A Novel Robotic System for Finishing of Freeform Surfaces

Surface finishing of freeform surfaces is predominately a manual operation that requires a considerable amount of operator skill; automation of this process has many benefits, including consistent surface quality, preventing hazardous exposure to particulate, etc. A novel robotic surface finishing system, consisting of a robot and an end-effector that includes a force sensor, finishing tool, and proximity laser sensor, is developed in this paper to automate the surface finishing process. The laser sensor is treated as an additional link, and based on it a novel perception system is developed for real-time scanning of the surface that provides the surface profile mesh and the corresponding normal vectors which can be used directly by the robot closed-loop control system for pose tracking. A unique feature of the perception system is that the geometry of the surface profile and normal vectors are all obtained in real-time in the robot base coordinate system, thus eliminating issues such as precise registration of the work piece in the fixture and its location with respect to the robot base coordinates. An impedance-type closed-loop control algorithm is developed for pose tracking. The proposed system and control algorithm are employed to conduct surface finishing experiments on wooden surfaces. A representative sample of the results and measurement images of surface finish are provided to illustrate the capabilities of the robotic surface finishing system. A video of the system in operation is also provided.