Degree Name

Doctor of Philosophy


Faculty of Engineering


Robotic welding may be used to enhance quality and improve operating conditions in manufacturing and repair situations. However, it may be difficult to implement robot automation for some applications which involve non-repetitive tasks such as in repair and reclamation work. The present work was aimed to address some of the robotic automation difficulties that arise in such situations where it is necessary to rapidly generate a robot program for every different task, in particular for weld repair.

A technique for rapidly generating off-line robot programs for weld repair was developed in this work. The system proposed uses a single camera in order to obtain information about the object to be welded. To perform the task, it is not necessary to know the geometry of the system “a priori” although smoothness of the overall shape of the object is assumed. Artificial feature points are used with the aim of being able to obtain the characteristics of the shape of the object in 3 dimensions.

A software application was developed which provides the system with an easy to use interface, sequence control and data processing which in combination with a vision system and a tactile technique allows weld repair jobs to be performed on complex curved surfaces.

A review of two camera calibration techniques was carried out as well as a review of commercial devices and techniques used to map 3D surfaces. A modification to the planes camera calibration method was suggested and tested. Two methods to estimate 3D coordinates were review and tested, additionally a combination of these two methods was also tested. Results showing the errors obtained with the various combinations of camera calibration methods and 3D estimation methods were obtained. A technique to “unfold” a three dimensional surface (i.e. to create a two dimensional representation of a three imensional surface) was proposed and used as an essential part of the image data processing. Tests were performed to evaluate the system and encouraging results were obtained.

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