Bearing-only Formation Maneuvering for UAV Swarm over Directed Interaction Topologies

This research paper addresses the formation control problem in a swarm of quadrotor unmanned aerial vehicles (UAVs) over directed interaction topologies, with the primary objective of achieving persistent motion based on bearing measurements. A novel bearing-only formation controller is proposed, eliminating the need for relative position or linear velocity measurements between quadrotors. Specifically, a distributed hierarchical formation control scheme is adopted for the quadrotors. This scheme consists of an outer-loop translation controller designed for target formations using only bearing vector measurements, as well as an inner-loop attitude controller for precise attitude adjustments. To overcome the absence of bearing rate measurement in the translational controller, a filter is introduced to estimate it, effectively compensating for the lack of linear velocity measurement. Additionally, a differentiator is employed to estimate the high-order control input of the translational dynamics, enabling convenient derivation of the desired angular velocity and its derivatives required for the torque controller. The stability analysis of the underactuated systems of multi-UAVs under directed graphs is conducted using Lyapunov stability theory. Simulation results demonstrate the convergence properties of the proposed protocols, while real-world tasks validate its practicality.