Persistent UAV Formation Flight by Dynamic Agent Replacement and Leader Selection

First responders use Unmanned Aerial Vehicles (UAV) in disaster response to obtain a situational overview. Flying in a formation has the advantage of having multiple airborne sensors and cameras. However, UAV formations are limited in terms of flight time. In this paper we present a system that is capable of achieving persistent formation flight. The system does not need a central coordination unit and is self-organizing by triggering UAVs on the ground to take-off and join the formation whenever a UAV in the formation is about to run out of battery. The replacement process allows the formation to be kept intact for as long as possible. Onboard each UAV, the flight controller handles the formation-keeping and trajectory following while a higher level multi-agent-coordination unit accesses the flight controller to send commands. The leader-follower formation is designed to be rigid and independent of the number of UAVs present in the formation. A prototype consisting of four simulated UAVs was implemented as a proof of concept, which worked as expected.