Flapping Wing Micro Air Vehicle Research Articles

One-way FSI analysis of bio-inspired flapping wings

Aerodynamics and structural dynamics of the insect wings are widely considered in flapping wing micro air vehicle (FWMAV) applications. In this paper, the aerodynamic characteristics of the three-dimensional flapping wing models mimicked from the bumblebee and hawkmoth wings are numerically investigated under steady flow conditions. This study aims to simulate the one-way fluid-structure interaction (FSI) of these bio-inspired wings by transferring the aerodynamic load obtained from the computational fluid dynamics (CFD) into the finite element method (FEM) solver as a pressure load. The static aeroelastic responses of the wings under the pressure load are compared for different materials, namely, cuticle, aluminium alloy, and titanium alloy at various angles of attack (α = 0°-90°). CFD analysis shows that the hawkmoth wing model at α = 5° has the highest lift-to-drag ratio (L/D). FSI analysis demonstrates that the cuticle hawkmoth wing model at α = 90° undergoes the highest tip deflection.

Experimental Studies of Tail Shapes for Hummingbird-Like Flapping Wing Micro Air Vehicles

The stability of flying of a hummingbird-like flapping-wing micro air vehicle (MAV) has been challenging. In this paper, experimental studies are reported on the tail shapes of hummingbird-like flapping-wing MAVs, since tails play an important role in-flight stability. Dynamics parameters of hummingbird tails are firstly studied and evaluated. Then man-made tails inspired by the natural hummingbirds are designed, manufactured and optimized for experimental tests. The results show that lift generated by the tail is independent of a fan angle, whereas the pitch moment is related to the fan angle. Further, the tail can be applied to stabilising hovering twin-wing flapping wing MAVs.

Force generation of smooth and corrugated airfoil performing unsteady motions at low Reynolds number

Structurally, corrugated airfoil for flapping wing MAV applications is more desirable due to its increased strength. Therefore, any aerodynamic (penalty) effects due to corrugation on such airfoil have found considerable attention. The objective of the paper is to computationally examine the effects of corrugation on an elliptical airfoil performing translation and pitching motion at Re = 100 by comparing it with the performance of a smooth NACA 0012 airfoil. The forces and the flow structures generated over the airfoils during their unsteady motion are solved using Navier–Stokes equations. These unsteady motions include the airfoil accelerating from the rest position and quickly pitching up in a constant free stream. The two airfoils are considered in the study with 50 and 100 equally spaced perturbations on the upper and the lower surfaces, respectively. The surface of a standard ellipse has been modified with the regular perturbations or ‘corrugation’ of the order of 1% c on the upper and the lower surfaces. The current study reveals that during the airfoil acceleration from the rest to U and, subsequently, in a constant velocity translation, the corrugated airfoils (regular surface perturbations) have similar behavior of the force and the moment coefficients (also similar vorticity plots) in comparison with the smooth airfoil. However, it is also found that for the fast and the slow pitching motion in a free stream, the corrugated airfoil (after certain angle of attack) has slightly lower values of the lift and the moment coefficients in comparison with the smooth airfoil; which is due to the small effect of corrugation on the velocity profile. It is concluded that the unsteady effect dominates the geometric differences (smooth versus corrugated airfoil); therefore, corrugated airfoil can be utilized to provide structural strength for flapping wing MAV applications.

Active Flow Control of Flapping Airfoil Using Openfoam

ABSTRACTThe concept of the fixed wing Micro Air Vehicles (MAVs) has received increasing interest over the past few decades, with the principal aim of carrying out the surveillance missions. The design of the flapping wing MAVs still is in infancy stage. On the other hand, there has been increasing interest over the flow control using plasma actuators in worldwide. The aim of this research is to study the flow control of a flapping airfoil with and without plasma actuation in OpenFOAM. The OpenFOAM CFD platform has been used to develop our own plasma solver. For the plasma induced turbulence in the flow regime, k-ε turbulence model was adopted to address the interaction between plasma and fluid flows. For the plasma-fluid interaction, we use reduced-order modelling to solve the plasma induced electric force. A two dimensional NACA0012 flapping airfoil without plasma actuation study has been benchmarked with previous published literature. We have not only focused on the active flow control but also analyzed the important parameter reduced frequency at different values, those are 0.1, 0.05 and 0.025. Reduced frequency (κ) is very important parameter of an airfoil in the unsteady motion. Our major contribution is testing the several reduced frequencies with the plasma actuation. The positive and beneficial effects of the plasma actuator for all cases have been observed. From the observed results, the flapping with plasma actuation at reduced frequency of 0.1 showed the 14.285 percent lift improvement and the 16.19 percent drag reduction than the flapping without plasma actuation at the respective dynamic stall angles. The maximum lift coefficient is increased with the increase in reduced frequency. In overall, plasma actuators are effective in the flow control of a flapping airfoil. In future, the combination of the flapping with plasma actuators will be a promising application to boast the maneuverability of MAVs.

