关键词: 基准检测, 机器视觉, 存在概率, 自动化装配, 边缘检测, 装配基准

Abstract:

Regarding the disturbance problem of automatic assembly system reference hole detection due to such factors like aviation sealant and tack fasteners， this paper analyzes the characteristics of assembly reference hole in industrial environment and the limitations of current detection algorithm， and proposes a robust detection method of multi-type assembly reference hole based on monocular vision. This method selects the optimal arc based on the bow-string ratio and chord length. By analyzing the associated convexity between the optimal arc and residual arcs， the rapid filtering of arc segments is realized. An improved circle detection algorithm based on the probability of existence map is proposed to fit the approximate circles of assembly reference hole. The accurate clustering of arc segments is achieved by the set distance threshold and the approximate circle of assembly reference hole. Finally， ellipse fitting is performed by using direct least-squares method. And the false alarms are subsequently removed. Through field testing and accuracy verification， the algorithm has a significant inhibitory effect on the common disturbance factors in the assembly scene. The detection accuracy （aperture） and positioning accuracy （hole spacing） of the reference hole are 0.10 mm and 0.09 mm respectively. The average recall rates of the algorithm for the detection of multi-type assembly reference hole of rivets， target points， through-holes and holes with piercing clamps are 97.9%， 98.3%， 99.1% and 91.1% respectively， which can meet the detection requirements of automatic assembly system.

Key words: reference detection, machine vision, existence probability, automatic assembly, edge detection, assembly reference