High-Resolution Structure-from-Motion for Quantitative Measurement of Leading-Edge Roughness

Over time, erosion of the leading edge of wind turbine blades increases the leading-edge roughness (LER). This may reduce the aerodynamic performance of the blade and hence the annual energy production of the wind turbine. As early detection is key for cost-effective maintenance, inspection methods...

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Bibliographic Details
Published in:Energies (Basel) 2020-08, Vol.13 (15), p.3916
Main Authors: Nielsen, Mikkel Schou, Nikolov, Ivan, Kruse, Emil Krog, Garnæs, Jørgen, Madsen, Claus Brøndgaard
Format: Article
Language:English
Subjects:
Accuracy
blade inspection
Cameras
Confocal microscopy
Downtime
High resolution
Image acquisition
Inspection
leading-edge roughness
Microscopy
Outdoors
photogrammetry
quantitative 3D reconstruction
Spatial discrimination
Spatial resolution
structure from motion
Studies
surface analysis
Surface roughness
Topography
Turbine blades
Turbines
Unmanned aerial vehicles
Wind erosion
Wind power
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Summary:Over time, erosion of the leading edge of wind turbine blades increases the leading-edge roughness (LER). This may reduce the aerodynamic performance of the blade and hence the annual energy production of the wind turbine. As early detection is key for cost-effective maintenance, inspection methods are needed to quantify the LER of the blade. The aim of this proof-of-principle study is to determine whether high-resolution Structure-from-Motion (SfM) has the sufficient resolution and accuracy for quantitative inspection of LER. SfM provides 3D reconstruction of an object geometry using overlapping images of the object acquired with an RGB camera. Using information of the camera positions and orientations, absolute scale of the reconstruction can be achieved. Combined with a UAV platform, SfM has the potential for remote blade inspections with a reduced downtime. The tip of a decommissioned blade with an artificially enhanced erosion was used for the measurements. For validation, replica molding was used to transfer areas-of-interest to the lab for reference measurements using confocal microscopy. The SfM reconstruction resulted in a spatial resolution of 1 mm as well as a sub-mm accuracy in both the RMS surface roughness and the size of topographic features. In conclusion, high-resolution SfM demonstrated a successful quantitative reconstruction of LER.
ISSN:1996-1073
1996-1073
DOI:10.3390/en13153916