This paper discusses energy extraction from atmospheric turbulence by small-and micro-uninhabited aerial vehicles. A nonlinear longitudinal dynamic model of a glider with elevators as the sole control input is used for the aircraft and feedback control laws for energy extraction are discussed. Using current measurements of wind speed and gradient the state which maximizes the gain in total energy is computed. A state feedback controller uses elevator input to regulate states to the optimal values. The state feedback control law is computed using LQR synthesis, and the state and input weight matrices which maximize energy gain are found using a search method. Simulation results of flights through sinusoidal gust fields and a thermal field show the performance of the proposed approach.
The increase in the maximum lift of an airfoil caused by small, movable tabs mounted on its upper surface has been explored in low-speed, wind-tunnel experiments at a chord Reynolds number of 1:0 £ £ 10 6 . These devices, herein called lift-enhancing effectors, have a chord that is 9% that of the airfoil and deploy passively at angles of attack approaching stall. Compared to the clean airfoil, the maximum lift coef cient is increased by approximately 20% with these simple devices. The lift increase is mainly caused by the effectors acting as "pressure dams," allowing lower pressures upstream of their location than would occur otherwise. At an effector the pressure recovers in a stepwise manner and continues downstream toward a trailing-edge value that is higher than that of the clean airfoil. This higher trailing-edge pressure also contributes to the increase in lift by allowing higher pressures over much of the lower surface. It has been shown that, in the absence of separation, properly installed effectors will lay ush on the surface and allow the airfoil to have the same performance in the low-drag range as the clean airfoil.
A theory-based aerodynamic model developed and applied to electrified powertrain configurations was intended to analyze the feasibility of implementing fully electric and serial hybrid electric propulsion in light-sport aircraft. The range was selected as the primary indicator of feasibility. A MATLAB/Simulink environment was utilized to create the models, involving the combination of proportional-integral-derivative controllers, aerodynamic properties of a reference aircraft, and powertrain limitations taken from off-the-shelf components. Simulations conducted by varying missions, batteries, fuel mass, and energy distribution methods provided results showcasing the feasibility of electrified propulsion with current technology. Results showed that the fully electric aircraft range was only 5% of a traditionally powered aircraft with current battery technology. Hybrid electric aircraft could achieve 44% of the range of a traditionally powered aircraft, but this result was found to be almost wholly related to fuel mass. Hybrid electric powertrains utilizing an energy distribution with their optimal degree of hybridization can achieve ranges up to 3% more than the same powertrain utilizing a different energy distribution. Results suggest that improvements in the power-to-weight ratio of the existing battery technology are required before electrified propulsion becomes a contender in the light-sport aircraft segment.
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