中文摘要：

为保障等离子体设备安全运行，推动等离子体在材料加工领域的实际应用，指导等离子体发生器系统设计及优化运行，通过分析采集到的可见光图像与放电电压信号，提出了一种对双射流直流电弧等离子体的放电稳定性进行诊断的方法。基于双射流等离子体实验平台，采集随固定时间变化的可见光图像和放电电压；针对可见光图像，引入图像处理领域的8方向Freeman链码分析技术，从时域和频域2个方面定义了周长、面积、相关系数、幅度谱4个定量指标，并结合放电电压对等离子体电弧-射流区形状特征和稳定性进行定量分析。结果表明：周长和面积确定了电弧-射流区边界的几何尺寸，相关系数描述了电弧-射流区边界的形状差异，幅度谱分布则很好地反映了电弧-射流区边界形状的平滑性。

英文摘要：

In order to ensure the safe operation of plasma equipment, to promote the application of plasma in material processing, and to guide the design and optimization of plasma generation systems, we proposed a method for diagnosing the discharge stability of dual-jet DC arc plasmas through collecting and analyzing the visible images and the discharge voltage of dual-jet DC arc plasmas. The visible images and the discharging voltage were recorded simultaneously at a preset time interval on a dual-jet plasma experimental platform. By introducing the eight-direction Freeman chain codes for image procession, we defined four parameters including perimeter, area, correlation coefficient in time domain, and the FFT amplitude in frequency domain. Using these four parameters and the discharge voltage, we quantitatively ana- lyzed the discharge stability in the plasma arc-jet region. The results show that the perimeter and the area determine the geometrical sizes of the arc-jet boundaries, the correlation coefficient describes the boundary differences, and the FFT amplitude reflects the boundary smoothness of the arc-jet region.