Output-Only Modal Analysis Using Continuous-Scan Laser Doppler Vibrometry and Application to a 20kW Wind Turbine

Laser vibrometry is a powerful tool for measurement of vibration on a variety of structures. Lasers do not mass-load or otherwise change the dynamics of a structure, and so they have enabled measurements from surfaces that are too light, delicate, hot, etc. to allow conventional surface mounted sensors. The position of the measurement point can also be changed readily. Thus, laser vibrometry has also allowed acquisition of measurements over a dense grid of points, to more completely characterize a structure its deformation shapes, the evolution of stress waves, or the identification of structural damages than it might be feasible with other methods. The chapter is divided in two sections: the first one is intended to provide an insight about the theory behind laser Doppler vibrometry (LDV), while the second section aims at giving an overview of the different types of laser Doppler vibrometers that have been developed so far. The chapter is not intended to give a comprehensive discussion of laser Doppler vibrometry, but it provides sufficient details about potentials, issues, and best practice approaches for successfully exploiting such technique in structural dynamics testing. References are provided to direct the interested reader to more detailed information as well as to examples of application cases.

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“…A schematic of the CSLDV process is shown in Fig. 16, as well as a photograph from an actual CSLDV test from [38].…”

Section: Special Solutionsmentioning

confidence: 99%

Laser Doppler Vibrometry Measurements in Structural Dynamics

Chiariotti¹,

Rembe²,

Castellini³

et al. 2020

Handbook of Experimental Structural Dynamics

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“…Other studies using CSLDV to attempt to overcome this were inconclusive as the wind turbine was in parked position. A wind turbine requires wind speeds greater than the cut‐in wind speed of 3.5 m/s for at least 10 minutes before it releases the parking brake and starts to generate electricity, not in actual operating mode.…”

Section: State Of the Art In Classical Contact And Noncontact Sensorsmentioning

confidence: 99%

A review of ground‐based radar as a noncontact sensor for structural health monitoring of in‐field wind turbines blades

et al. 2018

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Ground‐based radar (GBR) are increasingly being used either as a vibration‐based or as guided‐wave‐based structural health monitoring (SHM) sensors for monitoring of wind turbines blades. Despite various studies mentioning the use of radar as transducer for SHM, a singular exclusive review of GBR in blade monitoring may have been lacking. Various studies undertaken for SHM of blades using GBR have largely been laboratory‐based or with actual wind turbines in parked positions or focussed on the extraction of only specific condition parameters like frequency or deflection with no validation with actual expected operating data. The present study provides quantitative data that relates in‐field monitoring of wind turbines by GBR with actual design operating data. As such it helps the monitoring of blades during design, testing, and operation. Further, it supports the determination of fatigue damage for in‐field wind turbine blades especially those made of composite materials by way of condition parameters residuals and deflection. A review of the two GBR–SHM approaches is thus undertaken. Additionally, a case study demonstrating its practical use as a vibration‐based noncontact SHM sensors is also provided. The study contributes to the monitoring of blades during design, testing, and operation. Further, it supports the determination of damage detection for in‐field wind turbine blades within a 3‐tier SHM framework especially those made of composite materials by way of condition parameter residuals of extracted modal frequencies and deflection.

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“…Laser vibrometry has been used to inspect turbine blades for damage in many studies [50][51][52] . The focus of these studies however has been to investigate modal responses of healthy and damaged blades.…”

Section: Laser Vibrometry Damage Detection Studiesmentioning

confidence: 99%

Damage detection in a composite wind turbine blade using 3D scanning laser vibrometry

Marks

Gillam

Clarke

et al. 2016

Proceedings of the Institution of Mechanical Engineers, Part C:

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As worldwide wind energy generation capacity grows, there is an increasing demand to ensure structural integrity of the turbine blades to maintain efficient and safe energy generation. Currently, traditional non-destructive testing methods and visual inspections are employed which require the turbine to be out-of-operation during the inspection periods, resulting in costly and lengthy downtime. This study experimentally investigates the potential for using Lamb waves to monitor the structural integrity of a composite wind turbine blade that has been subject to an impact representative of damage which occurs in service. 3D scanning laser vibrometry was used to measure Lamb waves excited at three different frequencies both prior to, and after, impact to identify settings for an optimal system. Signal processing techniques were applied to the datasets to successfully locate the damage and highlight regions on the structure where the Lamb wave was significantly influenced by the presence of the impact damage. Damage size resulting from the impact was found to correlate well with the laser vibrometry results. The study concluded that acousto-ultrasonic-based structural health monitoring systems have great potential for monitoring the structural integrity of wind turbine blades.

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Output-Only Modal Analysis Using Continuous-Scan Laser Doppler Vibrometry and Application to a 20kW Wind Turbine

Cited by 16 publications

References 20 publications

Laser Doppler Vibrometry Measurements in Structural Dynamics

Laser Doppler Vibrometry Measurements in Structural Dynamics

A review of ground‐based radar as a noncontact sensor for structural health monitoring of in‐field wind turbines blades

Damage detection in a composite wind turbine blade using 3D scanning laser vibrometry

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