Research on multi-UAV communication connectivity maintenance based on dynamic programming

Abstract

With the continuous development of unmanned aerial vehicle (UAV) technology and its falling cost, UAV has been widely used in important fields, such as agriculture, industry, security, and military. In operation, UAVs often need to maintain communication connectivity with ground stations. However, in the case of long distance or shadowing, the quality of the wireless channels will be seriously degraded, which will affect the communication connectivity. To solve this problem, this paper considers deploying multiple UAVs as communication relays. In this paper, we select the long-term channel capacity as the optimization objective and propose two planning methods for UAV relays based on dynamic programming (DP): CMMP-AT and CMMP-OBO. The CMMP-AT method emphasizes the deployment of all relay UAVs at the beginning of the task. This method is simpler to implement, but the computational complexity is intolerable. The CMMP-OBO method proposes to deploy relay UAVs one by one according to the task requirements. Although the CMMP-OBO method may lose performance, it has a lower computational complexity and better scalability and can save more motion energy. The experimental results reveal that the CMMP-AT method requires 40.03 h to obtain the planning results for a two-relay scenario, whereas the CMMP-OBO method only needs 57.66 s and can save 3.87% motion energy. In addition, to precisely control the relay UAVs to follow the planned trajectory, this paper implements trajectory tracking, based on model predictive control (MPC), and realizes the simulation of the multi-relay UAV scenario in the VREP environment. The simulation results reveal that compared with the PID control method, the MPC method can track the planned trajectory more accurately. In two simulation scenarios, the tracking error of MPC is only 43.97% and 41.42% of the PID control method.