Development and application of an intelligent welding robot system for shipbuilding

Over the last few decades, there have been a large number of attempts to automate welding in the shipbuilding process. However, there are still many non-automated welding operations in the double-hulled blocks, even though it presents an extremely hazardous environment for the workers. And, the hazards come about mainly because of the dimensional constraints of the access-hole. Thus, much effort has been recently directed toward the research on compact design of the fully-autonomous robot working inside of the double-hulled structures. This paper describes the design, integration, simulations, and field testing trials of a new type of welding robotic system, the RRXC, which is composed of a 6-axis modularized controller, a 3P3R serial manipulator, and an auxiliary transportation device. The entire cross section of the RRXC is small enough to be placed inside the double-hulled structures via a conventional access hole of 500×700 mm2, from the outside shipyard floor. The weight of the manufactured RRXC is 60 kg, with a 6-axis manipulator and modularized controller, and the weight of an auxiliary transportation device is 8 kg, with a 2.5 m steel wire of 6Φ. Throughout the field tests in the enclosed structures of shipbuilding, the developed RRXC has successfully demonstrated welding functions without the use of any additional finishing by manual welders, and has shown good mobility using an auxiliary transportation device in double-hulled structures.