Development of 3D scan integrated robot arm control for pulse-echo laser ultrasonic testing

Abstract

Pulse-echo (PE) laser ultrasonic testing (LUT) is a reliable non-destructive testing (NDT) method used to inspect subsurface damages in composite materials. Accurate detection and localization of damages require a perpendicular impingement angle and a constant stand-off distance between the sensing laser and the inspection surface. A 6-degree-offreedom robot arm can carry the specimen along a raster path to maintain these requirements throughout the LUT process. However, the movement requires precise control over the position and orientation of the robot arm's tool center point (TCP), which depends on the shape of the inspection target. In real-world applications, mathematical representations or 3D CAD models of the inspection target are not always available. This study proposes the use of 3D scan-generated models to create raster scan paths for robotic PE LUT. Geometries of the region of interest (ROI) are utilized to generate the necessary scan grids for controlling the robot arm's movement.