Strategy of calculating minimal-distance of engine pipelines based on point cloud data

A strategy of calculating minimal-distance of engine pipelines based on point data was proposed to inspect whether the minimal-distance meets the design requirement. The strategy includes five steps: (1) the points belonging to the same pipeline was picked up and saved in a group. (2) A set of equal-interval grid was built along a coordinate direction in which the pipeline stretched longest. Then the point cloud data were divided into corresponding grid according to the coordinates. The center point of each grid was calculated and the trend-line data of pipeline were constituted. (3) On each trend-line point, a projection plane was built vertically to a straight line connecting the point and its adjacent point. Then point cloud data of pipeline were projected to the nearest projection plane. And a group of projected points in arc distribution were obtained on each projection plane. (4) The projected points on each projection plane were fitted into a circle using least square fitting method. And the center points of all circles constituted the center-line points of a pipeline. And the mean radius of each fitted circle was regarded as pipeline radius. (5) Traversing method was used to calculate minimal-distance between two groups of center-line points. And minimal-distance of two pipeline surfaces was calculated by subtracting radii of two pipelines from the minimal-distance of center-line points. Four groups of pipelines were examined to verify the proposed strategy. The results showed that the deviations of minimal-distance of two pipeline surfaces were within -0.35~0.46mm. And the deviations of pipeline radius were within -0.08~0.22mm. The proposed method is more robust than mostly used method and also meaningful for realizing digital inspection of pipeline distance.