Deformable shape registration using surface-based free-form deformations in robotic welding

In this paper, a novel approach is presented to perform a deformable shape registration of workpiece geometries in robotic welding. Based on the free-form deformation (FFD) method, a surface-based extension FFDS is presented where the initial shape of the control points lattice corresponds to the shape of the surface to be deformed. A point-based registration is performed using the sum of least squares criteria to obtain the non-rigid shape transformation. The deformation is applied to the computer-aided design (CAD) model of the workpiece geometry preserving its topology for subsequent robot path planning to move a welding gun along the deformed part contours. The performance of the presented approach is evaluated using virtual test data and rea measurements of a welding workpiece obtained with a 3D sensor. Moreover, the performance of this approach is compared to state of the art deformable shape registration revealing a significant reduction of computation time and the usability for path planning in robotic welding.