Aerodynamic Performance of a Passive Pitching Model on Bionic Flapping Wing Micro Air Vehicles.

Reducing weight and increasing lift have been an important goal of using flapping wing micro air vehicles (FWMAVs). However, FWMAVs with mechanisms to limit the angle of attack (α) artificially by active force cannot meet specific requirements. This study applies a bioinspired model that passively imitates insects' pitching wings to resolve this problem. In this bionic passive pitching model, the wing root is equivalent to a torsional spring. α obtained by solving the coupled dynamic equation is similar to that of insects and exhibits a unique characteristic with two oscillated peaks during the middle of the upstroke/downstroke under the interaction of aerodynamic, torsional, and inertial moments. Excess rigidity or flexibility deteriorates the aerodynamic force and efficiency of the passive pitching wing. With appropriate torsional stiffness, passive pitching can maintain a high efficiency while enhancing the average lift by 10% than active pitching. This observation corresponds to a clear enhancement in instantaneous force and a more concentrated leading edge vortex. This phenomenon can be attributed to a vorticity moment whose component in the lift direction grows at a rapid speed. A novel bionic control strategy of this model is also proposed. Similar to the rest angle in insects, the rest angle of the model is adjusted to generate a yaw moment around the wing root without losing lift, which can assist to change the attitude and trajectory of a FWMAV during flight. These findings may guide us to deal with various conditions and requirements of FWMAV designs and applications.

Mechanism and scaling of wing tone generation in mosquitoes

The generation of sound from flapping (i.e. wing tones) of mosquito (Culex) wings is investigated using computational modeling. The flow field around the wing is simulated by solving the incompressible Navier–Stokes equations using a sharp-interface immersed boundary method, and the aeroacoustic sound is predicted by the Ffowcs Williams and Hawkings equation using data from the aerodynamic simulations. In addition to the aerodynamics, the characteristics of mosquito’s wing tone, spectral directivity patterns, and generation mechanisms are investigated. The effects of wing-beat frequency and stroke amplitude are also studied, and scaling analysis for the mean lift, mechanical power, and overall wing tone sound power are performed to understand the effects of the wing shape and kinematics parameters. The analysis shows that the high wing aspect-ratio, high wing beat frequency, and small stroke amplitude adopted by mosquitoes enable efficient generation of high-intensity wing-tones for acoustic communications. The present findings may also apply to the optimized noise control in the flapping-wing micro air vehicles (FWMAV).

구동기와 센서를 고려한 날갯짓 초소형 비행체의 외란관측기 기반 제어

This paper presents the controller design with a disturbance observer of a Flapping-Wing Micro Aerial Vehicle (FWMAV) considering actuator and sensor model. FWMAVs experiences periodic motions of the wings and their resulting aerodynamic changes. However, the controller design for the FWMAVs is mainly based on linear control with linearized models for a single period of flapping with Floquet theory. This approach is vulnerable to uncertainties from aerodynamics and fabrication errors and external disturbances. In this background, this study applies a disturbance observer based controller based on a simple double integrator model for a FWMAV dynamics. For this, numerical modeling considering an actual FWMAV is done by taking into account flapping kinematics, aerodynamics, actuators, and sensors. To verify the proposed control strategy, numerical simulations are performed in a disturbed flight situation.

