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operational modal analysis of a rotating structure in an outdoor environment using a novel image-based long-range tracking continuously scanning laser Doppler vibrometer

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MEASUREMENT 2025年 253卷

作者： Lyu, Linfeng Zhu, Weidong Univ Maryland Baltimore Cty Dept Mech Engn 1000 Hilltop Circle Baltimore MD 21250 USA

This work presents the first demonstration of an image-based long-range tracking Continuously Scanning Laser Doppler Vibrometer (CSLDV) capable of operational modal analysis of rotating structures in complex outdoor environments. A differential frame technique and an edge detection algorithm are developed to address dynamic background challenges, enabling accurate vibration measurement of rotating structures under real-world conditions. The differential frame technique subtracts one frame from its neighboring frame when the camera in the image-based long-range tracking CSLDV continuously captures images of the rotating structure. The subtracted frame is the differential frame which is processed by an edge detection algorithm with a distance condition and thresholding to find locations of edges of the rotating structure. Locations of edges are used to estimate angular positions and angular velocities of the rotating structure. The misalignment between the optical axis of the camera and the rotation axis of the structure is considered when processing images to accurately generate scan paths on it using a one-dimensional scan scheme. The laser spot of the image-based long-range tracking CSLDV is swept along the scan path to measure its vibration. Measurements of the image-based long-range tracking CSLDV are processed by the improved demodulation method to estimate modal parameters, including damped natural frequencies and undamped mode shapes, of the rotating structure. Outdoor tests of tracking and scanning a rotating blade using the image-based long-range tracking CSLDV are conducted. The rotating blade is placed in front of some trees so that its background is complex and changing. The image-based long-range tracking CSLDV can accurately track and scan the rotating blade with an outdoor background, and its modal parameters are successfully estimated. The image-based long-range tracking CSLDV can be a non-contact in-situ structural health monitoring method of a rotat

关键词： Tracking continuously scanning laser Doppler vibrometer Image processing method Rotation tracking operational modal analysis

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operational modal analysis of a Hydroelectric Dam Under Mixed Excitation Conditions

Operational Modal Analysis of a Hydroelectric Dam Under Mixe...

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2023 Canadian Society for Civil Engineering Annual Conference

作者： MacLeod, Ethan Arjomandi, Kaveh MacDonald, Krista Univ New Brunswick Fredericton NB Canada NB Power Fredericton NB Canada

ISBN: (纸本)9783031615375;9783031615351;9783031615344

The safety of dams is of extreme importance, considering the high economic value and cost of failure. To assess the performance of these structures over their lifetime, vibration monitoring can be a useful tool. However, in hydroelectric generating power plants, rotating machinery can introduce harmonics into the measurements and make current methods of modal parameter estimation invalid, necessitating harmonic removal. While recent research has focused on harmonic removal in rotating mechanical machinery like wind turbines and large generators, there is a gap in understanding of monitoring gravity dams in environments with significant harmonic contamination. Most ambient vibration tests of dams have been conducted on arch and buttress-type structures, which have experienced relatively low harmonic contamination. To address this gap, a study was performed on the Mactaquac Generating Station, the largest hydroelectric power plant in the Maritime provinces, using full-scale monitoring data as part of the Mactaquac Life Achievement Project (MLAP). The study found that under low operation demand, it was possible to successfully estimate the benchmark modal parameters of the structure. However, during high operational demand, the measured signals were dominated by harmonic content, which caused several errors in the modal estimation results compared to periods of low demand. However, by reducing the harmonics in the signal, the first four mode shapes of the dam structure were successfully identified. This demonstrates that harmonics can significantly impact the accuracy of mode estimation, but their effects can be mitigated through harmonic reduction techniques.

