A Measurement Method for Large Parts Combining with Feature Compression Extraction and Directed Edge-Point Criterion

Abstract

High-accuracy surface measurement of large aviation parts is a significant guarantee of aircraft assembly with high quality. The result of boundary measurement is a significant parameter for aviation-part measurement. This paper proposes a measurement method for accurately measuring the surface and boundary of aviation part with feature compression extraction and directed edge-point criterion. To improve the measurement accuracy of both the surface and boundary of large parts, extraction method of global boundary and feature analysis of local stripe are combined. The center feature of laser stripe is obtained with high accuracy and less calculation using a sub-pixel centroid extraction method based on compress processing. This method consists of a compressing process of images and judgment criterion of laser stripe centers. An edge-point extraction method based on directed arc-length criterion is proposed to obtain accurate boundary. Finally, a high-precision reconstruction of aerospace part is achieved. Experiments are performed both in a laboratory and an industrial field. The physical measurements validate that the mean distance deviation of the proposed method is 0.47 mm. The results of the field experimentation show the validity of the proposed method.

A 3D measurement method with accurate boundaries based on mutation feature detection of laser stripes

“…However, the profile of a part, particularly its boundary information, is neglected when preserving some data with a certain distance or is measured with low accuracy. We have presented a laser scanning measurement method and completed a field measurement for an aviation composite part [20]. However, the accurate 3D boundary of the part is dif ficult to obtain.…”

“…In this paper, a binocular vision measurement method based on an auxiliary laser is used to measure large parts [20]. In order to simplify the interference of redundant information in the image, a scanning laser stripe, being the unique feature, is constructed to enhance the part's features in images.…”

Global Measurement Method for Large-Scale Components Based on a Multiple Field of View Combination

“…Second, the surface of the large-scale component is artificially divided into several parts and separately measured by the binocular cameras at different positions; based on binocular vision method with assisted laser, the 3D point cloud data of measured part is obtained [21]. Third, feature points on the transfer mark are measured by two theodolites for coordinate system transformation.…”

“…The assisted laser stripes that are projected on the surface of the component are captured by a binocular vision measurement system. Prior to reconstructing the laser stripes, the centres of the stripes are extracted using a grey centroid method [21]. The corresponding centre points of the left and right images are matched by the polar constraint of the cameras of the binocular vision system.…”