Template-Free Nonrevisiting Uniform Coverage Path Planning on Curved Surfaces

A novel mechanism to generate nonrevisiting uniform coverage (NUC) paths on arbitrarily shaped object surfaces is presented in this work. Given a nonplanar surface, nonzero curvature makes traditional homeomorphic fitting of regular template coverage paths from planar regions onto the object surface non-distance-preserving. Any coverage path with a realistic tooling size derived in this way will suffer from overlaps and missing gaps when transformed onto the object surfaces, unable to uniformly cover the target. To overcome this, a discretization process is adopted to represent the object surface as a uniform unstructured mesh, with resolution set in accordance to the tool size. It is proven that a coverage skeleton path must exist by mesh subdivision refinement which, after a local optimization step to improve overlap, missing gaps, and smoothness, gives rise to template-free superior NUC paths. Extensive simulation examples are presented to prove the validity of the proposed strategy in realistic settings. The proposed scheme is able to achieve 95.9% coverage on benchmark surface tests, outperforming comparable coverage algorithms, such as a homeomorphic boustrophedon mapping, which can at best achieve 80.9% coverage, or more recent state-of-the-art methods able to reach 94.7% coverage. An accompanying video is supplied with examples, including a real-world implementation of an NUC path tracked by a manipulator. An open-source implementation has been made available.