Full State Tracking and Formation Control for Under-Actuated VTOL UAVs

In this paper, a coupled-Attitude based trajectory tracking scheme is proposed to track both the position and attitude of under-Actuated unmanned aerial vehicles, and its application on formation control is further demonstrated. An intermediate attitude which is composed of the desired attitude and position information is designed in a two-stage framework, wherein the first stage is the controller design of a translational subsystem and the second stage is that of an attitude subsystem. By virtue of the intermediate attitude, trajectory tracking which includes both attitude and position is realized. The proposed intermediate attitude can be viewed as a bridge connecting the position and attitude motion, and it is a new approach for both single and multiple under-Actuated rigid bodies' control. Based on the approach of coupled-Attitude-based trajectory tracking, both the set point stabilization and formation tracking tasks for under-Actuated vertical takeoff and landing vehicles over a directed acyclic graph can be achieved. The performances of the proposed control laws are illustrated through numerical simulations.