A Moving Path Following Approach for Trajectory Optimization of UAVs: An application for target tracking of marine vehicles

In this paper we propose a novel numerical approach to the design of smooth trajectories for fixed-wing Unmanned Aerial Vehicles (UAVs) with applications to target tracking of marine vehicles. Given a desired geometric path with respect to a possible moving target vehicle, we are interested in computing a feasible UAV trajectory that best approximates in L-2 sense the desired geometric moving path with a specified airspeed profile assigned on it. Due to communication range limitations (e.g., the UAV is operating as a wireless communication relay between a target vehicle and a ground station), the UAV trajectory needs to satisfy given path constraints. Space-varying wind is also taken into account. We address this problem by taking a Virtual Target Vehicle (VTV) perspective. We set up a suitable optimal control problem based on the error coordinates between the UAV and the VTV. We solve the optimal control problem numerically by using PRONTO, a very versatile control optimization tool enabling to deal with a wide variety of trajectory functionals and constraints. We provide and discuss numerical computations based on a practical scenario where an Autonomous Surface Vehicle (the target vehicle) transmits data to the UAV which sends them back to a ground station.