Automatic inspection of complex geometry welds for 5th International Conference on Advanced Robotics

Inspection of sub-sea welds requires the accurate placement of nondestructive examination (NDE) probes on the weld, in particular the weld roots. To achieve this the general form of the weld must be mapped and the roots identified. This paper describes the development of a manipulator based automatic weld inspection system designed specifically for dealing with the large, complex geometry, multipass welds which are typically found on off-shore structures. The system is operated under supervisory control. There are four stages to inspecting an underwater weld; location of the weld area, cleaning the weld area, precise location of the weld run and application of the NDE probe. It is the third of these which is addressed here. A laser generated structured light source is used to profile the weld, the image being detected by a CCD camera. Subsequent image processing identifies the roots and enables the general weld shape to be mapped in three-dimensional space. The entire assembly is mounted on the end of a PUMA 560 manipulator. The manipulator is guided around the weld by the information received from the weld mapping and the general trajectory of the weld estimated from the initial weld area location. To improve accuracy and minimise the effects of attenuation and back scatter it is necessary to approach the weld as closely as possible. This requires careful trajectory control making use of all available data, updating as appropriate, checking for possible collisions and avoiding arm singularities.<>