Enhancing surface following with invariant differential part models

This paper deals with the combination of model-based programming and sensor-based execution of surface following tasks. It shows how differential workpiece models, in combinations with proper matching strategies, allow a robust and high quality (i.e. fast and accurate) task execution in the presence of positioning and modelling inaccuracies. A geometric description of the local shape of curves and surfaces in the neighbourhood of the current “contact-point” is given in terms of local curvature and torsion, as used in differential geometry. Matching strategies try to find a good correspondence between the real contact point on the physical workpiece and its counterpart in the model. For this purpose, local characteristics of the surface are derived from sensor and control signals. Experiments show how the introduction of heuristic rules can make the application of model information less sensitive to matching errors