Saddle-shaped Curve Automatic Welding Research And Development Of Numerical Control System

In the pipeline welding process of transportation for petroleum and natural gas, usually meet saddle welding seam which is shaped by vertical connected two pipes. The complicated curve is usually welded by handwork and semiautomatic welding machine because the low level of welding automation. According to weld status in our country, auto-welding control technology of saddle-shaped curve is investigated in depth and the auto-welding control system is developed based on the numerical control (NC) principle.With the analysis of the characteristics of auto-welding numerical control system (NCS) of saddle-shaped curve and the importance of its application, the way to control the weld process of saddle-shaped curve with modern NC technique is put forward. The basic structure, control parameters and welding process are studied for the development of NCS.The traditional interpolation algorithms are not applicable for saddle-shaped curve as it is very complex. Interpolation algorithms for saddle-shaped curve which is based on point by point comparison method and angle approaching is put forward after discussing the selection of interpolation algorithm and design regulation and researching the characteristics of saddle-shaped curve. In the thesis, interpolation algorithm based on angle approaching is decided to use in the NCS by analyzing the two algorithms. Besides the excellence of high interpolation precision, the algorithm has greatly simplified the design of programming system.Welding parameters are the key to affect weld quality and difficult to control. Based on the analysis of control requests, the saddle-shaped curve is cut into several nonuniform parts and put forward using interpolation algorithm of nonuniform cubic B-spline curve to control welding parameters. It solves the problem of changing the welding parameters real time and realizes the continuous change of welding parameters.A PC-based NCS for auto-welding of saddle-shaped curve is developed. First, the NCS is designed from openness and function by understanding the characteristics of saddled-shaped curve and welding requests. Second, the NCS is designed from hardware and software in detail. The NCS not only realize the auto-welding of saddle-shaped curve, manual regulation but also the automatic programming, graphic simulation and so on.