中文摘要：

提出了通过视觉传感获取焊接过程中的焊接特征信息并利用神经网络模型预测焊缝背面宽度的方法。利用大功率盘形激光器焊接了低碳钢SS400焊件,在焊接过程中改变焊接功率、焊接速度和焊接路径,并利用两台高速摄像机同步获取焊件正面和侧面出现的焊接特征信息。对获取的图像进行色彩空间转换、分层、滤波去噪和空域图像处理,提取飞溅、熔池和金属蒸气等焊接特征信息,观察焊接路径对各个特征的影响。最后,建立了一个三层的LMBP（LevenbergMarquardt Back Propagation）神经网络模型,将提取的特征信息作为输入量,预测焊缝的背面宽度。结果显示：当熔透不稳定或出现未熔透状态时,LMBP神经网络拟合度大于0.83,最大训练误差均值为0.002 8mm,最大实际误差均值为0.225 6mm。试验结果表明所建立的预测模型具有良好的准确性和稳定性。

英文摘要：

A method was proposed to obtain characteristic information in a welding process by visual sensing and to predict the weld width of weldment bottom surface by using a neural network model.A workpiece made from mild steel SS400 was welded by a high power disk laser.In welding processing,the weld conditions were changed,including laser welding power,welding speed and welding route and two high speed cameras were used to capture images containing characteristic information on both top surface and side surface of weldment simultaneously.In order to get a better characteristics extraction,the colour space of a RGB image was changed into NTSC（National Television Standards Committee）colour space,then both RGB image and YIQ image were separated into their colour components,filtered to denoising and processed in space domain.The weld characteristic information was extracted,including spatter,weld pool and metal vapour and the effect of weld route on characteristic information was researched.Finally,a LMBP（Levenberg-Marquardt Back Propagation）neural network model including three layers and one hidden layer was established.The obtained characteristic information was taken as input,and the weld width of weldment bottom surface was predicted.The results show that when the welding penetration is unstable or lack of penetration,the fitting degree of LMBP neural network is greater than 0.83,the maximum training error mean is 0.002 8mm,and maximum actual error mean is 0.225 6mm.It concludes that the prediction model has good accuracy and stability.