Multi-Floor Exploration for Ground Robots via an Incremental Reachable Graph and Structural Priors
For ground robots operating in multi-floor buildings, this work addresses the challenge of exploring overlapping surfaces, offering a practical solution with demonstrated improvements over baselines.
This paper introduces a multi-floor exploration framework for ground robots that uses an incremental reachable graph to handle overlapping traversable surfaces like stairs. The method improves exploration efficiency and mapping completeness in simulations and demonstrates real-time feasibility in real-world experiments.
Autonomous exploration of multi-floor buildings remains challenging for ground robots because conventional 2D and 2.5D maps cannot represent overlapping traversable surfaces such as stairs, ramps, and multiple reachable elevations. This letter presents a multi-floor exploration framework based on an incremental reachable graph. Built as a sparse graph over reachable support surfaces, the graph preserves potentially valid connectivity through tentative graph elements under sparse observations and enables stable, physically reachable frontier detection. To guide exploration beyond the currently mapped floor, we project task-zone priors from an explored floor to initialize a hypothetical graph on the target floor and reconcile it incrementally with incoming observations. A hierarchical planner then jointly reasons over confirmed and hypothetical structures for global guidance. In simulation, the proposed method demonstrates improved exploration efficiency and mapping completeness compared to evaluated baselines. Furthermore, onboard real-world experiments validate its practical feasibility and real-time performance.