Abstract The methods for experimental modal analysis are consolidated, as are the sensors used to perform this analysis. The characteristics of the most commonly used sensors are to be “discrete” and “independent”, that is, each sensor can measure the magnitude of interest in a single point and can be placed independently from the others on the structure. This kind of layout is widely used, for example, with accelerometers, but it presents a strong complexity if the structure is extended or characterized by high modal density in the frequency range of interest, or if the number of modes to be identified is high. Often the “discrete” sensors also have nonnegligible masses compared to the mass of the structure to be analyzed, thus introducing the well-known “mass effect”. Recently, new dynamic sensors have become available based on optical fibers such as the well-known Fiber Bragg grating sensors or the more recent Optical Backscatter Reflectometry (OBR) sensors. Both are sensors of the “continuous” type, or rather, they are a succession of sensors connected in series inside a single optical fiber. The purpose of this paper is to explore the use of OBR for modal analysis and introduce an original algorithm that allows the OBR sensor to be arranged in an optimized manner, to identify up to a certain number of modes in the most effective way and to respect the constraints imposed by the optical fiber itself, such as fiber length or maximum sensor curvature. The results are illustrated by means of the experimental results obtained on a structure characterized by a simple geometry.

中文翻译：

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用于模态分析的连续传感器放置的优化：在光学背散射反射应变传感器中的应用

摘要 实验模态分析的方法以及用于执行此分析的传感器得到了巩固。最常用的传感器的特点是“离散”和“独立”，即每个传感器可以测量单个点的感兴趣的大小，并且可以独立于其他传感器放置在结构上。这种布局被广泛使用，例如加速度计，但如果结构扩展或以感兴趣的频率范围内的高模态密度为特征，或者要识别的模态数量很多，则它会呈现出很强的复杂性。与要分析的结构的质量相比，“离散”传感器通常也具有不可忽略的质量，从而引入了众所周知的“质量效应”。最近，基于光纤的新型动态传感器已经面世，例如众所周知的光纤布拉格光栅传感器或更新的光学背向散射反射计 (OBR) 传感器。两者都是“连续”类型的传感器，或者更确切地说，它们是在单根光纤内串联连接的一系列传感器。本文的目的是探索使用 OBR 进行模态分析，并介绍一种原始算法，该算法允许 OBR 传感器以优化方式排列，以最有效的方式识别一定数量的模式并尊重光纤本身施加的限制，例如光纤长度或最大传感器曲率。通过在具有简单几何形状的结构上获得的实验结果来说明结果。