Monitoring the Dynamics of a Helicopter Main Rotor With High-Speed Stereophotogrammetry

Lundstrom, Troy; Baqersad, Javad; Niezrecki, Christopher

doi:10.1111/ext.12127

Cited by 16 publications

(7 citation statements)

References 11 publications

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“…Three‐dimensional (3D) digital image correlation (DIC) and 3D point tracking (3DPT) systems have proven their efficiency in being able to perform noncontact inspections 29 . They provide accurate quantitative information of structural deformations, full‐field strain maps, geometry profiles, and modal parameters 30 over a wide range of civil and mechanical engineering systems such as rotating machinery, 31 bridges, 32 railroad tracks, 33 and composite materials 34 . In recent years, computer vision and stereophotogrammetry approaches have gained substantial popularity for WTB monitoring and dynamic behavior characterization because of their noncontact nature 35,36 .…”

Section: Introductionmentioning

confidence: 99%

Multicamera measurement system to evaluate the dynamic response of utility‐scale wind turbine blades

et al. 2020

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Wind turbine blade certification requires static and fatigue testing at a large-scale facility similar to the Wind Technology Testing Center (WTTC) located in Charlestown, Massachusetts. Usually, these tests are conducted by using wire-based sensors such as strain gages, accelerometers, and string potentiometers. These systems are expensive, require a time-consuming installation (e.g., up to 3 weeks and $35 k-$50 k for a strain gage system on a 55-m-long blade), are difficult to deploy on large-sized structures, require additional instrumentations (e.g., power amplifiers and data acquisition systems), and produce results only at a handful of a discrete number of measurement points. In this study, a multicamera measurement system is implemented and experimentally evaluated to obtain full-field displacement and strain over a~12-m-long portion of a~60-m utility-scale wind turbine blade. The proposed system has the potential to streamline the certification process by reducing the blade's preparation and sensor installation cost and time to a few hundreds of dollars (for painting equipment) and a few days for preparing the surface of the blade for the test. Furthermore, operational modal analysis was used in conjunction with the multicamera system to estimate the natural frequencies and mode shapes of the wind turbine blade. The obtained results have shown that the proposed approach can detect in-plane displacement as low as 0.2 mm, mechanical strain with an error below 3% when compared with measurement performed using strain gages, and the first five natural frequencies with an error below 2% when compared with data recorded using traditional wire-based accelerometers. This paper presents these results and provides a summary of the strengths and weaknesses of the proposed optical measurement approach in the context of streamlining the blade certification/testing process and performing vision-based structural dynamic measurements on large-scale structures. K E Y W O R D Sdigital image correlation, fatigue tests, operational modal analysis, stitched field of view, structural health monitoring, wind turbine blades

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Section: Introductionmentioning

confidence: 99%

Multicamera measurement system to evaluate the dynamic response of utility‐scale wind turbine blades

et al. 2020

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“…Their results showed that deformations could be measured within ±25 mm from 220 m away. Similar applications of this method have been reported for impact testing, as well as monitoring the main rotor of a helicopter in both grounded and hovering operation conditions .…”

Section: Introductionmentioning

confidence: 65%

Full‐field deformation measurements during seismic loading of masonry buildings

Rajaram

Vanniamparambil

Khan

et al. 2016

Struct. Control Health Monit.

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This article demonstrates the potential of the digital image correlation (DIC) method to provide accurate full-field deformation measurements and successfully monitor the development of damage during seismic excitation of a partially grouted reinforced masonry building. The building was subjected to a sequence of earthquake ground motion records using the Large High Performance Outdoor Shake Table at the University of California, San Diego. The DIC setup was capable of measuring surface deformations of the single-story building with high frame rate cameras located at a distance greater than 50 ft away. The accuracy of the measurements was assessed with data obtained using mounted displacement transducers. The full-field deformation data collected by the DIC system was capable to detect strain localization patterns associated with the onset of wall cracking before it could be shown by the displacement sensor data or by post mortem visual inspection. The research findings reported herein demonstrate, for the first time to the authors' best knowledge, the potential of in situ monitoring of actual structures for damage induced by non-stationary loading profiles using optical metrology.

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“…With the similar approach, Bernardini et al [12] assessed the structural and inertial properties of two main rotor blades designed for ultralight helicopters. Lundstrom et al [13] combined stereophotogrammetry and modal parameter identification to monitor the dynamics of a 10.1 m diameter helicopter rotor. Moreover, Dong et al [14] integrated a stereovision system with a grid-pattern pressure-sensitive paint system, based on which simultaneous displacement and pressure measurements of a rotor blade were performed.…”

Section: Introductionmentioning

confidence: 99%

Full-Field Displacement Measurements of Helicopter Rotor Blades Using Stereophotogrammetry

Zuo

Wei

et al. 2021

International Journal of Aerospace Engineering

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This study presents a stereophotogrammetry approach to achieve full-field displacement measurements of helicopter rotor blades. The method is demonstrated in the wind tunnel test of a 2 m diameter rotor, conducted at the 5.5 m × 4 m Aeroacoustic Wind Tunnel of China Aerodynamics Research and Development Center (CARDC). By arranging the retroreflective targets on the special hat installed directly above the rotor hub, the dynamic motion of the rotor shaft was tracked accurately, and a unified coordinate system was established on the rotor. Therefore, three-dimensional coordinates of instantaneously measured targets attached on the blade could be transformed to the unified rotor coordinate system, thereby providing a basis for consistently calculating the blade displacements at different test conditions. Moreover, location deviations of the blade caused by the vibration of the measuring system or the rotor due to freestream and rotor rotation were also effectively corrected through coordinate transformation. Comparisons of experimental and simulation results for a range of hover and forward flight conditions show good magnitude and trend agreements.

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Monitoring the Dynamics of a Helicopter Main Rotor With High-Speed Stereophotogrammetry

Cited by 16 publications

References 11 publications

Multicamera measurement system to evaluate the dynamic response of utility‐scale wind turbine blades

Multicamera measurement system to evaluate the dynamic response of utility‐scale wind turbine blades

Full‐field deformation measurements during seismic loading of masonry buildings

Full-Field Displacement Measurements of Helicopter Rotor Blades Using Stereophotogrammetry

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