建立BP神经网络拟合曲面，实现激光焊接数据的预测(BP neural network mainly through 4 steps in the implementation of MATLAB, read file setting parameters, create a BP network, neural network training, neural network simulation. After the program, some basic parameters are set up. The operation of the program can get the neural network structure. It includes training algorithm, training progress, iteration number, maximum mean square error, response time and error variation curve.)