Segmentation and Coverage Planning of Freeform Geometries for Robotic Surface Finishing

Surface finishing such as grinding or polishing is a time-consuming task, involves health risks for humans and is still largely performed by hand. Due to the high curvatures of complex geometries, different areas of the surface cannot be optimally reached by a simple strategy using a tool with a relatively large and flat finishing disk. In this paper, a planning method is presented that uses a variable contact point on the finishing disk as an additional degree of freedom. Different strategies for covering the workpiece surface are used to optimize the surface finishing process and ensure the coverage of concave areas. Therefore, an automatic segmentation method is developed to find areas with a uniform machining strategy based on the exact tool and workpiece geometry. Further, a method for planning coverage paths is presented, in which the contact area is modeled to realize an adaptive spacing between path lines. The approach was evaluated in simulation and practical experiments on the DLR SARA robot. The results show high coverage for complex freeform geometry and that adaptive spacing can optimize the overall process by reducing uncovered gaps and overlaps between coverage lines.