Coverage path planning by swarm of UAVs for UGV traversability analysis

In rough or risky environments, such as minefields, landslides or volcanic eruptions, it is extremely complex to plan safe trajectories for an Unmanned Ground Vehicle (UGV), since both robot stability and path execution feasibility must be guaranteed. In these scenarios, the adoption of a swarm of Unmanned Aerial Vehicles (UAVs) to survey the area and reconstruct 3D models of the environment can be really helpful. In this paper we will present a complete solution combining three different aspects. The first is the coverage path planning and concerns the definition of UAV trajectories for photogrammetric aerial image acquisition. When non-coverable zones are present, a suitable decomposition into subregions of the whole area to survey is performed. The second aspect is then related to the use of a swarm of UAVs to implement the coverage in a parallel way. A solution to assign the different regions among the flying vehicles will be presented, which optimises the path length of the whole swarm. The last aspect concerns the path planning of the ground vehicle, by means of a traversability analysis performed on the terrain 3D model (reconstructed from the previous aerial survey). The computed paths will be optimal in terms of difficulty of moving across the rough terrain. The results of each step of the overall approach will be shown.