외란 관측기를 통한 날갯짓 비행체의 강건 종방향 자세 제어

Flapping-wing micro air vehicles (FWMAVs) are interesting flight platforms due to their energy efficiency, camouflage ability and agility. However, these FWMAVs produce limited forces and moments due to their small scale and complex dynamics, so most studies have been conducted in indoor environments where external disturbance is excluded. In order for these bio-inspired robots to perform various tasks in outside, an ability to react robustly to external disturbance is essential. In this paper, we employ a robust controller called disturbance observer for attitude control of a FWMAV. Before designing a controller, we derive the attitude dynamics of the FWMAV based on experimental data. Then, we validate the proposed algorithm with a flight experiment in a laboratory condition with wind disturbance similar to outdoor flight.

날갯짓 초소형 비행체에서의 자이로스코프 및 가속도계 센서 동적 특성에 대한 연구

Sensors have become inseparable components in designing control systems, but performance is often degraded by noise from the environment or system. In this paper, the performance of a gyroscope and accelerometer on a flapping wing micro aerial vehicle (FW-MAV) was studied. The effect of a flapping wing on the sensors was observed. The benefit of using a mechanical damper or foam were also compared. The vibration generated by the flapping motion caused the accelerometer to suffer rectification errors, leading to bias or offset shifts in the measurement. Common filtering methods, such as low pass filters and complementary or Kalman filters, are affected by this problem. This study demonstrates that the use of foam can reduce the rectification error significantly.

Experimental Study on the Stiffness and Shape Layout of Flapping Wing

Flapping-wing Micro Air Vehicle (FMAV) is a kind of bionic air vehicle, which looks like natural flying creatures and flies by flapping-wings only. Now, there is an upsurge of relative research about FMAV, and one focus research domain is to develop a flapping-wing with high aerodynamic performance. The wind-tunnel experiment is one of the main research manner, which can be used to test and control many parameters with high accuracy, like force, torque, flapping angle, frequency, power, etc. Based on the wind-tunnel system and inspired by birds, we mainly study the effects of stiffness and shape layout of the flapping wing, and get some conclusions. And this work may set up a good fundamental for further experiment about developing wing with high efficiency.

Computational simulation and free flight validation of body vibration of flapping-wing MAV in forward flight

FWMAVs (Flapping Wing Micro Air Vehicles) turn to be a flexible multi-body dynamic (FMBD) system when the inertia and flexibility of flapping wing are considered. The vibration caused by interaction of unsteady aerodynamics, structural dynamics and multi-body dynamics makes the analysis of aerodynamic and acquisition of equilibrium become full of challenge. In this study, a method coupled three-dimensional CFD (Computational Fluid Dynamics) and CSD (Computational Structural Dynamics) considering FMBD (flexible multi-body dynamics) between flexible wings and body is developed. And a trim algorithm is developed to satisfy three aspects of conditions including convergence of structural deformation and periodic condition of body's vibration in longitudinal direction and conditions of equilibrium. The computational results show that the trim conditions when body's vibration is taken into account are different from that when body's vibration is ignored. The vibration of body mainly increases the aerodynamic drag while having a little effect on lift. When the flight is trimmed, the corresponding flapping frequency increases and angle of attack decreases. In order to validate the method of simulation, the free flight data including the time course of oscillated plunging acceleration and pitch angle is collected based on the steady flight ability of “DOVE” FWMAV. Through comparison, though there is slight discrepancy between computational results and free flight data, it proves that CFD/FMBD method provides a sufficiently good accuracy for the simulation of body vibration of FWMAVs. Based on the proposed and validated model, the influence of various take-off mass on the vibration of body is studied and it indicates that a proper mass ratio between wing to body can suppress the maximum acceleration of vibration to protect the precise sensors and equipment.

Experimental investigation on lift generation of flapping MAV with insect wings of various species

Purpose The purpose of this paper is to experimentally analyze the effect of wing shape of various insects of different species in a flapping micro aerial vehicle (MAV). Design/methodology/approach Six different wings are fabricated for the MAV configuration, which is restricted to the size of 15 cm length and width; all wings have different surface area and constant span length of 6 cm. The force is being measured with the help of a force-sensing resistor (FSR), and the coefficients of lift were calculated and compared. Findings This study shows that the wing “Tipula sp” has better value of lift than other insect wings, except for the negative angle of attacks. The wing “Aeshna multicolor” gives the better values of lift in negative angles of attack. Practical implications This paper lays the foundation for the development of flapping MAVs with the insect wings. This type of wing can be used for spying purpose in the military zone and also can be used to survey remote and dangerous places where humans cannot enter. Originality/value This paper covers all basic insect wing configurations of different species with exact mimics of the veins. As the experimental investigation was carried for different angle of attacks, velocities and flapping frequencies, this paper can be used as reference for future flapping wing MAV developers.

