Research On Nuclear Pipeline Maintenance-oriented Multi-agent Telerobotic Welding System

Welding technology is important and irreplaceable in national economicconstruction and social development. For nuclear radiation, undersea pressure, outerspace oxygen-poor and microgravity in extreme environment welding task such asmaintenance in nuclear power plants, marine engineering and pipeline maintenanceundersea, construction and maintenance space stations, it is necessary for operator toimplement remote welding at a safe place away from the worksite, monitor thewelding process and control the reomte welding equipment such as robot from adistance. The integration methods of telerobotic welding system have been studiedfor pipeline segment replacement strategy in nuclear pipeline maintenance. Thepipeline assembly and welding task was completed by multi-agent technology and theresearch work will be the foundation for further practical application of teleroboticwelding technology in nuclear pipeline maintenanve area.According to the features of pipeline serving at nuclear, pipeline segmentreplacement maintenance strategy was designed. The multi-agent robot system framewas set up based on telerobotic welding technology in existence. Using multi-agenttechnology, sub-systems of current telerobotic welding system have been packagedby their different features. They are compound agent, Response agent, deliberationagent, effects-based agent and goal-based agent. The agent interior database was setup. The agent communicated with each other by WinSock programming interface ofTCP/IP local area network protocol based on blackboard communication mechanism.The agents integration was collectivity designed for multi-agent system organizationand coordination. Cross-functional angets was organized to agents union forminglayering agents sturcture system. Agent utility in agents union was evaluated byunion strategy utility division algorithm.Based on multi-agent robot system frame, pipeline remote welding agent usingin small diameter pipeling all-position welding and general changing remote robotinterface were produced. Pipeling welding device was divided into mechanicaltransmission module, Pneumatic clamping module and welding torch moduleaccording modulization designing. General changing remote robot interface consistedby self-adaptive interface disk, master port connecting with robot, passive portconnecting with end-effector, electric coupler and air channel interface. The weldingarc length was stably controlled using well-behaved linear relationship between arcvoltage and arc length. The pipeline remote welding agent was packaged todeliberation agent and endowed with interior knowledge. Agent was connected by network and human-robot interface was designed.Central management agent was set up according coordination technology andremote welding features. As a software agent, central management agent provided anoperation, coordination and communication platform and a friendly human-robotinterface.Analysising the redundancy of multi-agent remote welding system, agentcoordination algorithm was came up with multi-agent competition mechanism basedon contract net technologe. Agent capability was evaluated by human-robot fuzzyevaluation algorithm. Agents experiences library stored agent execution efficiency,agent execution result and de-blurring operator comments. Testing module was builtup to record and monitor the multi-agent operation process. For convenient operation,testing module was embeded in central management agent and human-robot interfacewill record agents action. Testing module can be inserted to any agent because ofindependent design and be improved for different process and aim to simplify testingoperation.Task management agent was designed to break down welding operation process.Total task can be separated to several sub-task and every sub-task can becontinuously separated to sub-sub-task. And then, complex task was simplified.Agents resources assignment methods for total task, sub task and sub-sub taskcontained direct assignment, precatory assignment and bid-based assignment. Taskmanagement agent was packaged to deliberation agent and task managementagenthuman-robot union and interface were designed.Agent functions perfectibility was the foundation to ensuring agents systemnormal operation. In connection with pipeline remote welding agent, welding torchrotation concentricity experiment, welding torch adjusting experiment and welingtorch performance experiment were carried out. Experiments results show thatpipeline all-position welding device can get through the small diameter pipelineautomatic welding and meet the requirment of remote welding system.Agents union were set up according multi-agent remote operation strategy,which were PTP automatic remote operation union and master-slave manual remoteoperation union. The redundancy, competition anf coordination of agents union wasverified by experiment of welding tool joining with remote operation robot. Agentsunion operation effects were evaluated by execution efficiency, force and momentchanging. For pipeline assembling process, master hand redundancy coordinating ofmaster-slave remote operation was tested. Experiments results show that centralmanagement agent can record agent operation results and agents experiences librarywill stored quantitative testing results and operator experiences.Pipeline maintenance welding experiments were completed by multi-agent telerobotic welding system, which were joining operation between pipeline remotewelding agent and remote robot agent, assembling operation between pipeline remotewelding agent and pipeline, welding pipeline, disassembling of pipeline remotewelding agent. Experiments results show that the telerobtic welding systemintegration is feasible by using multi-agent technology and nuclear pipeline remotewelding can be realized by this system.