A Voronoi-Based Safe Waypoint Generator for Hopping Robots Exploring Large Celestial Bodies

This work considers the generation of a safe waypoint roadmap for hopping robots traversing rugged terrains of large celestial bodies (such as planets and moons) which has disconnected safe regions cluttered with forbidden zones. Hopping robots suffer from positional drift at landing due to uncontrolled flying phase and after impact motions such as bouncing, tumbling, and slipping, which may lead to operation failure in rugged terrains. In this work, we propose a generalized Voronoi diagram based roadmap algorithm for generating a prospective waypoint set in safe regions, taking into account a user-defined safety margin that compensates for the undesirable robot drift at landing. With a ballistic motion based robot model and a graph search method, we demonstrate that the proposed approach can be integrated into a path planning framework which results a feasible waypoint sequence between any given start and goal positions within the safe regions. The generated waypoint sequence avoids forbidden zones with a given safety margin and ensures damage-free landing of the robot by satisfying an upper bound on maximum impact speed. The viability of the proposed approach is tested in a realistic planetary terrain scenario.