关键词： operational modal analysis Harmonic removal Gravity dam Ambient vibration testing

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Bayesian operational modal analysis considering environmental effect

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MECHANICAL SYSTEMS AND SIGNAL PROCESSING 2025年 223卷

作者： Zhu, Yi-Chen Wu, Shan-Hao Xiong, Wen Zhang, Li-Kui Southeast Univ Sch Transportat Dept Bridge Engn Nanjing Peoples R China Anhui Transportat Holding Grp Co Ltd Hefei Peoples R China

In long term structural health monitoring (SHM), operational modal analysis (OMA) techniques are commonly used to identify dynamic properties of structures. However, conventional OMA methods do not consider the effect of environment, which may cause bias in the identified dynamic properties. Some machine learning models (such as Gaussian process model) can quantitatively describe the effect of environment on structure, but the associated parameters do not have physical meaning. In order to address these problems, this paper proposes a novel fusion model that combines structural dynamics model and data-driven model to identify dynamic properties with the effect of environment considered. The proposed method adopts a probabilistic framework that can incorporate the uncertainties and correlations in the data. The proposed method is validated using synthetic data and applied to the monitoring data of two full-scale bridges. The results show that it can effectively identify the modal parameters while describing the correlation between the environmental variations and the structural responses. The proposed method can facilitate robust and reliable identification of dynamic properties with structures under environmental effect.

关键词： Bridge structural monitoring Gaussian Process Environmental Variation Bayesian inference operational modal analysis

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Damage detection and localization method for wind turbine rotor based on operational modal analysis and anisotropy tracking

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MECHANICAL SYSTEMS AND SIGNAL PROCESSING 2025年 224卷

作者： Cadoret, Ambroise Denimal-Goy, Enora Leroy, Jean-Marc Pfister, Jean-Lou Mevel, Laurent IFP Energies Nouvelles F-69360 Solaize France Univ Gustave Eiffel Inria COSYS SII I4S F-35042 Rennes France IFP Energies Nouvelles F-92852 Rueil Malmaison France

Subspace-based damage detection methods are widely used for civil engineering structures modeled as linear time-invariant systems. For operating wind turbines modeled as linear time- periodic systems, these methods cannot be theoretically used, due to the inherent assumptions associated with these methods in the context of linear time-invariant systems. Based on a model approximation of time-periodic systems as time-invariant ones, these methods can still be applied and adapted to perform change detection for time-periodic systems, through a Gaussian residual built upon damage sensitive parameters coming from the identified modal parameters. The proposed method is tested and validated on data simulated with an aero-servo-elastic model of an operating wind turbine, with the detection of local stiffness reductions on a blade and the localization of the damaged blade. Furthermore, two selections of sensors are tested, to evaluate the impact of the sensor choice on the performance of the detection and localization methods.

关键词： Damage detection Wind turbine Vibration measurements Statistical tests operational modal analysis

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modal Complexity Factors as indexes for modal parameter identification in operational modal analysis of coupled dynamic systems

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JOURNAL OF SOUND AND VIBRATION 2025年 600卷

作者： Ibarrola-Chamizo, J. Agirre-Olabide, I. Merino, M. Aginaga, J. Publ Univ Navarre UPNA Engn Dept Arrosadia Campus Pamplona 31006 Spain Inst Smart Cities ISC Arrosadia Campus Pamplona 31006 Spain

Vibration analysis seeks to extract the modal parameters of a mechanical system by means of experimental measurements. Natural frequencies, damping ratios and mode shapes are identified from the measurements data from experimental or operational modal analysis. modal shapes can show real or complex values. The degree of complexity of a modal shape can be measured by the modal Complexity Factors (MCF). Among others, modal complexity can be due to non-uniformly distributed damping. In complex mechanical systems like a robot, complex modes are expected due to its active and non distributed damping. In turn, in a metallic workpiece real modes are expected. In the robotic machining of thin workpieces, both the robot and the workpiece constitute a coupled dynamic system, operating within the same frequency range. This work proposes the use of MCFs as indexes to determine if each mode corresponds to the workpiece or the robot. Experimental results of an operational modal analysis show a lower mode complexity for the workpiece modes and a higher complexity for the robot frequencies. MCFs show a good performance in separating modes of such coupled systems due to the different damping nature of the robot and the workpiece.

