Structural Evaluation of a Utility-Scale Wind Turbine Blade Using a Multi-Camera 3D DIC
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Transcript of Structural Evaluation of a Utility-Scale Wind Turbine Blade Using a Multi-Camera 3D DIC
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Peyman Poozesh, Christopher NiezreckiWind Technology Testing Center (WTTC)
July 11, 2016
Multi-Camera 3D DIC
Structural Evaluation of a Utility-Scale Wind Turbine Blade
Using a Multi-Camera 3D DIC
Static Fatigue
Structural Dynamics and Acoustic Systems LaboratoryUniversity of Massachusetts Lowell
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Problem Statement
One hindrance to the rapid evolution of new wind turbine blade designs is wind
turbine testing and certification process
Static Test
Fatigue Test
A typical 50m utility-scale blade requires:
‒ ~200 strain gages costing $35k-$50k
‒ ~20 high sensitivity accelerometers costing $12K-$30k
‒ Takes 3 weeks to setup the blade for the
test
Transducers are able to measure at discrete locations.
Prior knowledge of high strain and maximum displacement
areas is needed.
Photo by Dennis Schroeder | NREL
(b)
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A single pair of DIC cameras may not be able to measure the
whole utility scale wind turbine blade.
Adjusting the distance between the cameras and object reduce the
accuracy.
The complex curvature of the test structure may produce visual
blind spots that cannot be covered by a conventional stereo
camera pair.
Blade monitoring system – Based on Stereo-photogrammetry:
Solution And Approach
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Solution And Approach
Multi-camera 3D Digital Image Correlation (3D DIC) system:
– Composed of several conventional stereo DIC systems.
– System considers any two cameras as a stereovision system.
– Each stereo vision system can measure a limited area of the object.
– The resulted displacement fields are stitched together to form global
point clouds.
Master Stereo DIC Slave Stereo DIC
CCD1
CCD2
CCD3
CCD4
Integrated DIC System
G
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Proposed Methodology – Multi-Camera System
Measurement - Multi-Camera System
Output-Only System Identification
The performance of
system identification
methods in the presence of
noise is unknown
Modal
Parameters
( )
3D Digital
Image
Correlation
3D Point
Tracking
Method
Full-field
Strain and
displacement
Phase I
Phase II
Output-only
system
identification
Attainment
of full-field
3D displacement,
strain and modal
parameters of
a utility scale
blade
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Phase II – Optically-Based Modal Test
A multi-camera measurement system is used to estimate modal
parameters of a utility scale wind turbine blade.
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Project Synopsis
Attainment of full-
field displacement,
strain, and modal
parameters on utility-scale blades
Accuracy of 3D DIC in
measuring large areas
may be too high
Different stitching
approaches induce
varying errors that are not
yet quantified
The physical constraints
associated with WTTC will be identified
The accuracy using a single
stereo-vision system will be determined
Conduct an experiment on a
large area to identify measurement error
Evaluate different dynamic
stitching methods (PCA,
SVD, and ICP) on a lab-
scale blade
The robustness of each of the techniques will be resolved
Analytically and experimentally
evaluate the sensitivity of system ID on modal parameter estimation
Accurate prediction of damping
Understanding the effectiveness of system ID considering noise
Scaled mode shapes
Improving the accuracy of estimated modal parameters
Use an initial displacement to scale
frequency response function and
select optimal excitation to excite all the modes
Measurement - Multi-Camera 3D DIC
Output-Only System Identification
Problem
Solution
Outcome
The performance of
system identification
methods in the presence of
noise is unknown
Mode shapes extracted
from OMA is un-scaled
and vibration modes may
not be well excited