On-Machine Detection Of Grouped Guide Holes On Aircraft Structure Parts Based On Machine Vision

As the most common structure in aircraft parts,guide hole is mainly used to connect various aircraft parts.The machining error of guide hole has great influence on the structural safety and service life of the aircraft.In the traditional manufacturing process of aircraft,China's aircraft manufacturing factory mainly used simple and extensive measurements to inspect machining error of guide hole,such as open-eye inspection and plug gauges.Under the new digital assembly technology system of aircraft,the NC machining technology of hole is applied to aircraft structural parts with complex shapes,and the traditional measurements cannot meet the fast,efficient,digital and high-precision inspection requirements.In this paper,an on-machine inspection system based on machine vision is designed and implemented for grouped guide holes on aircraft structural parts.The main research contents include:1.The inspection technology of grouped guide holes which use one image to inspect multiple guide holes at the same time was proposed and implemented,and it is also called multiple holes inspection technology.Multiple holes inspection technology is an on-machine vision inspection technology which integrated machine vision inspection technology into five-axis numerical control technology.The onmachine inspection method used in this paper made up for the deficiency in limited field of single visual inspection technology,with non-contact,good flexibility,fast and accurate characteristics.2.Reasonable detection path is the key to achieve high efficiency inspection.This paper discussed the inspection path planning problem in the multi-hole inspection technology,and designed and implemented the inspection path planning algorithm of grouped holes.3.This paper studied the calibration method of camera parameters based on five-axis CNC machine tool and the calibration method of the relationship between camera and machine spindle,and designed and implemented a rapid calibration technology for system parameters.4.This paper discussed how to use the path planning information and system calibration information to generate NC codes correspond to a specific machine type,which is used to grab inspection images by camera.And an automatic image acquisition and transmission technology based on network port communication was designed and implemented in the paper.5.This paper studied the three-dimensional machining error evaluation technology of grouped guide holes based on non-orthographic image in the multi-hole detection technology.The evaluation technique includes two parts: the inspection image processing and the machining error evaluation.Using the characteristics of inspection image,an accurate,reliable and robust edge extraction algorithm based on local image segmentation was proposed.In the part of machining error evaluation,a threedimensional machining error evaluation model of grouped guide holes was established in this paper.By using the processing result of inspection image and the theoretic information of guide hole,the actual three-dimensional machining information of guide hole can be obtained.After comparing with the theoretic information of guide hole,the evaluation results of three-dimensional machining error of grouped guide hole in parts coordinate system can be obtained.Based on the overall technical scheme and research on key techniques,the author developed the hardware of inspection system,and developed system software based on Visual Studio 2013 platform.Finally,several experiments verified the feasibility of the multiple holes inspection technology and the inspection accuracy of the on-machine inspection system.The developed system has been applied to the actual inspection for guide hole by some aviation manufacturer.