关键词： modal Complexity Factor modal parameter identification operational modal analysis Stochastic Subspace Identification Robotic machining

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Assessment of damping in monopile-supported offshore wind turbines: Integrating operational modal analysis with regression techniques

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STRUCTURES 2025年 75卷

作者： Xi, Yibo Zhang, Xin Pan, Jianing Sun, Liyun Li, Hao Wang, Zhenyu Zhejiang Univ Coll Civil Engn & Architecture Hangzhou 310058 Peoples R China

The identification of damping sources in the design of offshore wind turbine (OWT) structures has been approached in many different ways. Among all the methods, assessing damping sources based on monitoring data for OWT operations is more reliable compared to using experimental or empirical techniques. This study aims to perform an automated operational modal analysis of an instrumented OWT using detailed vibration monitoring to effectively assess different sources of damping. Firstly, continuous vibration acceleration of a monopile-supported utility-scale OWT is measured to obtain mode parameters by operational modal analysis. An automated modal identification method is designed to obtain mode parameters from a large of monitoring data. The natural frequency and damping ratio of both the first and second order bending modes of the OWT tower are observed. Besides, the characteristics of these mode parameters during the OWT operation are analysed. A datadriven damping assessment method is then introduced to access aerodynamic, hydrodynamic and structural damping. This assessment method is based on the identified damping from operational modal analysis, and it separates the different damping sources with regression techniques. The proposed assessment method provides a practical way to understand the damping sources of OWTs which is meaningful for the structural design. Furthermore, the method also holds potential applicability for damping assessment in various types of OWTs.

关键词： Offshore wind turbine Damping assessment operational modal analysis Natural frequency Vibration measurement

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Distributed operational modal analysis of Multispan Bridges

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JOURNAL OF BRIDGE ENGINEERING 2025年第5期30卷

作者： Morgese, Maurizio Wang, Chengwei Taylor, Todd Ansari, Farhad Rutgers State Univ Sch Engn Ctr Adv Infrastruct & Transportat 100 Brett Rd Piscataway NJ 08854 USA Univ Illinois Dept Civil Mat & Environm Engn Smart Sensors & NDT Lab 842W Taylor St Chicago IL 60607 USA

A method is presented for estimating the mode shapes of multispan structures based on the distributed optical fiber strain sensors. The dynamic mode decomposition method was employed to decompose the spatial-temporal strain data into strain modes. The approach was developed and verified through laboratory experiments on a three-span 15-m-long steel beam, field tests on a five-span bridge, and numerical modeling based on the finite-element analysis of the bridge. A Brillouin-based distributed optical fiber sensor system was utilized in laboratory and field settings. In addition, conventional piezoelectric-based accelerometers were employed to compare with the modal parameter estimations based on the distributed strains. The bridge's first three flexural vibration modes were extracted by using the introduced methodology. Further testing and analysis are necessary to evaluate its feasibility across different bridge designs, such as single-span, cable-stayed, arch, and suspension bridges.

关键词： Dynamic mode decomposition Structural health monitoring (SHM) Brillouin optical time-domain analysis (BOTDA) Distributed strain operational modal analysis Output-only modal analysis Bridge operational conditions Structural assessment Fiber optic sensors FEM

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Automatic operational modal analysis for concrete arch dams integrating improved stabilization diagram with hybrid clustering algorithm

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MECHANICAL SYSTEMS AND SIGNAL PROCESSING 2025年 224卷

