Inspection And 3-D Reconstruction For Inner Surface Of Small Diameter Pipes

Small-diameter pipes are widely used in many fields, such as aerospace, nuclear industry and so on. The quality of the inner surface has a great effect on the transport performance of the pipe. Therefore, these pipes should be inspected periodically. And the defective pipe should be repaired or replaced in order to avoiding the accident and decreasing the cost. Many methods have been already developed for measuring pipes whose inner diameters are larger than 20mm, but few adapt to the small-diameter pipes, especially the reconstruction of their inner surfaces. In this dissertation, a photoelectric inspection and three-dimensional reconstruction method is presented based on the characteristics of CCD and PSD. The inspection system can detect the inner surface of a small-diameter pipe which has an inner diameter of 9.5 mm～10.5 mm and a curvature radius of more than 100 mm. The measurement accuracy of this inspection system for the inner diameter and surface defect reaches to ±0.1 mm. Seven chapters are included in this dissertation.In chapter 1, the application background of the small-diameter pipes inspection technique is elaborated. And, the research present, characteristics and development trend are analyzed firstly. Then, some photoelectric inspection techniques and common devices including charge coupled device (CCD) and position sensitive device (PSD) are introduced. Based on that, a new inspection method is presented for the small-diameter pipes. Finally, the significance of the research and the main contents of this dissertation are summarized.In chapter 2, the measurement principle of CCD based inspection sensor is expounded in the beginning. A calculating model for the inner surface of small-diameter pipes is put forward based on the calibration of CCD camera. And the relative CCD inspection sensor is developed. The distortion parameters of CCD camera are obtained by the calibration. According to the characteristics of pipe inner section image, the relative image process and defect inspection program is competed. Some relative experiments are done in this chapter.In chapter 3, a non-contact sensor based on the principle of optical triangulation has been developed for inspecting and measuring the inner surface of long small-diameter pipes. An optical model of the PSD inspection sensor is set up. Some structure factors, which can affect the measurement error, are analyzed. And a...