The Research Of Contact-tip-workpiece-distance Control In Narrow Groove Piprline Based On Arc Sensor

With the continuous exploitation of land oil and gas resources, the production of a large number of oil field has been declining. People focus their eyes on the rich marine oil and gas. The security and efficient transportation mode of ocean oil and gas resource is pipeline transportation. The stable and efficient welding of pipeline can reduce the cost of sub-sea pipeline laying and the labor intensity of workers. During the sub-sea pipeline laying process, welding process is not stable because of the assemble error of groove group and the thermal deformation error and the installation error of welding orbit. To guarantee the good welding effect, the welding torch needs real-time adjustment in the height and cross direction achieving the seaming tracking.The essay is based on the national natural science funds: the arc sensing technology research projects of sub-sea pipeline laying narrow groove welding robot. The arc sensing seam tracking system was set up based on CAN bus. The high-frequency oscillation welding platform based on CAN bus was designed to realize the motion frequency of 40 HZ. The mathematical model of arc sensor was established. The effect rules of different filter parameters on the arc sensor were studied in the CTWD tracking experiments. The experimental results show that the moving average filter slide points were 100 and the median filtering area of the window was 5 gained better filtering effects. The extracting method of deviation signal in the process of seam tracking was studied and the mathematical model between the welding current and welding torch height under different welding specification was built. The common used methods of CTWD seam tracking were studied and the set point of welding current was obtained in CTWD seam tracking under the different welding specification. The multiple model controller based on fuzzy switching rules was proposed in the CTWD seam tracking of the pipeline all position welding.The arc sensitivity of oscillation frequency was studied on the high frequency oscillating platform. The experimental results show that the welding torch swing frequency at about 10 HZ can get the good deviation signal. The effect of welding current by the different groove shape such as 30° V groove, 60° V groove and J form narrow groove was analyzed. The actual welding current is not much difference between the 30° V groove and the 60° V groove and the set point of welding current can use the same value. The average welding current of 30 ° V groove and 60 ° V increases 20 A than that of J form narrow groove. The effect of different welding location to welding current was analyzed. The process of the welding current will first increase and then decreased from 0° to 180° location during the welding process. In the welding torch height of linear increase experiments, welding torch height increased from 9 mm to 18 mm and the first-order linear relationship between torch height and the welding current was fitting out. The all-position welding parameters of large diameter UOE sub-sea pipeline were studied and the qualities of welding bead meet the API 1104-2005 standard. The arc sensing seam tracking program based on the Lab VIEW was written. The seam tracking effect was good and could meet the needs of pipeline welding.The signal processing methods, deviation signal extraction methods and control methods in the all-position welding process of CTWD tracking were studied in this thesis. The influence law of different groove form on the welding current was analyzed and the all-position pipeline welding parameters were obtained. Through the above method, the good CTWD tracking effect guarantees the high-efficiency sub-sea pipeline laying and the welding quality. The research results provide technical reserves to the pipeline laying industry. It has the great scientific significance and engineering application prospects.