High-accuracy 3-D deformation measurement method with an improved structured-light principle

In this paper, a high-accuracy 3-D deformation measurement (HADM) method with structured light is proposed and applied to wing deformation measurement in wind tunnel experiments. The present method employs an arbitrarily arranged fringe projector and a perpendicularly placed camera. The exact phase-height mapping using the phase differences of the projected sinusoidal fringe patterns, as well as the spatial distribution of the fringe, is accurately derived. It not only presents high feasibility but also reduces systemic uncertainties arising from deviations between the ideal model and the real-world conditions. Meanwhile, a dynamic boundary process algorithm is proposed to reduce the measurement uncertainty caused by fringe fracture near the object boundary. It is calibrated that a high accuracy with the average measurement uncertainty of 0.0237 mm is achieved, which is less than 0.01% of the side length of 25 cm of the field of view. In the wind tunnel experiments, the 3-D deformations of the elastic wing, particularly the key geometric parameters such as wing tip position, angle of attack, and dihedral angle, are well reconstructed to provide an in-depth explanation for the aerodynamic characteristics.