In this research study, a novel optical measurement technique has been developed which can, in great detail, capture the displacement, velocity and acceleration of a rigid body. One example is an impactor in free fall striking a test specimen. Another application where the technique has succesfully been applied is during bird strike experiments. The technique sets itself apart by its ease of use and sub-pixel accuracy and precision. To achieve this, a 2D grayscale line pattern with known and constant pitch is applied to the rigid body. The grid pattern is filmed with a high speed camera perpendicular to its surface. The images, or rather the recorded intensities, undergo a Fourier transform and the phase shift of each subsequent frame is converted to a displacement measurement. Several operations are applied to optimally prepare the signal for a DTFT algorithm. Differentiating the signal to velocity and again to acceleration, which has also been measured with an accelerometer, proves the adequacy of the method. No calibration of the system is necessary, unlike with DIG, apart from an accurate measurement of the pitch.
展开▼