Experimental study of a bio-inspired flapping wing MAV by means of force and PIV measurements

Abstract This study explores the aerodynamic performance of an X-Wing bio-inspired flapping wing micro air vehicle (MAV) underlying clap-and-fling motion by means of force and flow field measurements. Wind tunnel tests were first conducted to identify the operation region of current flapping wing MAV. The effects of flapping frequency and wing flexibility on force generation and power loading were evaluated using a miniature six-component force transducer. Flow visualization in the chordwise wake of the flapping wings is measured by means of phase-lock particle image velocimetry (PIV) measurement, results revealed the shedding behavior of the vertical structures by the wings during clap-and-fling motion showed a momentum surplus. Additionally, the in-ground-effect (IGE) is also examined aiming to understand the aerodynamic characteristics during take-off and landing of flapping wing MAV.

Energy-efficient wing design for flapping wing micro aerial vehicles

Flapping wing micro aerial vehicles (FWMAVs) have attracted more attention during the development of the robotic systems field. The size of the flapping wing plays an important role in the lift force and torque generation based on quasi-steady aerodynamic model. Therefore, it is necessary to study energy-efficient design methods for wings to provide sufficient lift force and torque with minimal energy consumption for hovering flight. In this paper, the sensitive parameters for the lift force and power consumption were first selected based on design of experiment (DOE) and the parameter of the distributed wing stiffness was determined based on experimental data. Design optimization models for three different cases were then built by considering the lift force as one constraint and the energy consumption as the objective function. The combination of subset simulation and the gradient-based optimization was finally used for solving design optimization models, and the corresponding sensitivity analysis was provided.

Longitudinal Modeling and Control of Tailed Flapping-Wings Micro Air Vehicles near Hovering

Compared with the tailless flapping wing micro air vehicle (FMAV), the tailed FMAV has a simpler structure and is easier to control. However, although biplane FMAVs with tails have been used for flight control in practice for a long time, a theoretical model of the tailed FMAV has not previously been established. In this paper, we report modeling of the longitudinal dynamics of a tailed biplane FMAV using the Newton‐Euler equations. In this study, the vehicle was trimmed and linearized near its hovering equilibrium, assuming small disturbances. Then the stability of the hovering FMAV was analyzed with a modal analysis method. A state feedback controller was synthesized to stabilize the disturbance. Finally, we investigated the flight control of the tailed biplane FMAV with different control signals. Our results show that the natural‐motion mode determines the oscillation divergence characteristics of the tailed FMAV, a mode that can be suppressed with the state feedback controller by real‐time modulation of the tail. The tail can also be used to achieve different flight modes with different control‐signal functions. The tailed FMAV cruises in a line when the tail is controlled with a step function and spirals in an elliptical trajectory in the longitudinal plane when the tail is controlled by a sinusoidal function. Our longitudinal‐ dynamics model provides an analytical basis for further dynamic analyses of the tailed FMAV, as well as the corresponding controller synthesis. Moreover, the proposed attitude stabilization and flight control schemes for the vehicle near hovering provide a basis for developing practical uses of the tailed FMAV.

Wing Design, Fabrication, and Analysis for an X-Wing Flapping-Wing Micro Air Vehicle

Flapping-wing Micro Air Vehicles (FW-MAVs), inspired by small insects, have limitless potential to be capable of performing tasks in urban and indoor environments. Through the process of mimicking insect flight, however, there are a lot of challenges for successful flight of these vehicles, which include their design, fabrication, control, and propulsion. To this end, this paper investigates the wing design and fabrication of an X-wing FW-MAV and analyzes its performance in terms of thrust generation. It was designed and developed using a systematic approach. Two pairs of wings were fabricated with a traditional cut-and-glue method and an advanced vacuum mold method. The FW-MAV is equipped with inexpensive and tiny avionics, such as the smallest Arduino controller board, a remote-control receiver, standard sensors, servos, a motor, and a 1-cell battery. Thrust measurement was conducted to compare the performance of different wings at full throttle. Overall, this FW-MAV produces maximum vertical thrust at a pitch angle of 10 degrees. The wing having stiffeners and manufactured using the vacuum mold produces the highest thrust among the tested wings.

