等离子体加工技术在处理各类难加工材料的成形与制备方面备受关注,其温度特性是影响加工质量的决定性因素.针对现有温度特性研究大多在弧径向对称的假设前提下间隔采样测量完成的问题,提出了一种基于灰度值的非对称等离子体弧形貌三维重建方法.首先,基于自行设计的图像采集系统,给出了CCD空间布置方案,同步获取了360.方向上加工过程中的等离子体弧数字图像；然后,对采集图像进行了灰度化、直方图均衡化、滤波去噪以及灰度等值线提取等预处理,以获得良好的视觉场和测量效果；最后,取内六层灰度等值线进行了基于立体匹配和插值重构的数值模拟,建立了与温度场存在相关性的等离子体弧形貌三维模型.研究结果定性地描述了等离子体弧温度场的分布情况,实现了等离子体弧形貌的非接触测量,得到了加工过程中等离子体弧的真实形貌.%Plasma processing technology has been concerned in the forming and preparation of various difficult machining materials. He 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.
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