Study On Virtual Reality Monitoring Technology Applied In Robot Welding Repair Of Shield Machine Cutter Head

Shield machine is a kind of large engineering machinery specially used for excavation,soil transportation and tunnel support,and it is applied more and more frequently in China.As the most important part of a shield machine,cutter head has a significant bearing on the project schedule.However,it is usually worn out by friction with rock and soil under complicated and unexpected working conditions,sometimes,it may even cause project delays.As a result,cutter head repair technology is very important.In general,hyperbaric repair is used because of its high efficiency and little harm to project environment.However,toxic gases generated and potential collapses make this technique dangerous for human beings.So replacing welders with robot is the best solution for repairing under high pressures.In the study,virtual reality technology and remotely controlled robot are creatively integrated in cutter head hyperbaric repair.In this way,welders could operate robot by virtual reality technology in the safe control room,as if they did it on welding field.It is carried out in the following ways:1.On the basis of analyzing shield machine structure and hyperbaric repair methods of cutter head,the author proposes a robot repair system.It consists of three parts: virtual reality monitoring system in the safe control room,a robot to carry out welding in the operation site,and other equipment to connect them in the transition chamber,such as robot control unit and welding power source.2.A virtual reality monitoring system testing platform is built to simulate shield machine cutter head repair process.The testing platform is made up of several units: a six-joint industrial robot and a digital welding power source for welding,a two-axis positioner to simulate horizontal welding and vertical welding position,an arc welding analyzer and data acquisition card to collect information of voltage and current,as well as cameras to record the welding porcedure.The system can be used to simulate welding procedure of cutter head repair.3.Communication between virtual reality monitoring program and remotely controlled robot system is accomplished by using C++ and TCP/IP protocol in a client server mode.According to features of the virtual reality monitoring program,the author writes and tests network communication codes,so that it can transfer data accurately and timely.4.A three-dimensional model of virtual environment and the robot is built in virtual reality monitoring program in 1:1 scale,so that it can give operators a reliable viewing reference.Besides,the author creates the virtual scene,including models at different levels,lights,and bounding boxes for collision detection.5.A virtual reality monitoring program is developed in C# language based on Unity.By communicating with remotely controlled robot system,the virtual robot can synchronize with the real one,detect collisions and send feedbacks of robot operation in a graphical user interface.So,operators can monitor and control the robot by using the system.6.Data acquisition program is implemented in C++ language based on Qt.The program can collect information of welding current and voltage,plot wave curves,as well as record and save information of welding.7.The author conducts a test to simulate shield machine cutter head repair based on virtual reality monitoring program.He adopts gas metal arc welding process to weld Q345 steel plate,and stimulates horizontal welding position and vertical welding position typically used in cutter hear repair.The test shows that the virtual reality monitoring program has functions such as synchronization,collision detection,welding parameters sampling and good telepresence shown to operators.With the help of the virtual reality monitoring system and camera viewing,operators not only can carry out robot teaching remotely,but also can observe the welding process accurately,comprehensively and flexibly.A conclusion can be made from the test that,it is feasible to apply the virtual reality monitoring system in robot welding repair of shield machine cutter head.