THAMP-3D: Tangent-Based Hybrid A* Motion Planning for Tethered Robots in Sloped 3D Terrains

This paper introduces a novel motion planning algorithm designed for a team of curvature-constrained tethered robots operating on sloped 3D terrains. Our approach addresses the critical issues of tether-terrain interaction, robot stability, and tether entanglement avoidance. The study focuses on a two-robot system, where stability is primarily dependent on tether tension, which is in turn limited by wheel traction. We propose a path-planning method that strategically utilizes terrain features (e.g., rocks) to augment tether tension through additional friction, thereby enhancing overall system stability. Our algorithm employs a modified tangent graph as the underlying structure for a hybrid A* search, incorporating stability constraints throughout the planning process. The proposed method is extensively evaluated through various simulation experiments, demonstrating its effectiveness in planning safe and efficient paths.