Development of a novel flapping wing micro aerial vehicle with elliptical wingtip trajectory

Abstract. This paper describes a novel flapping wing micro air vehicle (FWMAV),which can achieve two active degree of freedom (DOF) movements of flapping and swing, as well as twisting passively. This aircraft has a special “0” figure wingtip motion trajectory with the 140∘ flapping stroke angle. With these characteristics integrated into the simple flapping mechanism, the aerodynamic force is somewhat improved. The model made a balance between the improved aerodynamic performance induced by complicated movements and the increased weight of the extra components in aircraft. In the driven design, Only one micro-motor is employed to drive the wing flapping and swing motion simultaneously forming the prescribed trajectory. The 23 g aircraft could reach the maximum flapping frequency of 11 Hz with the tip-to-tip wingspan of 29 cm.

Fibrous Orientation Effects on the Deformation and Stress of an Insect-like Flapping-wing Micro Aerial Vehicle Based on ACP

This paper examines the effect of different orientation of composite material on the deformation and stress of dragonfly-like flapping-wing micro aerial vehicles (FWMAVs). After billions of years of evolution, insects employing flapping-wing tend to have excellent flight capabilities. To understand the bionic wings will be helpful to design high performance aircrafts. FEM analysis of flapping wing structure simulating dragonfly wings having three layers Epoxy carbon composite material and resin epoxy is glue for adhesive two layers. In the process, the flapping wing model was created in ANSYS Workbench ACP (pre), ACP (post) and then the loading of the flapping wing in each phase will be calculated. Finally, the graphs showing the changes of the maximum deformation displacement and maximum stress can be worked out. It can be known that for the first principle stress, -35° is the best performance because -35° stresses is lowest stress and +35° is the worst performance because this angle is the highest stress. For the second principle stress the -25° is the best performance because -25° have the lowest stress. For the third principle stress, -45° is the worst performance because -45° is the highest stress, +45° is the best performance because here stress is the lowest and 0° is the worst because here stress is the highest. The findings are helpful in answering why insect wings are so impeccable, thus providing possibility of improving the design of flapping wing aerial vehicles. This paper will found why insect wings are impeccable.

Aerodynamic mechanisms in bio‐inspired micro air vehicles: a review in the light of novel compound layouts

Modern designs of micro air vehicles (MAVs) are mostly inspired by nature's flyers, such as hummingbirds and flying insects, which results in the birth of bio-inspired MAVs. The history and recent progress of the aerodynamic mechanisms in bio-inspired MAVs are reviewed in this study, especially focused on those compound layouts using bio-inspired unsteady aerodynamic mechanisms. Several successful bio-mimicking MAVs and the unsteady high lift mechanisms in insect flight are briefly revisited. Four types of the compound layouts, i.e. the fixed/flapping-wing MAV, the flapping rotary wing MAV, the multiple-pair flapping-wing MAV, and the cycloidal rotor MAV are introduced in terms of recent findings on their aerodynamic mechanisms. In the end, future interests in the field of MAVs are suggested. The authors' review can provide solid background knowledge for both future studies on the aerodynamic mechanisms in bio-inspired MAVs and the practical design of a bio-inspired MAV.

Combined co-rotational beam/shell elements for fluid\u2013structure interaction analysis of insect-like flapping wing

Flapping wing micro-air vehicles are biologically inspired by nature flyers, specifically insects and birds. Specifically, insect wings generally consist of veins and membrane components. In this study, a structural analysis considering the vein/membrane components of an insect-like flapping wing is presented. Co-rotational (CR) finite elements are adopted in order to consider the complex wing configuration including both vein and membrane. The CR beam elements with warping degrees of freedom are employed for veins and CR shell elements for the wing membrane. The present structural analysis is verified against the analytical results obtained by an existing software, and it is validated by comparison to existing results from the literature. A fluid–structure interaction analysis is then performed. In the procedure, an aerodynamic analysis based on three-dimensional preconditioned Navier–Stokes equations is employed. Finally, a comparative study with respect to the structural characteristics is conducted. As a result, an efficiency of the present structural analysis is confirmed by comparing with the existing software. It is found that the present FSI results are in good agreement with the existing experimental and numerical results. Moreover, the passive wing twist may have a significant influence on the hover performance.