Papers by Keyword: Flapping Wing

Abstract: A flapping wing mimicking the Black Headed Gull was developed and tested for its kinematics. All the individual joints in the gull wing, namely the shoulder, elbow and wrist joint were mimicked with their corresponding functionalities. The shoulder joint is designed to control the flapping frequency, flapping amplitude, flapping plane and the speed of the upstroke-downstroke. Similarly, the elbow and wrist joints control the upstroke span reduction and twisting of the wing, respectively. Geometry, inertia, mass and frequency data of the gull were used to model the wing. A control input program was designed for the independent control of all the 6 joints (3 per wing). The motion of the manufactured wing system was verified using LASER Displacement Sensor.

Abstract: In the present study, the aerodynamic characteristics such as time-averaged lift and drag generation of two flexible membrane (latex thin and thick) wings with different skin flexibilities are compared with those of a conventional rigid (wood) wing to assess the effects of skin flexibility (rigidity) on the aerodynamic performance for flapping flight applications. The experiments are performed in an open circuit wind tunnel of non-return airflow with a test section of (0.3m x 0.3m) and is capable of speeds from 0.5 to 30 m/s. The time-averaged lift and drag as functions of flapping frequency, forward flight velocity and the orientation angle of the flapping motions with respect to the incoming flows are measured by using a strain gauge balance and KYOWA PCD-300A sensor interface data acquisition system. It has been found that flapping motion would bring significant aerodynamic benefits when the flapping flight is in unsteady state regime, with advance ratio less than 1.0. The aerodynamic benefits are found to decay exponentially with the increasing advance ratio. Flapping motion is found to become detrimental for high speed flight applications. It is also observed that the skin flexibility has considerable effect on the aerodynamic performance. The flexible latex thick wing is found to have better overall aerodynamic performance over the rigid wing, especially for low speed applications. The wood (rigid) wing exhibited better lift production performance in quasi steady regime.

Abstract: Micro Air Vehicle (MAV) has the capability to fly autonomously in complex environments which enables human to conduct surveillance in areas which are deemed too dangerous or in confined spaces that does not allow human entry. Research and development of MAVs aim to reduce their size further, thus novel techniques need to be explored in order to achieve this objective while still maintaining the MAVs’ current performance. In this paper, a conceptual design of an MAV with a main drive system using shape memory alloy (SMA) actuator to provide the flapping motion is proposed. SMA is considered superior to other smart materials due to its efficiency and large energy storage capacity. By incorporating SMA in the flapping wing MAV, it will provide users the flexibility to add more payloads by reducing bulky cables or reduce operating cost by using less fuel. However, there are some drawbacks in using SMAs such as nonlinear response of the strain to input current and hysteresis characteristic as a result of which their control is inaccurate and complicated.

Abstract: Flapping wing aerial vehicles continue to be a growing field, with ongoing research into unsteady, low Reynolds number aerodynamics and micro fabrication. However research into deformation and stress of flapping wing continues to lag, especially based on composites model. One flapping cycle was divided into twelve segments, and maximum defmortion and stress were calculated in each segment. The results show that the maximum sdeformation at the beginning stages of downstroke is 19% larger than the maximum deformation at the beginning stages of upstroke, and the maximum stress at the beginning stages of downstroke is 29.9 larger than the maximum stress at the beginning stages of upstroke. This research is helpful to answer that why insect wings are so perfect through long evolution, thus improving the design of flapping-wing aerial vehicles.

Abstract: The maximum deformation and stress are compared based on Mooney-Rivlin Model and Linear Model for flapping wing. One flapping cycle was divided into twelve segments, and maximum deformation and stress were calculated in each segment. The results show that max deformation and stress all occur at the beginning of downstroke, the max deformation adopted Mooney-Rivlin model is 25 percent of the max deformation adopted the linear model, and the max stress adopted Mooney-Rivlin model is only 0.37 percent of the max stress adopted the linear model. Mooney-Rivlin Material is very suitable for the membrane flapping wing.

Abstract: To investigate the aerodynamic performance of a flexible flapping wing aircraft, a flapping-wing system were design and an experiment were set up to measure the unsteady aerodynamic forces of the flapping motion. The thrust formula and resistance formula described aerodynamic forces. The lift and thrust of this mechanism were measured for different angles of attack and wind velocities. Results indicate that the thrust increases with the flapping frequency and the lift increase with the wind velocity, while the lift coefficient decreases while the velocity increases. It is realized that the wing’s transformation which imitated birds leads less resistance when flapping upward which impacts the aerodynamic lift generation and the bionic winglet leads to a change in the leading edge vortex and span-wise flow structures, which decrease the airflow’s backward pull. Models were introduced which were used in the design process and show its aerodynamic performance. The flexible flapping wing vehicle is still an open research area.

Abstract: MAV- Micro Air Vehicle which acts like bird has attracted many studies because of outstanding aerodynamic property. Former studies on birdlike MAV with flapping wing had just focused on the flapping motion, but passed over the change of flapping angular velocity and deformation of wing, therefore lost the good aerodynamic capacity. One new mechanism of the birdlike MAV is designed and studied. The mechanism can bring out 3 motions at one time, including flapping, spanning and twisting, so has movement as bird. The kinematic performance including the flapping angle, flapping angular velocity, and the folding angle etc., has been studied and compared with other relative works. The design can help the birdlike aircraft into reality.

Abstract: The goal of our research is to develop a micro air vehicle (MAV) that is strongly stable in a wind gust. After observation of flights of an insect and a bird, we conjectured that an ornithopter would be a promising candidate as a high-performance MAV. In this paper we demonstrate the clear advantage of an ornithopter over an airplane with propellers. The variations in the aerodynamic forces acting on the two aircrafts, which generate the same thrust under the condition of no wind gust, were compared when they encountered gusts of wind. The consumed power, or alternately the period of one cycle of flapping motion and that of one rotation of propeller(s), remained constant before and after they encountered a wind gust. The following results were obtained: The variations of the aerodynamic force of an ornithopter by vertical and frontal wind gusts were slightly smaller than those of an airplane with one or two propellers. The variation in the aerodynamic force of the former by a side wind gust was smaller than that of the latter when the tip speed of the propeller and the flapping amplitude of the ornithopter were small.

Abstract: The stress change of membrane flapping-wing aerial vehicle that used Moon-Rivlin model was calculated in one flapping cycle. One flapping cycle was divided into twelve segments, aerodynamic force and inertia force in each segment were calculated, the stress distribution could be gotten. The results show that: at the beginning of upstroke and at the beginning of downstroke, the stress of flapping-wing is maximum; the stress of downstroke near the flapping symmetry position is minimum, and the stress of upstroke near flapping symmetry position is another minimum peak stage.

Abstract: The unsteady viscous flow fields of dual flapping airfoils in tandem configurations are simulated by a Navier-Stokes Solver based on dynamic deformable hybrid meshes. Aerodynamic interactions of three motion models are studied including flapping fore airfoil with fixed aft airfoil, two airfoils flapping in phase and out-of-phase. The results indicate that the aft airfoil in the wake of the flapping fore airfoil has great influence on the aerodynamic performance. When the fore airfoil flaps with a fixed aft airfoil, the thrust generation and thrust propulsive efficiency were enhanced by 65% and 44% respectively, compared to that of single flapping airfoil. When the two airfoils stoke in phase, the thrust generation is twice over that of single flapping airfoil. However the out-of-phase stroking has relatively much lower thrust.