Impact-Pose Estimation Using ArUco Markers in Structural Dynamics

Abstract

In structural dynamics a structure’s dynamic properties are often determined from its frequency-response functions (FRFs). Commonly, FRFs are determined by measuring a structure’s response while it is subjected to controlled excitation. Impact excitation performed by hand is a popular way to perform this step, as it enables rapid FRF acquisition for each individual excitation location. On the other hand, the precise location of impacts performed by hand is difficult to estimate and relies mainly on the experimentalist’s skills. Furthermore, deviations in the impact’s location and direction affect the FRFs across the entire frequency range. This paper proposes the use of ArUco markers for an impact-pose estimation for the use in FRF acquisition campaign. The approach relies on two dodecahedrons with markers on each face, one mounted on the impact hammer and another at a known location on the structure. An experimental setup with an analog trigger is suggested, recording an image at the exact time of the impact. A camera with a fixed aperture is used to capture the images, from which the impact pose is estimated in the structure’s coordinate system. Finally, a procedure to compensate for the location error is presented. This relies on the linear dependency of the FRFs in relation to the impact offset.