Tomas Musil presents SphereMap: Dynamic Multi-Layer Graph Structure for Rapid Safety-Aware UAV Planning

A flexible topological representation consisting of a two-layer graph structure
built on-board an Unmanned Aerial Vehicle (UAV) by continuously filling the
free space of an occupancy map with intersecting spheres is proposed in this
letter.
Most state-of-the-art planning methods find the shortest paths while keeping
the UAV at a pre-defined distance from obstacles. Planning over the proposed
structure reaches this pre-defined distance only when necessary, maintaining a
safer distance otherwise, while also being orders of magnitude faster than
other state-of-the-art methods. Furthermore, we demonstrate how this graph
representation can be converted into a lightweight shareable
topological-volumetric map of the environment, which enables decentralized
multi-robot cooperation. The proposed approach was successfully validated in
several kilometers of real subterranean environments, such as caves, devastated
industrial buildings, and in the harsh and complex setting of the final event
of the DARPA SubT Challenge, which aims to mimic the conditions of real search
and
rescue missions as closely as possible, and where our approach achieved the 2nd
place in the virtual track.