6. Conclusions
The paper presented a novel UWB positioning network for an autonomous UAS landing. The UAS positioning during a landing is passive such that a UWB signal is emitted from an UAS. And, the UAS position is computed on the ground and is sent back to the UAS through a protected aviation communication channel. The anchor network geometry was determined from using Binary Integer Linear Programming-based search algorithms. The algorithms were applied to a modeled runway and landing paths having glideslopes between 5 to 13 degrees in a relatively small local municipal airport. The resultant optimal network consisted of a total 10 anchors: 6 anchors in the 10 meter height antennas and 4 anchors on the ground. Simulation based on the resultant optimal network presented the lateral, longitudinal, and vertical positioning accuracies in the presumed landing paths. Overall, the positioning network provides excellent lateral and vertical positioning accuracy for a landing operation. The lateral positioning accuracy was better than 40 cm (1σ ) in all of the user spaces, and the vertical accuracy is as good as 9 cm (1σ ) at the flare point, which is the most critical point in a landing. The longitudinal positioning accuracy was relatively poorer when an UAS is beyond 200 m from the flare point. This can be improved by placing another anchor around the initial decent point. It is expected that the proposed UWB anchor network would be a viable solution for a fixed wing UAS auto landing with the lower cost and higher positioning accuracy compared to current manned aircraft auto landing systems such as ILS or GBAS.
