Research On Key Technologies For Flexible Visual Detection System Of Defects Inside Small Bores

Small bores and micro tubes are widely used in advanced manufacturing and production industry. Such as automobile engine manufacturing industry, aerospace industry, chemical industry and energy industry. The technology of measurement on the small bore’s interior features has important significance on manufacturing, quality controlling and safety security. The existing methods such as eddy-current, ultra sound and video endoscope, are often have the problem of low detection precision, needing couplants, needing much manual intervention, etc. And the methods above are difficult to measure the bores below 10 mm.This article presents a method that can achieve measurement on bores in any position and posture in working range. This article is based on an existing measurement system for small bores surface defects. The existing system have already achieved the diverting of exterior illumination and exporting of the interior image, and have preliminary implement the panoramic imaging of small bores and defect measurement. On the base of existing system, this paper introduced the industrial robot as the movement platform, greatly extended the working range of the system.The main work of this paper is:1.This paper introduces and analyzes the principle and the advantages, disadvantages of existing method of domestic and foreign, including the contact measurement method, non-contact measurement method(including optical method and non-optical method).2. This paper detailed introduced the system composition and working principle of the original system, the structure and optical sensing principle of core sensor component--the sight-pipe are analyzed. Several key aspects of image processing in original system is introduced, and several important parameters are analyzed. Based on the analysis of the original system, the limitations of the original system are put forward.3. Aiming at the problem of lackage of working range and flexibility in original system, the industrial robot is introduced as motion platform. The various parameters of the robot and the kinematics, inverse kinematics model is introduced. On the base of that, the system improvement plan is analyzed and a feasible solution is put forward. Also, the system work flow is given.4. The problem of alignment of sight-pipe and small bore is researched. The mathematical model of non-alignment is conducted and the quantitative relationship is given. Based on the point mining and fitting function of laser tracker, the coordinate system of measurement bore and sight-pipe is established. An alignment method is given and the posture adjustment mechanism is established.5.Because the error of alignment is existing, the final image would get distortion. This paper discusses this phenomenon, and the conclusion of distortion rate is given. And on the basis of the conclusion, a method of measurement distortion rate and correct the measuring results is put forward.6. For a well-built measurement system, this paper analyzes the factors that may affect the measurement accuracy, and the error synthesis is achieved. Then take a mass of experiments on small defects and correct the results of measurement with the aberration rate at the center of the defects. The results show that this method of distortion correction can improve the accuracy of the measurement.