Design and modeling of pipeline welding robot based on Pieper criterion and construction of integrated intelligent welding system

The welding efficiency and weld formation quality of pipeline external welding are important factors that constrain the site laying speed and service performance of long-distance oil and gas pipeline. It is urgent to optimize the structure and function of pipeline welding equipment and control system, and improve the intelligent level of the external welding process. This paper focuses on improving weld bead formation quality during the pipeline all-position welding. Based on the Pieper criterion, a 5-degree of freedom (DOF) welding robot is designed. It can meet the control requirements of welding torch position and posture (WTPP) that comply with the welding process parameters at any welding position of pipeline. The kinematic model of the designed robot is established, and an analytical solution to its inverse kinematics is derived. Combined with the composite sensor based on combined laser line structured lights vision sensor and gravity sensor, the pipeline all-position intelligent welding system is integrally constructed. Based on this, the detection method of welding groove size and WTPP parameters is proposed. Through the designed program control strategy, the intelligent adjustment experiments of the WTPP were carried out during the pipeline all-position welding process. The lateral tracking deviation of welding torch was not more than 0.25 mm; the vertical tracking deviation was not more than 0.63 mm, and the posture angles feedback control deviation were not more than 0.8°. The good weld formation effect was obtained, which provides support for the improvement of the intelligent level of pipeline external welding.