Determination of three-dimensional movement for rotary blades using digital image correlation

• A modified NR algorithm was proposed which was useful in case of large rotation.
• A synchronized stereo high-speed camera system was established.
• This technique could be potentially applied to on-line monitoring the work condition of the wind turbine.

Non-contact and accurate motion measurement of the rotary objects is crucial in engineering applications. A modified Newton–Raphson algorithm, which is capable of positioning marks with large rotation, has been proposed. A stereo imaging system with a pair of synchronized digital high-speed cameras was developed and achieved full-field displacement measurement based on 3D image correlation photogrammetry for rotary objects. This system has been applied to measuring the 3D motion of a wind turbine blade model. The displacement components of the rotary blade were presented, and the corresponding frequency spectra were investigated. The experimental results demonstrated that the proposed system could measure the 3D motion of rotary blades precisely, and it also provided an alternative potential non-contact diagnosis means for large wind turbine blades.