CODE: Complete Coverage UAV Exploration Planner using Dual-Type Viewpoints for Multi-Layer Complex Environments

We present an autonomous exploration method for unmanned aerial vehicles (UAVs) for three-dimensional (3D) exploration tasks. Our approach, utilizing a cooperation strategy between common viewpoints and frontier viewpoints, fully leverages the agility and flexibility of UAVs, demonstrating faster and more comprehensive exploration than the current state-of-the-art. Common viewpoints, specifically designed for UAVs exploration, are evenly distributed throughout the 3D space for 3D exploration tasks. Frontier viewpoints are positioned at the centroids of clusters of frontier points to help the UAV maintain motivation to explore unknown complex 3D environments and navigate through narrow corners and passages. This strategy allows the UAV to access every corner of the 3D environment. Additionally, our method includes a refined relocation mechanism for UAVs specifically. Experimental comparisons show that our method ensures complete exploration coverage in environments with complex terrain. Our method outperforms TARE DSVP, GBP and MBP by the coverage rate of 64%, 63%, 54% and 49% respectively in garage-D. In narrow tunnels, ours and DSVP are the only two evaluated methods that achieve complete coverage, with ours outperforming DSVP by 35% in exploration efficiency.