Wire plus arc additive manufacturing (WAAM) has been demonstrated to be a powerful technique to produce large-scale metal parts with low cost. However, techniques to achieve accurate geometry control and high process stability have not yet been perfectly developed. Although implementing vision sensing and closed-loop control can contribute to promoting the levels of process automation and stability, it is difficult to markedly improve the geometry precision of parts by only performing the current layer detection due to a large detection lag with vision-based sensors. To deal with this issue, this study proposes a novel strategy of introducing the previous layer information into the current deposition height to increase the response speed of the control system. The previous and current layer heights are monitored by a passive vision sensor. The height features are extracted by image processing algorithms mainly including edge detection, threshold division, and line fitting. Deviations in deposition height are automatically compensated via controlling the wire feed speed based on a PID controller. A helpful software interface is implemented in the Visual C++ environment to study the automatic detection and control system. In comparison to the closed-loop control using only the current layer detection, the deposition height of thin-walled parts can be excellently controlled by the proposed control system using the visual inspection of previous and current layers, significantly increasing the process stability and achieving accurate height control in WAAM.

线加电弧增材制造（WAAM）已被证明是一种低成本生产大型金属零件的强大技术。然而，尚未实现精确实现几何形状控制和高工艺稳定性的技术。尽管实施视觉感测和闭环控制可有助于提高过程自动化和稳定性，但是由于基于视觉的传感器检测延迟较大，仅通过执行当前层检测很难显着提高零件的几何精度。为了解决这个问题，本研究提出了一种新颖的策略，将先前的层信息引入当前的沉积高度，以提高控制系统的响应速度。先前和当前层的高度由被动视觉传感器监控。通过图像处理算法提取高度特征，这些算法主要包括边缘检测，阈值划分和线条拟合。通过基于PID控制器控制焊丝进给速度，可以自动补偿沉积高度的偏差。在Visual C ++环境中实现了有用的软件界面，以研究自动检测和控制系统。与仅使用当前层检测的闭环控制相比，薄型零件的沉积高度可以通过所提出的控制系统通过对先前和当前层的目视检查来极好地控制，从而显着提高了工艺稳定性并实现了精确测量。 WAAM中的高度控制。通过基于PID控制器控制焊丝进给速度，可以自动补偿沉积高度的偏差。在Visual C ++环境中实现了有用的软件界面，以研究自动检测和控制系统。与仅使用当前层检测的闭环控制相比，薄型零件的沉积高度可以通过所提出的控制系统对先前层和当前层进行目测来很好地控制，从而显着提高了工艺稳定性并实现了精确测量。 WAAM中的高度控制。通过基于PID控制器控制焊丝进给速度，可以自动补偿沉积高度的偏差。在Visual C ++环境中实现了有用的软件界面，以研究自动检测和控制系统。与仅使用当前层检测的闭环控制相比，薄型零件的沉积高度可以通过所提出的控制系统通过对先前和当前层的目视检查来极好地控制，从而显着提高了工艺稳定性并实现了精确测量。 WAAM中的高度控制。