Study On Offshore Pipeline Laying Welding Robot System

All-position welding robot which is used to submarine pipeline laying isthe important special equipment of deep-water pipeline laying system. Theproductivity and reliability are most essential features of thesubmarine pipeline laying robot. Because submarine pipeline laying weldingrobot has been monopolized by foreign professional companies, the equipmentis not only expensive, but also its maintenance and welding process cost isexpensive, above all, our country don't have the ability to design andmanufacture the submarine pipeline laying welding robot, so these seriouslyhamper the exploration and development of South Sea oil and gas fields. Inorder to meet the needs of develop deep-water oil and gas fields, to break themonopoly of foreign technology and to achieve the localization of submarinepipeline laying welding robot, we must furtherly study the mechanical design,control system architecture, key technology and welding process of submarinepipeline laying welding robot.Based on the domestic and foreign research situation of pipelinewelding robot and the process characteristic of submarine pipeline layingall-position welding, the architecture of submarine pipeline laying welding system was analyzed, the whole design scheme and key technology ofsubmarine pipeline laying welding robot system were proposed. Themain research work follows:1. The open system structure of submarine pipeline welding robot controlsystem has been studied. The real-time control network data exchange modelbased on EtherCAT and real-time transverse interconnection fieldbus isestablished. Soft PLC process data mapping technology based on Windows isused to achieve data exchange of heterogeneous system and cooperationcontrol between functional subsystems. On the theoretical basis of opencontrol network architecture, the overall structure of the submarine pipelinelaying welding robot control system and functional subsystems are designed.Digital welding power based on CAN-open, motion control, angle sensing,electricity and gas auxiliary unit, a complete data management and on-linemonitoring functional unit is integrated in control system. Opening controlsystem is characterized by strong data processing and expandable ability,which can be extended to a number of intelligent applications, such as arcsensor, contact sensor, laser tracking.2. For the BLDCM which has a trapezoidal back-EMF,this dissertationproposes a novel id=0vector control method,it can effectively minimize thetorque ripple caused by distortion of the back-EMF and improve the precisionof motor control. Using double closed loops PID controller with velocity andcurrent, low-pass filters, and notch filters. The high frequency interferences in system were suppressed by low-pass filter, the machinery vibration atresonance point in pulling and rotating mechanism are attenuated by digitalnotch filter, so improving the control accuracy of the oscillation mechanism.The accuracy of oscillation width mainly depends on the gear gap measuredby laser displacement sensor and compensation.3. In allusion to the strict demand of synchronization of dual motordriving the running mechanism, the profile velocity operating mode using forvector group based on CAN-open protocol is presented, a novel protocolmodel named "communication by time-sharing and executing onsynchronization" was adopted for simultaneous executing velocity command.Due to a load imbalance problem and the discordance of two-axis actualvelocity caused by the coupling relationships between two drive motor byrigid joint, The master-slave speed follower arithmetic of dual-motor drivenwelding robot is proposed under the various loads. Experimentation resultindicates that the accuracy of two-axle synchronous movement and theoperation stability of welding robot are ensured by using the algorithm.4. Analysis of module's interface features of key equipment based onCAN-open communication, CAN-open device model principle and dataexchange process of the master-slave unit have been studied. By means ofSDO communication way to deploy equipmental Objects Dictionary, PDOcommunication is used to achieve process data fast exchange and cooperationcontrol between functional subsystems. 5. The welding operation mode that submarine pipeline laying productionlines has high welding quality and efficiency has been studied. According toproduction technology of assembly line, a multi-level control networkplatform is constructed to realize effective distribution control and cooperativemanagement for the whole assembly line. The technical means that dual-robotare cooperatively controlled to achieve the automatic weld bead overlayfunction in a welding workstations has been studied. The thesis achieves thedata exchange between the dual-robot control system by means of automationequipment specification communications technology and real-time Ethernettechnology, it also reads the shared variability by the dual-robot collaborativecontrol strategy, guarantees the position consistence between arc and stoppingthe arc, and makes the welding joints no defects.6. In allusion to the characteristics of pipeline welding process, technicaldifficulties achieving arc sensor in pipe welding were analyzed, high speedoscillation torch which is suitable for pipe welding was developed and be usedto study arc sensor in a higher oscillating frequency. The welding test platformwas built to preliminarily evaluate the sensitivity of arc sensor system. Thecurrent average of the border algorithm has been proposed to extract thelateral deviation of welding bead. The result showed that the trackingalgorithm is feasible, it's lay the foundation for furtherly study pipe weldingbased on arc sensor.7. The welding parameters matching rule of submarine pipeline laying welding robot was studied. A set of welding parameters adjustmentspecification has been obtained. These technological means which containsdual-torch welding procedure, narrow gap groove, an internal line-up clampwith copper was used in pipe welding test. With the welding proceduredeveloped in the welding laboratory, a series of sound welds have beenobtained efficiently in offshore pipeline laying welding site at Bohai Sea.These research results would provide the references for submarinepipeline laying welding robot design and manufacturing, and also lays thefoundation of further studies on intelligent key technologies. The content ofthis dissertation will effectively promote the process of practical engineeringapplications for submarine pipeline laying welding robot.