Experimental Investigation of Aerodynamics of Feather-Covered Flapping Wing

Avian flight has an outstanding performance than the manmade flapping wing MAVs. Considering that the feather is light and strong, a new type of the flapping wing was designed and made, whose skeleton is carbon fiber rods and covered by goose feathers as the skin. Its aerodynamics is tested by experiments and can be compared with conventional artificial flapping wings made of carbon fiber rods as the skeleton and polyester membrane as the skin. The results showed that the feathered wing could generate more lift than the membrane wing in the same flapping kinematics because the feathered wing can have slots between feathers in an upstroke process, which can mainly reduce the negative lift. At the same time, the power consumption also decreased significantly, due to the decrease in the fluctuating range of the periodic lift curve, which reduced the offset consumption of lift. At the same time, the thrusts generated by the feather wing and the membrane wing are similar with each other, which increases with the increase of flapping frequency. In general, the aerodynamic performances of the feather wing are superior to that of the membrane wings

Longitudinal Trim and Dynamic Stability Analysis of a Seagull-Based Model

Understanding the mechanisms of trim and flight stability in birds is critical to guide the design of bionic micro air vehicles. The complex movements (plunging, sweeping, twisting) and morphing of wings always keeps the flapping flight of birds in dynamic equilibrium, which makes it difficult to determine the critical factors of trim and stability. Hence, a model has been developed that takes real complex movement and the calculation of unsteady aerodynamics into consideration. Two trim methods, including wash-out and forward-sweep, have been used to achieve equilibrium in the longitudinal direction. It is interesting to find that these two methods are both important to realize a larger take-off weight, lower power consumption, and stronger longitudinal stability. This implies that the seagull probably uses both of them to obtain the requirement of equilibrium and stability, which further inspires the design of seagull-inspired micro air vehicles

Reliability modeling for competing failure systems with instant-shift hard failure threshold

There are many researches about the modeling for system under multiple dependent competing failure processes (MDCFP) in recent years. Typically speaking, those failure processes are composed by degradation process (soft failure) and random shock process (hard failure). The threshold of hard failure is a fixed value in previous papers which is not compliance with the engineering practices. Threshold means the ability to resist external random shocks which is also shifting with time due to the usage of system. Thus, this paper establishes a model for MDCFP with instant-shift hard threshold. The hard failure threshold changes with time instantaneously and it is also influenced by external shocks. Afterwards, system reliability model is built. The effectiveness of presented model is demonstrated by the reliability analysis of the micro-engine of Sandia National Laboratories. In addition, sensitive analysis is performed for specific parameters.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Dynamic Soaring Parameters Influence Regularity Analysis on UAV and Soaring Strategy Design

Dynamic soaring helps albatross achieve long-distance migration. From a bionic view, dynamic soaring has great potential to enhance unmanned aerial vehicles (“UAVs”) flight range and endurance. The previous application studies focus on flight strategies to guide UAV soaring. However, the energy harvesting efficiency problem emerges. The lack of clear dynamic soaring influencing factors hinders dynamic soaring UAV design and flight strategy design from a theoretical perspective. Hence this paper aims to analyze the influence law of different UAV mass, initial airspeed, and entering angle. Trajectories and flight data in different factors are obtained through trajectory optimization. The results show that UAV mass has a positive influence on energy harvesting. The initial airspeed and entering angle affect both energy efficiency and trajectory. For UAV design, weight balance needs to be considered rather than a pursuit of the lightest. For flight strategy design, finding an optimal initial state will improve energy efficiency

Effect of Laser Weapon Turret Size onAircraft Combat Effectiveness

Airborne laser weapon system can increase the survivability of the aircraft by active defense. In order to obtain longer fire range, a large diameter of the airborne laser weapon turret is required, which may cause negative influence to the aircraft. The influence of turret diameter on aerodynamic and stealth performance of the aircraft is analyzed by means of computational fluid dynamics method and physical optics method. And the influence of turret diameter on combat effectiveness is analyzed with agent-based combat simulation. The results show that the increase of turret diameter will lead to a slight decrease of aircraft speed, while the influence quantity of laser turret to aircraft speed is within 2%. In the meantime, the increase of turret diameter increases the front RCS (Radar Cross Section) of the aircraft, an diameter of 30, 50 and 70 cm of laser turret could lead to an increase of 64%、173% and 282% of the aircraft RCS. The 50 cm diameter design could increase the most mission effectiveness, which is 77.2%

Modeling and Application of Dynamic Soaring by Unmanned Aerial Vehicle

Albatross have a significant gliding ability called dynamic soaring. In the bionic study, dynamic soaring has a great potential to enhance Unmanned Aerial Vehicles (UAVs) flight range and endurance. The previous study on dynamic soaring mainly focused on the energy harvesting mechanism, trajectory optimization, and flight test. However, the longtime optimization became the challenge of the UAV dynamic soaring application. Similarly, due to the difficulty of the dynamic soaring test flight, both the feasibility of dynamic soaring application and the energy harvesting mechanism model’s accuracy lack validation. This paper proposes a new method to give a dynamic soaring trajectory, and a flight simulation program is built to realize the dynamic soaring flight test. The results show that the new method can guide the UAV to achieve dynamic soaring and verify the improvement of its flight performance through dynamic soaring. Meanwhile, the accuracy of the energy harvesting mechanism model is verified. The results indicate the indirect way to achieve the UAV dynamic soaring and provide a flight test foundation for a profound dynamic soaring mechanism study

Active Disturbance Rejection Attitude Control for a Bird-Like Flapping Wing Micro Air Vehicle During Automatic Landing

To solve the attitude control problem of bird-like flapping wing micro air vehicles (FWMAVs) during automatic landing, an active disturbance rejection control (ADRC) architecture is proposed in this paper. This control scheme takes into account the attitude control of flapping, transition and gliding modes in the process of automatic landing. To verify the control effect, the aerodynamic estimation method of the flapping wing based on quasi-steady theory and the dynamics of an FWMAV in Lagrangian form are applied in the simulation. The proposed control architecture consists of two independent ADRC controllers to stabilize the attitude of the pitch and roll channels. The system disturbance and the coupling effects between channels are estimated by an extended state observer (ESO) and compensated in real time in the control output. The convergence of the ESO and ADRC is proven. Simulation results show that even if the aircraft is in different flight modes, the ADRC controller can track the target trajectory quickly and accurately. Then, to realize automatic landing in a real environment, a simplified two-stage landing trajectory is designed. A landing test is carried out on this basis. The test results show that ADRC can not only stabilize the flight attitude in flapping mode but also obtain a satisfactory control accuracy and convergence speed when the aircraft is in the transition and gliding modes, confirming its usefulness in automatic landing