Continuous Offset-Based Coverage Paths for Planar Regions

May 11, 2022 · 2 min read
projects

Undergraduate research project, 2022

Key ideas explored

  • A geometric distinction between local and global self-intersections in contour-parallel offset curves, and how they affect coverage continuity.
  • Use of medial-axis width structure to reason about when offsetting causes a region to split, and how modifying width can prevent topological disconnection.
  • A simple pre-processing technique that converts a family of offset loops into a single spiral-like continuous path.
  • Identification of sharp-turn regions induced by offsetting and localized smoothing without globally altering equidistance.

Local vs. Global Self-intersections
GSI-elimination
spiral curve generation example

Limitations and scope

  • This work does not claim empirical superiority over existing infill or coverage strategies used in modern additive manufacturing.
  • The approach prioritizes geometric continuity over material optimality, and is most relevant to contexts where uniform coverage and motion smoothness dominate.
  • The algorithms are primarily geometric and exploratory; no large-scale benchmarking or hardware validation was performed.

In hindsight, this project shaped how I think about the relationship between geometric structure, modeling assumptions, and real-world relevance. Many of the limitations of this work informed my later focus on formally scoped, validated methods in safe learning and control.


Follow-up: Corner Smoothing for Additive Manufacturing Toolpaths (May 2021 — Aug 2021)

As a natural extension of the coverage-path work above, I later proposed a corner-smoothing method for additive manufacturing toolpaths, aiming to achieve uniform coating while constraining maximum curvature. I refined the original formulation into a convex optimization problem enforcing continuous curvature and even area coverage, implemented an iterative gradient-based solver in Python, and integrated it into the parallel-curve toolpath planner from the coverage-path project.

Research Assistant (May 2021 — Aug 2021)

  • Proposed a corner smoothing method for additive manufacturing toolpaths to achieve uniform coating while constraining maximum curvature.
  • Refined the original formulation into a convex optimization problem to enforce continuous curvature and even area coverage.
  • Implemented an iterative solver (gradient-based) in Python and integrated it into a parallel-curve toolpath planner.

Tech: Convex optimization, Python.

Shengfan Cao
Authors
PhD Researcher in Autonomous Driving & Robotics
UC Berkeley Ph.D. candidate developing safe, machine-learning-based prediction, planning, and control systems for autonomous vehicles. First-author IEEE IROS oral presenter with 4+ years across machine learning, planning, and controls, spanning PyTorch research, CARLA evaluation, embedded-robot deployment, and C++ production planner integration.