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Quantifying and managing uncertainty in operational modal analysis

机译：量化和管理运营模式分析中的不确定性

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摘要

Operational modal analysis aims at identifying the modal properties (natural frequency, damping, etc.) of a structure using only the (output) vibration response measured under ambient conditions. Highly economical and feasible, it is becoming a common practice in full-scale vibration testing. In the absence of (input) loading information, however, the modal properties have significantly higher uncertainty than their counterparts identified from free or forced vibration (known input) tests. Mastering the relationship between identification uncertainty and test configuration is of great interest to both scientists and engineers, e.g., for achievable precision limits and test planning/budgeting. Addressing this challenge beyond the current state-of-the-art that are mostly concerned with identification algorithms, this work obtains closed form analytical expressions for the identification uncertainty (variance) of modal parameters that fundamentally explains the effect of test configuration. Collectively referred as 'uncertainty laws', these expressions are asymptotically correct for well-separated modes, small damping and long data; and are applicable under non-asymptotic situations. They provide a scientific basis for planning and standardization of ambient vibration tests, where factors such as channel noise, sensor number and location can be quantitatively accounted for. The work is reported comprehensively with verification through synthetic and experimental data (laboratory and field), scientific implications and practical guidelines for planning ambient vibration tests.
机译：操作模态分析旨在仅使用在环境条件下测得的（输出）振动响应来识别结构的模态特性（固有频率，阻尼等）。高度经济和可行，这已成为全面振动测试中的一种常见做法。但是，在没有（输入）载荷信息的情况下，模态特性的不确定性要比从自由振动或强制振动（已知输入）测试中确定的对应特性高得多。科学家和工程师都对掌握识别不确定性和测试配置之间的关系非常感兴趣，例如，对于可实现的精度限制和测试计划/预算。除了当前主要与识别算法有关的最新技术之外，这项工作还解决了这一难题，这项工作获得了模态参数识别不确定性（方差）的闭式分析表达式，从根本上解释了测试配置的效果。这些表达式统称为“不确定性定律”，对于模式分离，阻尼小和数据长的情况，渐近正确。并且适用于非渐近情况。它们为规划和标准化环境振动测试提供了科学依据，其中可以量化考虑通道噪声，传感器数量和位置等因素。通过合成和实验数据（实验室和现场），科学意义和规划环境振动测试的实用指南，对工作进行了全面报告。

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