Dynamic nonlinear modeling of 3D weld pool surface in GTAW

As the weld pool contains abundant information about the welding process, the skilled welder always utilizes the observed information to control the weld pool to get a good weld quality. In this paper, a real-time vision sensing technology is used as the eyes of the welder to observe the gas tungsten arc welding (GTAW) pool surface and a 3D reconstruction technology is used to reconstruct the observed weld pool surface in three-dimensions. The geometric parameters are obtained from the reconstructed pool surface. Step responses are conducted to acquire the relationship between the weld pool geometric parameters and the random variation of current, and the time-domain analysis of the system is done. Various random experiments are also conducted and the dynamic relationship of the weld current and the weld pool geometric parameters is established by means of a non-linear Hammerstein model.     

Control of 3D weld pool surface

The 3D weld pool surface in gas tungsten arc welding (GTAW) is characterized by its width, length, convexity and measured in real-time using an innovative machine vision system. The dynamic response of these characteristic parameters to welding current and speed as control variables is modeled. Based on the identified dynamic model, a predictive control algorithm is developed to control these characteristic parameters. The proposed algorithm is given in a closed form and no online optimization is required. Welding experiments confirm that the developed control system is effective in achieving the desired 3D weld pool surface geometry despite various disturbances.     

SPR传感器阵列中微流通池的流场仿真

在自制表面等离子体激元共振(SPR)传感器阵列检测装置的微流通池的研制中,为了获得更好的检测精度和重复性,需要流经各检测点的流量尽可能一致。设计了几种不同的微流通池结构,并利用Comsol Multiphysics软件对其内部的流场进行仿真分析。首先,分析了常用梭状流通池的内部流场分布,并研究了不同长度过渡段对流场分布的影响。在此基础上,讨论了不同流通池形状,特别是流通池外形轮廓,如椭圆状流通池和边界流线型更好的流通池对流场分布的影响。此后,还研究了过渡区中微结构阵列设计对检测区流场分布的影响。仿真研究结果表明:适当延长过渡段长度,有利于改善流体流动的稳定性和均匀性,但这种改善将随长度的进一步增加逐渐减弱。而不同的边界外形轮廓对检测区域流场的影响不大;当采用一定的微结构阵列扰流设计后,流场均匀性一定程度上得到改善。