A research on quality monitoring system of spot welds with numerical simulator

本研究项目是关于开发一种在焊接过程中和焊接后不能直接观察而不进行破坏性试验的高速电阻点焊质量监测系统。这个想法是从一个概念推导出来的，即不可见的焊接状态(焊缝尺寸、温度场等)。如果像焊接现象这样的非线性现象可以用一些数学方程来描述，那么在计算机内存上制作的虚拟焊机中通过数值模拟器可以间接估计。对输入参数进行了焊接电流和焊接电压两种波形的测量，为模拟器提供了输入数据。在第一年，一些要在个人计算机上运行的计算机软件已经被开发出来，作为数字模拟器的工具。第二年，即1997年，开发了高速版本的模拟器，实现了适用于电阻点焊机的实时质量监测系统。然后，将安装了高速版本的个人计算机系统连接到电阻点焊机上，以检查该系统的可能性。1998年底，对焊缝尺寸估算系统的性能进行了评估，并给出了一些破坏性试验结果。在此基础上，提出了一种安装数值模拟器作为实时质量监控系统的新系统，并从该系统将通过网络与其他多个焊接和控制系统连接的角度进行了评估。结果表明，基于现象学建模的模拟器的改进算法实现了实时质量监控系统，提高了安装在PC机上的新CPU的计算速度。此外，本项目的下一个目标是利用高速质量监控技术实现焊接质量的实时控制系统。

This research project is regarding to a developing high-speed quality monitoring system for resistance spot welds that cannot be observed directly during and after welding without destructive tests. The idea has been deduced from a concept that the invisible welding state (weld size, temperature fields etc.) would be indirectly estimated in a virtual welding machine made on computer memory by a numerical simulator if the non-linear phenomena like the welding phenomena could be described with some mathematical equations. Two wave forms of welding current and welding voltage have been measured for the input parameters to make input data for the simulator.The research project had been started in 1996. In the first year, some computer software to be run on a personal computer had been developed as implements for the numerical simulator. In the second year, 1997, high speed version of the simulator was developed to realize a real-time quality monitoring system that can be applied for resistance spot welding machines. And then, a personal computer system installed the high speed version was connected to a resistance spot welding machine in order to examine the possibility of the system. In the last year of 1998, the system performance to estimate the weld size has been evaluated with some destructive test results. Furthermore, a new total system installed the numerical simulator as the real-time quality monitoring system has been proposed, and assessed from point of view that the system will connect to other many welding and control systems trough the network lines.As a result, it is clarified that the real-time quality monitoring system has be realized with a improved algorism for the simulator based on the phenomenological modeling, and increasing the computing speed of new CPUs mounted in the personal computers.In addition, next target of the project is to realize a real-time control system of the weld quality with the high speed quality monitoring technique.