Flight Stability of Rigid Wing Airborne Wind Energy Systems

The flight mechanics of rigid wing Airborne Wind Energy Systems (AWESs) is fundamentally different from the one of conventional aircrafts. The presence of the tether largely impacts the system dynamics, making the flying craft to experience forces which can be an order of magnitude larger than those experienced by conventional aircrafts. Moreover, an AWES needs to deal with a sustained yet unpredictable wind, and the ensuing requirements for flight maneuvers in order to achieve prescribed control and power production goals. A way to maximize energy capture while facing disturbances without requiring an excessive contribution from active control is that of suitably designing the AWES craft to feature good flight dynamics characteristics. In this study, a baseline circular flight path is considered, and a steady state condition is defined by modeling all fluctuating dynamic terms over the flight loop as disturbances. In-flight stability is studied by linearizing the equations of motion on this baseline trajectory. In populating a linearized dynamic model, analytical derivatives of external forces are computed by applying well-known aerodynamic theories, allowing for a fast formulation of the linearized problem and for a quantitative understanding of how design parameters influence stability. A complete eigenanalysis of an example tethered system is carried out, showing that a stable-by-design AWES can be obtained and how. With the help of the example, it is shown how conventional aircraft eigenmodes are modified for an AWES and new eigenmodes, typical of AWESs, are introduced and explained. The modeling approach presented in the paper sets the basis for a holistic design of AWES that will follow this work.

Insect Wing Buckling Influences Stress and Stability During Collisions

Flapping insect wings frequently collide with vegetation and other obstacles during flight. Repeated collisions may irreversibly damage the insect wing, thereby compromising the insect’s ability to fly. Further, reaction torques caused by the collision may destabilize the insect and hinder its ability to maneuver. To mitigate the adverse effects of impact, some insect wings are equipped with a flexible joint called a “costal break.” The costal break buckles once it exceeds a critical angle, which is believed to improve flight stability and prevent irreversible wing damage. However, to our knowledge, there are no models to predict the dynamics of the costal break. Through this research, we develop a simple model of an insect wing with a costal break. The wing was modeled as two beams interconnected by a torsional spring, where the stiffness of the torsional spring instantaneously decreases once it has exceeded a critical angle. We conducted a series of static tests to approximate model parameters. Then, we used numerical simulation to estimate the peak stresses and reaction moments experienced by the wing during a collision. We found that costal break increased the wing’s natural frequency by about 50% compared to a homogeneous wing and thus reduced the stress associated with normal flapping. Buckling did not significantly affect peak stresses during collision. Joint buckling reduced the peak reaction moment by about 32%, suggesting that the costal break enhances flight stability.

Study on longitudinal stability of ducted vertical take-off and landing fixed-wing UAV

The longitudinal flight stability of the ducted vertical take-off and landing fixed-wing UAV during the flight state of hovering and transition is studied. Firstly, based on the Blade-Element Momentum Theory (BEMT) and experimental data, a coaxial dual-rotor ducted aerodynamic model and a thrust ducted aerodynamic model based on characteristic cross-section calculations are established. The model parameters are identified according to the experimental data. Secondly, a UAV flight dynamics model with thrust duct deflection is established according to the six-degree-of-freedom equations. Finally, the case UAV was used to solve the longitudinal balance and stability analysis of hovering and transition state with the established model method, and compared with the hovering experimental results. The results show that the UAV flight dynamics model combined with the ducted dynamic model established in the article can accurately describe the longitudinal flight stability characteristics of this type of aircraft.

Investigations of Lift and Drag Performances on Neo-Ptero Micro UAV Models

This paper presents the investigation and improvement of lift and drag characteristics of Neo-Ptero micro-UAV models based on the virtual wind tunnel method. Despite its successful development and flight stability, the lift and drag coefficients characteristics of the current Mark 1 Neo-Ptero remain unknown. To improve the Mark 1 Neo-Ptero performances, Mark 2 Neo-Ptero model has given a new unsymmetrical airfoil wing configuration. The computational aerodynamic analysis was executed and focused on certain lift and drag coefficient characteristics. Lift coefficient results showed that Mark 2 improved in overall lift characteristics such as zero-lift angle, maximum lift magnitude and stall angle magnitude. Conversely, Mark 2 model suffered a slightly higher drag coefficient magnitude and more significant drag increment percentage than Mark 1. However, the trade-off between superior lift magnitude and minor drag generation induced by Mark 2 boosts the model’s aerodynamic efficiency performances but is only limited at early angle stages.

DESIGN OF MULTIFUNCTIONAL UAV OF ROTOR TYPE ON THE BASE OF FIRMWARE ARDUPILOT

In this work, a multifunctional rotor-type UAV (hexacopter) was designed based on the Arducopter ver.4.0.7 firmware for FMUv3 devices. Experimental tuning of the firmware parameters for a given UAV geometry, its weight, propeller group, flight stability in a gusty wind for navigation modes has been performed. It is shown that this flight controller can use all the documented features of the Ardupilot firmware, unlike the Pixhawk1 1M. Experimentally, on the basis of numerous flights, it was revealed that firmware using a mathematical apparatus based on the extended Kalman filter (Arducopter 4.0.7) gives better flight results in navigation modes than firmware based on the use of a complimentary filter (INAV, Betaflight - rescue mode). The possibility of controlling additional equipment using a flight controller is shown using the example of dropping a load at a given point of the trajectory. The results of telemetry were obtained during the automatic flight of the hexacopter along a given trajectory based on the installed sensors. It is shown how, using the ground station software, it is possible to obtain two-dimensional and three-dimensional graphical representations of telemetry data for analyzing the flight of a copter with its subsequent fine tuning. The possibility of constructing and constructing a three-dimensional trajectory of the UAV flight according to telemetry data using the Google Earth program has been studied. Considered the fine tuning of UAV flight modes using the Ardupilot firmware parameters. The parameters are identified that are basic for ensuring maximum flight stability in abruptly changing conditions, for example, during sudden braking, maneuvers, gusty wind. The range of variation of these parameters and their values have been determined experimentally. The parameters of the PID controller were tuned to ensure a smooth and stable flight in navigation modes. In work with the use of a servo drive, a load dropping device has been designed, which can be triggered automatically when flying along a trajectory, and when commanding from the control panel when approaching a given point, which is visually viewed using the Mission Planner.