Reachability-based rendezvous guidance for autonomous refueling of unmanned aerial systems

This study proposes a rendezvous guidance system for the autonomous refueling of unmanned aerial systems. A rendezvous mission requires an unmanned aerial vehicle to approach an aerial tanker at a constant speed and a specified arrival angle. When speed control is unavailable, rendezvous missions become challenging, necessitating a sophisticated guidance function to meet the required criteria. The concept of reachability is proposed to enhance guidance capabilities and address the associated challenges. The relative motion between vehicles in two-dimensional space is considered, and a deviated-pursuit guidance scheme is employed to enable a vehicle to reach the tanker. The reachable region is calculated using a closed-form solution during mission execution, and a reference input is provided to the guidance module to achieve rendezvous. By incorporating the reachability concept, numerical simulations validate that the proposed guidance scheme effectively improves rendezvous performance, even under unfavorable initial conditions.