Fixed-wing small, unmanned aerial vehicles usually fly in atmospheric boundary layers that are often un der the infl uence of turbulent environments. Inspired by nature' s flyers, an application of an energy-harvesting flight strategy for increasing the energy state of the aircraft is presented. This paper provides basic longitudinal fl ight dynamic model exposing the physics behind the process. It shows signifi cant power savings in fl ight with a sinusoïdal and stochastic wind profi le with active control of energy-harvesting. The active control based on optimized proportional gains was implemented for energy extraction from realistic atmospheric conditions, leading to significant energy savings for a 'bird-sized' vehicle. The paper reveals the equipment and necessary preparations for the fl ight test campaign. Moreover, it describes the design of a custom controller and its calibration in the wind tunnel against roll movements during pitching maneuvers. Finally, it investigates the benefits and potential of the automated process of energy-harvesting with simple proportional control through fl ight tests in a turbulent environment, validating the concept through the increased energy state of the aircraft.

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One of the major challenges of Mini-Unmanned Aerial Vehicle flight is the unsteady interaction with turbulent environment while flying in lower levels of atmospheric boundary layer. Following inspiration from nature we expose a new system for angle of attack estimation based on pressure measurements on the wing. Such an equipment can be used for real-time estimation of the angle of attack during flight or even further building of wind velocity vector with additional equipment. Those information can find purpose in control and stabilization of the aircraft due to inequalities seen by the wing or even for various soaring strategies that rely on active control for energy extraction. In that purpose, flying wing aircraft has been used with totally four span-wise locations for local angle of attack estimation. In-flight angle of attack estimation from differential pressure measurements on the wing has been compared with magnetic sensor with wind vane. The results have shown that pressure ports give more reliable estimation of angle of attack when compared to values given by wind vane attached to a specially designed air-boom. Difference in local angle of attack at four span-wise locations has confirmed spatial variation of turbulence in low altitude flight. Moreover, theoretical law of energy dissipation for wind components described by Kaimal spectrum has shown acceptable match with estimated ones.

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