LAUSR

This paper employs bearing‐only measurements to address both constant and time‐varying formation tracking control for Vertical Take‐off and Landing (VTOL) Unmanned Aerial Vehicles. The time‐varying formation control paradigm is essential for practical scenarios where agents must navigate through arbitrarily shaped passages, necessitating changes in formation shape. Also, directed interaction among the agents is considered here, which is crucial considering the sensing limitations of the agents. By using bearing‐only measurements, the control laws are particularly suited for vision‐based applications that require only a camera sensor. Stability analysis is complicated by the use of an under‐actuated dynamic model rather than a kinematic model, as existing bearing‐only controllers for kinematic models do not guarantee stability for underactuated dynamic VTOL models. Some recent papers that considered VTOL models for bearing‐only formation tracking had serious flaws and an incorrect stability proof for the convergence of formation tracking error. For constant velocity tracking, the agents rely solely on bearings and bearing rates, while for time‐varying formation tracking, they incorporate their own velocity measurements along with the bearing measurements of neighbors. A Lyapunov‐based analysis demonstrates Global Uniform Asymptotic Stability for the formation tracking error dynamics in both cases. Additionally, in the time‐varying scenario, a directed graph is considered where each agent unidirectionally senses only two neighbors, thereby reducing sensing requirements compared to bidirectional sensing. Simulations further illustrate the effectiveness of the proposed control laws.