Abstract
In non-destructive testing (NDT) of metal welds, weld line tracking is usually performed outdoors, where the structured light sources are always disturbed by various noises, such as sunlight, shadows, and reflections from the weld line surface. In this paper, we design a cross structured light (CSL) to detect the weld line and propose a robust laser stripe segmentation algorithm to overcome the noises in structured light images. An adaptive monochromatic space is applied to preprocess the image with ambient noises. In the monochromatic image, the laser stripe obtained is recovered as a multichannel signal by minimum entropy deconvolution. Lastly, the stripe centre points are extracted from the image. In experiments, the CSL sensor and the proposed algorithm are applied to guide a wall climbing robot inspecting the weld line of a wind power tower. The experimental results show that the CSL sensor can capture the 3D information of the welds with high accuracy, and the proposed algorithm contributes to the weld line inspection and the robot navigation.
Highlights
non-destructive testing (NDT) is very important to guarantee the safe operation of lots of industry facilities, such as wind turbine towers and oil storage tanks
Unlike weld seam detection in a welding process, weld line tracking for NDT is usually performed outdoors; the sensor is challenged by noise and illumination intensity variations
This paper proposes a structured light sensor with cross stripes and a segmentation algorithm of the stripe for vision navigation of a wall climbing robot in outdoor environments
Summary
NDT is very important to guarantee the safe operation of lots of industry facilities, such as wind turbine towers and oil storage tanks In these industrial situations, automatic weld line tracking can navigate moving wall climbing robots and improve the testing performance significantly. From the perspective of sensors, structured light is a typical vision sensor, which possesses the merits of simplicity, noncontact, strong anti-interference abilities and others It has been widely used in many fields, such as robot navigation [1], automatic welding [2], industry inspection [3,4], 3D measurement [5,6,7] and quality control [8,9]. Unlike weld seam detection in a welding process, weld line tracking for NDT is usually performed outdoors; the sensor is challenged by noise and illumination intensity variations.
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