| Cylinder has a large-scale application in machinery, energy, military and other fields. But in the process of cylinder production, traditional off-line methods of detection is using. To improve the speed of cylinder detection, cylinder on-line detection methods and systems are urgently needed to achieve at the factory. However, for the cylinder has one end closed and the temperature at the production scene is very high, the real-time on-line detection can't be achieved with the existing testing methods and machine vision systems. A vision-based one end closed cylinder wall geometric parameters on-line measurement method is presented in this paper, an imaging agency with special structure is designed, by processing the spot image which is formed by the laser reflector and reflects the cylinder wall geometry change, cylinder wall geometric parameters change information is accessed.The principle of machine vision is adopted, to test the inner wall of the cylinder. The method proposed in this paper is based on the laser triangulation method, with a new imaging method designed. Reflector is used to change the light path of the laser in this detection method, to make laser beam to the cylindrical surface of the inner wall, a spot image which reflects cylinder wall geometry changes formed, prism is used to imaging the laser spot on the image. The vertical in of laser and vertical out of image can be realized by this method. On the one hand, the method can detect cylinder wall perfectly, even the detection to the wall near the cylinder closed distal end can be achieved. The other hand, required electronic imaging equipment is setup away from the measured cylinder, the requirements which is need for long time working in the high temperature production environment is met.According to the new cylinder detection method, the cylinder detection system is designed. The system consists of imaging systems, which includes laser, mirror and prism, image acquisition system, which includes the lens, cameras and image acquisition card, and the mechanical system. The composition the optical reflector system is analyzed in detail, eventually a half pentagonal prism is taken to be the imaging devices. In this paper, the relationship between the camera and the lens is analyzed in detail, various parameters including the angle of view, field of view and working distance in accordance with the actual requirements is carefully calculated. According to the computation standard PAL camera which can reach 768×576 resolution when working with image acquisition card is selected, camera angle is need to be less than 7.84°. The mechanical devices has been designed and produced to the fixed laser, mirror, prism and cameras, with the position and angle of the mirror and prism adjustable. Demonstration model prototype which can achieve real-time on-line cylinder detection is made by assembling all components and mechanical devices.Laser spot positioning algorithm is studied in this paper, and program which can automatically change the spot images collected by the detection system to spot location data is designed. After the experiments of demonstration prototype model, it is showed that the resolution of the detection system of the inner wall can be 0.1 mm/pixel, wall size change detection range is not less than 30mm, and the detection time of one spot is less than 40ms. |
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