Global DIC algorithm for vibrating and rotating object tracking

Digital Image Correlation (DIC) is a widely used non-contact method for full-field displacement measurement under static and dynamic conditions. However, conventional algorithms struggle with large rotations, typically limited to 10-15, making them unsuitable for rotating objects like wheels, turbines, or gears. Current workarounds involve using databases of static images at various angles to find a suitable reference image, but this approach lacks flexibility. This research presents a global DIC algorithm capable of tracking rotating objects without relying on image databases. A grid of points is defined on the reference image and numerically rotated around a specified center. Bicubic spline interpolation is used to estimate grey levels at non-integer positions in the deformed image. These are compared with reference values to compute an error, minimized through an optimization process based on a Gauss-Newton scheme. The method was validated on experimental images of a rotating PC fan, showing effective tracking for angles up to 90.