Real-Time First-Order Guidance Strategies for Trajectory Optimization Through Wind Energy Utilization

This paper presents real-time guidance strategies for unmanned aerial vehicles that can be used to enhance their flight endurance by using in situ measurements of wind speeds and wind gradients. In these strategies, periodic adjustments would be made in the airspeed and/or heading angle command for the unmanned aerial vehicle to minimize a projected power requirement at some future time. In this paper, unmanned aerial vehicle flights are described by a three-dimensional dynamic point mass. Onboard closed-loop trajectory tracking logics that follow airspeed vector commands are modeled using the method of feedback linearization. A generic wind field model is assumed that consists of a constant term plus terms that vary sinusoidally with respect to the location. To evaluate the benefits of these strategies in enhancing unmanned aerial vehicle flight endurance, a reference strategy is introduced in which the unmanned aerial vehicle would seek to follow the desired airspeed in a steady level flight under zero wind. A performance measure is defined as the average power consumption both over a specified time interval and over different initial heading angles of the unmanned aerial vehicle. A relative benefit criterion is then defined as the percentage improvement of the performance measure of a proposed strategy over that of the reference strategy. Extensive numerical simulations are conducted. Results demonstrate the benefits and trends of power savings of the proposed real-time guidance strategies.