作者： Wu, Yingrui Kang, Fei Wan, Gang Li, Hongjun Dalian Univ Technol Sch Infrastruct Engn Dalian 116024 Peoples R China China Yangtze Power Co Ltd Yichang 443000 Peoples R China China Inst Water Resources & Hydropower Res State Key Lab Simulat & Regulat Water Cycle River Beijing 100048 Peoples R China

modal identification based on ambient vibration has gained increasing importance in monitoring the operational behavior of dams. This paper develops a robust automated modal identification method to identify the modal parameters of concrete dams. The proposed method requires no modal validation criteria beyond some widely used thresholds. Initially, the covariance-driven stochastic subspace identification (SSI-COV) algorithm is utilized to extract modal parameters, then introducing an improved stabilization diagram to eliminate spurious modes. Subsequently, a hybrid clustering algorithm that combines the clustering by fast search and find of density peaks (DPC) algorithm with a shared nearest neighbor approach is proposed to group physical modes. Clustering centers are determined automatically through a statistics-based method. Finally, the boxplot method is employed to detect and remove outliers from each cluster, thereby facilitating more accurate modal parameter estimation. The performance of the proposed method is validated by identifying the modal parameters of a five-degree-of-freedom frame model and a small-scale arch dam. The results demonstrate that the proposed method is capable of automatically identifying modal parameters with considerable accuracy and robustness.

关键词： Arch dams Automated identification operational modal analysis Stabilization diagram Density peaks clustering

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De-mixing variational mode decomposition and its application on operational modal analysis in the presence of closely spaced modes

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MEASUREMENT 2025年 242卷

作者： Jian, Jiawei Lu, Zhong-Rong Liu, Jike Wang, Li Sun Yat Sen Univ Sch Aeronaut & Astronaut Guangzhou Peoples R China

Variational mode decomposition (VMD), and its derivative methods have been demonstrated to be promising signal decomposition tools and widely utilized in modal analysis. However, they inevitably suffer from mode mixing sometimes, greatly impairing the quality of decomposition. This paper proposes a pair of novel VMD-based methods for univariate signal and multivariate signal respectively, referred to as de-mixing VMD (D-VMD) and de-mixing multivariate VMD (D-MVMD), which can greatly alleviate mode mixing in decomposition. The ensemble correlation coefficient is defined to evaluate the correlatedness between one mode and others and then involved in the variational formulation as an additional Lagrangian multiplier item to enhance the constraint in terms of mode mixing. Additionally, anew scheme is proposed to robustly identify modal parameters from the decomposed modal responses. Numerical simulations and a pedestrian bridge were investigated to validate the effectiveness of the proposed methods in identifying closely spaced modes.

关键词： Variational mode decomposition operational modal analysis Mode mixing Lagrangian multiplier Multivariate signal processing

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operational modal analysis of a liquid-filled cylindrical structure with decreasing filling mass by multivariate stochastic parameter evolution methods

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INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES 2020年 172卷 105420-105420页

作者： Ma, Zhi-Sai Ding, Qian Tang, Ye Tianjin Univ Sch Mech Engn Tianjin 300350 Peoples R China Anhui Polytech Univ Sch Mech & Automot Engn Wuhu 241000 Peoples R China Tianjin Key Lab Nonlinear Dynam & Control Tianjin 300350 Peoples R China

Variable mass structures exhibit non-stationary characteristics and the corresponding time-varying (TV) dynamics are difficult to represent by explicit dynamic equations or finite element models via mechanism analysis. operational modal analysis of variable mass structures based on vector response measurements is considered in this paper. In order to solve the practical problem of operational modal analysis for variable mass structures, univariate stochastic parameter evolution (SPE) methods are extended to the multivariate case and validated by a numerical varying mass system. Thereafter, a laboratory liquid-filled cylindrical structure with decreasing filling mass is built and analyzed by using the conventional "frozen-configuration" technique and non-parametric time-frequency analysis method. Finally, the multivariate SPE method is applied to identify the liquid-filled cylindrical structure with decreasing filling mass, and identification results demonstrate that the proposed method is able to obtain the TV dynamic characteristics of variable mass structures under operating conditions by only using the available vector response measurements.

关键词： operational modal analysis Variable mass structures Liquid-filled cylindrical structure Time-varying system identification

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