Operational modal analysis in the presence of harmonic excitations by the use of transmissibility measurements

Devriendt, Christof; Sitter, Gert De; Vanlanduit, Steve; Guillaume, Patrick

doi:10.1016/j.ymssp.2008.07.009

Cited by 102 publications

(45 citation statements)

References 9 publications

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“…Canales et al [73] studied the output-only modal identification using transmissibility under variable load conditions. Devriendt et al [74][75][76] used transmissibility to identify modal parameters from output-only transmissibility measurements and multivariable transmissibility measurements. Chesne and Deraemaeker [77] reviewed the state-of-the-art of using transmissibility functions for damage localization of mechanical systems.…”

Section: Frequency Domain Methodsmentioning

confidence: 99%

The State-of-the-Art on Framework of Vibration-Based Structural Damage Identification for Decision Making

2017

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Abstract:Research on detecting structural damage at the earliest possible stage has been an interesting topic for decades. Among them, the vibration-based damage detection method as a global technique is especially pervasive. The present study reviewed the state-of-the-art on the framework of vibration-based damage identification in different levels including the prediction of the remaining useful life of structures and the decision making for proper actions. This framework consists of several major parts including the detection of damage occurrence using response-based methods, building reasonable structural models, selecting damage parameters and constructing objective functions with sensitivity analysis, adopting optimization techniques to solve the problem, predicting the remaining useful life of structures, and making decisions for the next actions. For each part, the commonly used methods were reviewed and the merits and drawbacks were summarized to give recommendations. This framework is aimed to guide the researchers and engineers to implement step by step the structure damage identification using vibration measurements. Finally, the future research work in this field is recommended.

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Section: Frequency Domain Methodsmentioning

confidence: 99%

The State-of-the-Art on Framework of Vibration-Based Structural Damage Identification for Decision Making

2017

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“…Therefore, applications using the conventional OMA technique encounter difficulties in correctly identifying modal parameters; this is due to the influence of nonrandom forces. In recent years, researchers have proposed an improved OMA method that is based on transmissibility measurements and does not require any assumptions about the nature of system excitations (Devriendt and Guillaume, 2008;Devriendt et al, 2009 …”

Section: Operational Modal Analysismentioning

confidence: 99%

A Novel method based on operational modal analysis for monitoring the preload degradation of linear guideways in machine tools

Tsai

Cheng²,

Cheng

2017

Mechanical Engineering Journal

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A novel method for automatically monitoring the preload degradation of linear guideway type (LGT) recirculating linear ball bearings of an X-Y table is proposed. Both simulations and experiments revealed that the reduction in the natural frequency corresponding to the yawing mode of the worktable was extremely sensitive to and varied linearly with the degradation of the LGT linear bearing preload. By attaching three accelerometers to the worktable of a machine tool and then exciting the worktable with a pulse from the servo motor of a feed drive, this study identified the natural frequencies of the worktable and their corresponding mode shapes by using operational modal analysis (OMA). Among all the natural frequencies obtained by OMA, the natural frequency corresponding to the specific yawing mode of the worktable was extracted using the modal assurance criteria, and the change in the extracted frequency was tracked; thus, the degradation of LGT linear bearing preload could be monitored automatically without exciting the worktable manually. In this study, the performance of this method was assessed experimentally, and this paper presents the method in detail.

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“…• Input spectrum independent techniques: these techniques deliver an identification of the modal parameters which is independent of the input spectrum and thus unaffected by the input coloration, for instance transmissibility based OMA (TOMA) [10] and poly-reference TOMA (pTOMA) [11].…”

Section: Available Techniques and Common Assumptionsmentioning

confidence: 99%

Operational Modal Analysis in the Presence of Harmonic Excitations: A Review

Motte

Weijtjens

Devriendt

et al. 2015

Conference Proceedings of the Society for Experimental Mechanics Series

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Over the past years the use of Operational Modal Analysis (OMA) for Structural health monitoring has become more and more widespread. Such a methodology would also be relevant to wind farm owners that want to monitor the integrity of their turbines' foundations.However, harmonic components, originating from the rotor and periodic aerodynamic forces, are present within the measured vibrations. The harmonics violate the set of assumptions of common OMA techniques and as a result, these techniques potentially fail. This paper explores the different techniques presented in the literature to handle these harmonics. The techniques are first presented and later applied on data of an offshore wind turbine in the Belgian North Sea. Keywords IntroductionTo identify the modal parameters of a structure modal analysis can be used. If the considered structure is small enough experimental modal analysis (EMA) [1] is applicable. In this case the experiment is carried out on a laboratory scale and a known excitation is applied to the structure. Both the excitation and the response of the structure are measured. For larger structures applying a known excitation to the structure becomes more difficult and operational modal analysis (OMA) [2] can be a good alternative to EMA. In this case the excitation is ambient and cannot be measured. Therefore, in order to carry out the identification, a set of assumptions needs to be made [1]. Modal analysis requires that the whole frequency band of interest is excited; the system is linear and time invariant. OMA furthermore requires that the excitation is steady state random white noise. The main advantage of OMA is that the modal parameters are identified under operational conditions, e.g. the blade of a wind turbine becomes stiffer if the rotational velocity is larger [3]. Moreover, the system can be studied on a continuous basis, which is important if one wants to monitor the health of the structure. The boundary conditions can also be difficult to be reproduced if EMA is used. Therefore OMA can be used to continuously monitor the integrity of the offshore wind turbine [4] and several bridges in Portugal [2].Due to the rotor harmonics and periodic aerodynamic effects the excitation is no longer white noise, but becomes colored. The harmonics are more excited than others frequencies. This can lead to failure of general OMA techniques [5].The failure can occur in three different ways. First of all it possible that the harmonics are identified as structural modes. However, in this case it should be possible to distinguish between harmonics and structural modes using some prior knowledge about the harmonic frequencies. A second failure mechanism occurs when the actual structural modes are close to the harmonic frequencies and the estimation of the structural modes is affected by the harmonic. Typically this will result in a poor damping estimate. Lastly, it is possible that the harmonics inhibit the identification of the structural modes. Examples of the different types of failure ar...

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Operational modal analysis in the presence of harmonic excitations by the use of transmissibility measurements

Cited by 102 publications

References 9 publications

The State-of-the-Art on Framework of Vibration-Based Structural Damage Identification for Decision Making

The State-of-the-Art on Framework of Vibration-Based Structural Damage Identification for Decision Making

A Novel method based on operational modal analysis for monitoring the preload degradation of linear guideways in machine tools

Operational Modal Analysis in the Presence of Harmonic Excitations: A Review

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