Coordinated Tracking of a Stationary Target in the Presence of Wind with Collision Avoidance Guarantees

This paper proposes a vector field guidance law for a team of Unmanned Aircraft (UA) to track a stationary target in a circular path at a fixed stand-off radius from the position of the target. A phasing Lyapunov function is also given and, using the Lyapunov stability analysis it is ensured that the two UA will maintain a constant phase difference between them once they converge to the stand-off radius. To counter the effect of a constant background wind, the vector guidance law is modified using a variable scaling factor. During the transient phase, i.e., before converging to the stand-off radius, the possibility of having a collision between the two UA is avoided by using a Control Barrier Function (CBF) approach to generate constraint based input control functions which avoids the collision between the two UA. We also propose an algorithm for periodic and event-based communication to reduce the frequency of the information exchange between UA. Simulation results for the cases of constant communication between the two UA, periodic communication, and an event-based communication are presented which verifies the efficacy of the proposed methodology.