Differentiator-based Formation Control of Quadrotors with Bearing-only Measurements

In this article, a bearing-only formation control scheme was presented for VTOL UAVs based on differentiators, which uses only inter-agent bearing measurements. The task of each UAV is to maintain a predetermined bearing with its neighbors without the measurement of position information and velocity information. Notably, the bearing-only formation tracking controller utilizes a filter-like method to conquer the lack of bearing rate measurement in the outer loop. In addition, the lack of linear velocity and acceleration measurement is handled by an arbitrary-order differentiator in the inner-loop attitude controller. Finally, the effectiveness of the proposed control strategy is illustrated by the Lyapunov stability theory and numerical simulations. It exhibits that both the estimation errors and control errors stabilize to zero under the corresponding topology and properties of bearing rigidity.