms for LTI systems, and they are capable of extracting the modal parameters of LTP systems under any type of input, using the well-established identification routines for LTI systems. The theory includes two parts; the experimental modal analysis using the harmonic transfer function where the input is controlled and measured, and the output-only modal analysis using the harmonic power spectrum where the input is not measured but is assumed to be uniformly distributed random noise. A simplified output-only algorithm for LTP systems is also developed using the lifting approach, which groups the responses at the same time instant in a period.;The proposed modal identification algorithms are combined with a novel technique, Continuous-Scan Laser Doppler Vibrometry (CSLDV). In CSLDV, the laser continuously sweeps over a structure while measuring, capturing spatially detailed dynamic information in the same amount of time that is required by conventional methods to capture a single point. When the laser spot moves in a closed and periodic pattern on an LTI structure, the acquired velocity signal appears to be from an LTP system. Therefore, the proposed algorithms can be applied to identify modal parameters of the LTI structure. The harmonic transfer function is used to identify the operational shape of a cantilever beam under sinusoidal excitation. The speckle noise and uncertainty of CSLDV are discussed. The harmonic transfer function is also used to simultaneously measure the translational and rotational velocities of a small region by scanning a small circle around the point of interest. The harmonic power spectrum and lifting approach are used to extract the first few modes of a parked wind turbine measured with CSLDV. Finally, the harmonic power spectrum is used to extract the periodic modes of an operating turbine, which has to be modeled as a general LTP system.
机译：必须将许多结构建模为线性时间周期（LTP）系统，以更好地表征其随时间变化的行为，例如风力涡轮机。但是，当前的系统识别方法主要限于线性时不变（LTI）系统。这项工作为LTP系统开发了几种频域识别算法。这些算法与LTI系统的算法完全相似，并且能够使用成熟的LTI系统识别例程，在任何类型的输入下提取LTP系统的模态参数。该理论包括两个部分：使用谐波传递函数进行实验模态分析，其中控制和测量输入，以及使用谐波功率谱进行仅输出模态分析，其中未测量输入，但假定为均匀分布的随机噪声。还使用提升方法为LTP系统开发了一种简化的仅输出算法，该算法将一个周期中的同一时刻的响应进行分组。;提出的模态识别算法与一种新颖的技术-连续扫描激光多普勒振动法（ CSLDV）。在CSLDV中，激光在测量时连续扫过结构，以传统方法捕获单个点所需的相同时间捕获空间详细的动态信息。当激光光斑在LTI结构上以闭合且周期性的模式移动时，所获取的速度信号似乎来自LTP系统。因此，所提出的算法可以应用于识别LTI结构的模态参数。谐波传递函数用于识别正弦激励下悬臂梁的工作形状。讨论了CSLDV的斑点噪声和不确定性。谐波传递函数还用于通过扫描感兴趣点周围的小圆圈来同时测量小区域的平移和旋转速度。谐波功率谱和提升方法用于提取使用CSLDV测量的停放风力涡轮机的前几种模式。最后，谐波功率谱用于提取运行中的涡轮机的周期性模式，必须将其建模为通用LTP系统。

著录项

  • 作者

    Yang, Shifei.;

  • 作者单位

    The University of Wisconsin - Madison.;

  • 授予单位 The University of Wisconsin - Madison.;
  • 学科 Engineering Electronics and Electrical.;Applied Mechanics.;Engineering Mechanical.
  • 学位 Ph.D.
  • 年度 2013
  • 页码 200 p.
  • 总页数 200
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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