Feasibility-Oriented Region-Based Optimization of Functional Redundancy in Robotic Surface Finishing

Robotic surface finishing of free-form workpieces requires kinematically feasible robot motion over the complete workpiece surface. For an axisymmetric finishing tool, rotation about the tool axis is functionally redundant and can in principle vary continuously along a prescribed machining trajectory. This work instead considers a region-based representation in which one fixed optimized redundancy angle is assigned to each machining region, allowing robot feasibility to be established at the surface level before the final machining paths are generated. In the first stage, the workpiece placement and regional redundancy angles are jointly optimized to achieve complete feasible coverage of the sampled surface targets under prescribed kinematic constraints while maximizing the global minimum constrained singular value. In the second stage, machining directions are determined while the optimized workpiece placement, regional subdivision, and redundancy angles remain fixed, after which the final surface-following toolpaths are generated. The method was evaluated on two workpieces of different geometric complexity and validated on a KUKA KR 10 R1440-2 industrial robot. The results demonstrated improved limiting task-constrained kinematic capability and successful execution of the optimized robot trajectories. The framework also reduced the need for manual trial-and-error in selecting workpiece placement and regional redundancy angles. Overall, the method provides a systematic planning strategy for achieving feasible surface coverage while preserving inverse-kinematic continuity.