在分析TIG焊接弧光谱的基础上，设计出复合滤光镜头，与普通CCD摄像机组成视觉传感器，从试件正面观测熔池图像。焊接过程中根据电流大小通过软件调整采集图像亮度，得到了比较清晰的TIG焊接熔池图像。利用自行开发的图像处理算法。检测出了熔池正面的形状参数。该算法处理一幅图像像用时不超过70ms，满足实时检测的需要。

A real-time monitoring system is developed for detecting abnormal conditions in robotic gas metal arc welding. The butt-joint test pieces with cut gap are used to intentionally introduce the step disturbance of welding conditions. During the welding process, the welding voltage and current signals are sampled and processed on-line to extract the characteristic information reflecting the process quality. After 1st statistical processing, it is found that seven statistical parameters (the mean, standard deviation, variance, and kurtosis of welding voltage; the mean, variance, and kurtosis of welding current) show variations during the step disturbance. Through 2nd statistical processing of the means of the welding voltage for subgroups of continuous measurement, the statistical control chart is obtained, and SPC (statistical process control) -based on-line identifying method is developed. Ten robotic welding experiments are conducted to verify the real-time monitoring system. It is found that the correct identification rate for normal and abnormal welding conditions are 100% and 95%, respectively.

Establishing the correlation between transient behaviors of surface deformation of weld pools and workpiece penetration information, and quantitatively analyzing the surface deformation at top and bottom surfaces at the moment when the pool is penetrated and their dynamic responses to welding process parameters will provide many basic data for the realization of topside vision-based penetration control in gas tungsten arc welding (GTAW). A transient numerical model is developed to investigate the dynamic behaviors of full-penetrated GTAW weld pools in this paper. A whole and comprehensive scheme is used in which many factors such as moving arc, 3-D fluid and heat flow fields, transient state, full-penetrated weld pool and surface deformation at both top and bottom surfaces are considered. The transient developments of 3-D surface deformation and shape of weld pool during the period from partial penetration to full penetration are predicted. The simulated results show that the curves of ratios of the maximum depression to the length and width at top surface of weld pool at different times clearly indicate the basic information of penetration. So the relation of the ratios versus time can be used as an indicator to judge whether the weld pool is penetrated.

Achieving an effective utilization and exploitation of TIG welding arcs require a thorough understanding of the plasma properties and its physical processes. Through simultaneous solutions of the set of conservation equations for mass, momentum. Energy and current. a mathematical model has been developed to predict the velocity, temperature, and current density distributions in argon welding arcs. The predicted temperature fields in arc regions, and the distribution of current density and heat flux at the anode agree well with measurements reported in literatures. This work could lay the foundation for developing a comprehensive model of the TIG welding process wheve a dynamic, two-way coupling between the welding arc and the weld pool surface is properly represented.

The profile of the free surface deformation of a weld pool gives information about the extent of penetration depth, and weld bead apperance. Calculating the surface deformation of the weld pool is of great significance to the task of welding process modeling and simulation. Two nonlinear partial differential equations for describing both front- and back-side deformation of weld pool surfaces are derived in detail to make the physical terms and the sign of Lagrange multiplier in two equations be with one accord. Under some practical welding conditions, the secant method is used to determine the value of Lagrange multiplier, and the coupled equations are numerically solved to calculate both front and back free surfaces’ deformation of full-penetrated three-dimensional weld pools. The influence of the welding current on the surface depression of weld pool is examined. It shows that the predicted weld pool deformation is in agreement with the measurements