Design and validation of a sensor guided control system for robot welding in shipbuilding

New areas in welding large structures in shipbuilding include joining large sections such as double-hull constructions. Joining these sections create great problems for a manual welder since welding takes place in a closed area with associated work environmental problems. The accessibility to the working area is limited to a manhole and the use of robots for welding such structures requires new robot design that are adapted for the task as well as the additional requirements of one-off production. This paper will describe research work and results within the ROWER-2 project. The aim of the project was to design a robot system for joining ship sections in the final stage when ship sections are to be assembled together in dry dock. Due to a high degree of manual work involved in the assembly procedure of the ship, the project addressed both productivity and quality issues. An important part within the project was to develop control algorithms for seam tracking during welding based on through-arc sensing. The aim was to be able to cope with tolerances in the joints after manual setup and tack welding of the structure. A special software system, FUSE, was developed for this purpose that seamlessly integrates commercial available software tools such as Matlab and Envision (robot simulator). Simulation in FUSE showed that the major part of the development of sensor guided robot control algorithms should be performed by simulation, since it cuts time, expenses and efforts, especially when software simulation is included in the methodology.

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