Robust Linear-Velocity-Free Formation Tracking of Multiple Quadrotors With Unknown Disturbances

This article addresses the problem of quadrotor formation control with inaccessible linear velocity and the unknown disturbances under directed interaction topologies. In this article, considering the unknown disturbances act in both the translational and rotational motions of each underactuated quadrotor, a hierarchical distributed disturbance rejection controller is developed for the quadrotor formation. In the outer loop, an observer-based translational controller is designed to achieve the desired formation over directed interaction topologies. To estimate the inaccessible linear velocity measurements, a uniform differentiator is designed for each quadrotor using only the position information. In the inner loop, a robust geometric attitude controller is developed based on a super-twisting algorithm. The proposed controllers can reach disturbance rejections in the whole frequency domain as much as desired and achieve asymptotic formation tracking within the appointed time. The stability analysis is presented using the Lyapunov stability theory on cascaded systems, and the effectiveness of the proposed control strategy is demonstrated through numerical simulations.