Iterference Detection Technique For Aircraft Components Assembly

To the interference problems of aircraft components assembly, the paper proposes a interference detection scheme about practical assembly. In the first, scan the assembly parts using the laser scanning to acquire scanning data. Through the scanning data handling and analysis, the key features are extracted and the interference conditions are calculated. The follow-up assembly handling is guided by the key features or interference conditions.The technique and theory about template customizing are stated. The template is basis of the paper and customized according to CAD model. The template is used to help to extract the features and simplify the interference detection. The template is including two types: edge feature template and assembly part template.A technology based on statistical features is proposed to matching point cloud models, i.e. through making corresponding statistical features of free model and fixed model be coinciding to finish matching. The statistical features based matching is include two circumstances: complete matching and incomplete matching. If statistical features can constrain six degrees of freedom of free model, free model and fixed model can be matching completely. If the number of constrained degrees of freedom is less than six, incomplete matching is finished and follow-up handling is required to finish model matching. The follow-up handling is as follows: interactively adjust unconstrained degrees of freedom to acquire the matching of vision of free model and fixed model, and then accurately match them using ICP algorithm. Both two matching schemes are stable and reliable, and global optimal solution is acquired.A method based on template is proposed to extract the edges of point cloud. The template is customized according to CAD model, and it includes discrete points and their corresponding tangent vectors on the theoretical edges. After the template and point cloud are matched, point cloud is sliced by some planes to acquire sectional data. Every plane of these planes is constructed by one theoretical edge point and its corresponding tangent vector. Segment every sectional data into two parts according to the theoretical edge point, and fit the two parts into two curves. The intersection point or tangent point of the two curves is the point on the practical edges. Through curves fitting and section optimization, the practical edge points existing in point cloud can be positioned and the ones not existing in point cloud can be acquired by interpolating, so the extracting precision of edges is guaranteed. The extraction technique of 2D symmetry edge is proposed and deeply researched.A template based interference detection technology is proposed. The template is customized according to CAD model of assembly part. Match the template with scanning data, and the template after being matched is the reconstruction model. One of two assembly parts mating each other is converted into layered parallel sectional profiles by slicing technique, and the sectional profiles are perpendicular to assembling direction. Calculate the interference conditions of every section and all of them constitute the interference conditions of three-dimension objects. The method simplifies the 3D intersection to 2D, and not only the permeation depth and clearance but also the interference distribution is given.To solve the interference problem during aircraft components assembly, a quantitativly guiding sheme is proposed which is including repairing, filling piece and re-ajusting pose. The sheme offers suggested value including repairing value, filling piece thickness and pose deviation to guide the components assembly.In the end, some advanced topics in the proposed methodology that needs further investigation in future are presented and addressed.