Three-dimensional reconstruction for non-symmetric plasma arc appearance based on gray value

ZHENG Qingyu, LIU Xin, SUN Jing, KONG Hongling
(School of Mechanical Engineering, Dalian University of Technology, Dalian 116024, China)

Abstract: Plasma processing technology has been concerned in the forming and preparation of various difficult machining materials. The temperature of the plasma arc is the decisive factor of influencing processing quality. The most existing studies on temperature characteristic are completed by interval sampling measurement under the assumptions of arc radial symmetry. In order to solve this problem, a threedimensional reconstruction method for nonsymmetric plasma arc appearance based on gray value was presented. First of all, based on the selfdeveloped image acquisition system, the space layout of CCD was given and the digital images of processing plasma arc in the direction of 360°were acquired synchronously. Then image preprocessing such as gray processing, histogram equalization, filtering denoising and gray contours extraction were implemented on the digital images in order to get good visual field and measuring effect. Finally, after numerical simulation based on stereo matching and interpolation through six gray contours from inner to outer of the plasma arc, a threedimensional model of the plasma arc appearance which has correlation with temperature field was established. The results describe the distribution of the plasma arc temperature field qualitatively, achieve the noncontact measurement of the plasma arc appearance and get the real appearance of the processing plasma arc.
Key words:  threedimensional reconstruction; nonsymmetric plasma arc;noncontact measurement; gray value;  CCD image acquisition