To better understand the aerodynamic reasons for highly organized movements of flying organisms,the three-flapping wing system in tandem formation was studied numerically in this paper.Different from previous relevant...To better understand the aerodynamic reasons for highly organized movements of flying organisms,the three-flapping wing system in tandem formation was studied numerically in this paper.Different from previous relevant studies on the multiple flapping wings that are equally spaced,this study emphasizes the impact of unequal spacing between individuals on the aerodynamics of each individual wing as well as the whole system.It is found that swapping the distance between the first and second wing with the distance between the second wing and the rearmost wing does not affect the overall aerodynamic performance,but significantly changes the distribution of aerodynamic benefits across each wing.During the whole flapping cycle,three effects are at play.The narrow channel effect and the downwash effect can promote and weaken the wing lift,respectively,while the wake capture effect can boost the thrust.It also shows that these effects could be manipulated by changing the spacing between adjacent wings.These findings provide a novel way for flow control in tandem formation flight and are also inspiring for designing the formation flight of bionic aircraft.展开更多
The development of a tailless Flapping Wing Micro Aerial Vehicle(FWMAV)inspired by the hummingbird is presented in this work.By implementing mechanical simplifications,it is possible to use planar machining technology...The development of a tailless Flapping Wing Micro Aerial Vehicle(FWMAV)inspired by the hummingbird is presented in this work.By implementing mechanical simplifications,it is possible to use planar machining technology for manufacturing of the FWMAV’s body,greatly reducing assembly errors.Traditionally,studies on flapping wing aircraft are limited to open-loop wing kinematics control.In this work,an instantaneous closed-loop wing trajectory tracking control system is introduced to minimize wings’trajectory tracking errors.The control system is based on Field-Oriented Control(FOC)with a loop shaping compensation technique near the flapping frequency.Through frequency analysis,the loop shaping compensator ensures the satisfactory bandwidth and performance for the closed-loop flapping system.To implement the proposed controller,a compact autopilot board integrated with FOC hardware is designed,weighing only 2.5 g.By utilizing precise wing trajectory tracking control,the hummingbird-inspired FWMAV demonstrates superior ability to resist external disturbances and exhibits reduced attitude tracking errors during hovering flight compared to the open-loop wing motion.展开更多
Compared to the traditional flapping-wing structure with single motion mode,a micro servoactuator driven Flapping-Wing Air Vehicle(FWAV)breaks free from the limitations imposed by the motion parameters of the crank-co...Compared to the traditional flapping-wing structure with single motion mode,a micro servoactuator driven Flapping-Wing Air Vehicle(FWAV)breaks free from the limitations imposed by the motion parameters of the crank-connecting rod mechanism.It allows for simultaneous control of wings’position and velocity attitude through pulse width modulation,showcasing unrivaled controllability and promising extensive applications.However,this method of motion control also brings new challenges to the design of the wings’motion parameters.This study seeks to investigate the relationship between the motion parameters of micro servoactuator driven FWAV and its aerodynamic characteristics,then explore a servo control method that can optimize its thrust-producing performance.To achieve this,this paper involves the establishment of Amplitude Loss Model(ALM),Flapping Wing Dynamic Model(FWDM),and Power Load Model(PLM),followed by motion capture experiments,dynamic monitoring experiments,and power monitoring experiments.Experimental results show that the proposed modeling method,which fully considers the amplitude loss effect and advanced twisting effect in flapping-wing motion,can accurately calculate thrust,power,and power load,with prediction errors of less than 10%,5%and 13%,respectively.This high-precision model can effectively optimize motion parameters,allowing for better performance of flapping-wing motion.展开更多
This paper presents a novel modelling method to study the thrust generation mechanism of biplane flapping wings made of thin and highly deformable membrane.Based on the principle of strain energy equivalence,the membr...This paper presents a novel modelling method to study the thrust generation mechanism of biplane flapping wings made of thin and highly deformable membrane.Based on the principle of strain energy equivalence,the membrane structures were modelled by mass-spring systems.The aerodynamic loads were calculated by a simplified quasi-steady aerodynamic model with consideration of the clap-and-fling mechanism.The impact force was introduced into the system when two wing surfaces were in contact.For wing-dynamics simulation problems,convergence analyses were conducted to obtain suitable mesh resolution.To validate the present modelling method,the predicted thrust and required power of a biplane flapping-wing air vehicle were compared with the experimental data.The effect of the forward speed was also analyzed in this paper.It was shown that as the forward speed increases the thrust production efficiency becomes lower together with smaller wing deformation.展开更多
In this study,the aerodynamic performance of flapping wings using a parallel motion was investigated and compared with the insect-like‘‘fan-sweep’’motion,and the effect of adding a slit to the wings was analyzed.F...In this study,the aerodynamic performance of flapping wings using a parallel motion was investigated and compared with the insect-like‘‘fan-sweep’’motion,and the effect of adding a slit to the wings was analyzed.First,numerical simulations were performed to analyze the wing aerodynamics of two flapping motions with equivalent stroke amplitudes over a range of pitching angles based on computational fluid dynamics(CFD).The simulation results indicated that flapping wings with a rapid and short parallel motion achieved better lift and efficiency than those of the fan-sweep motion while maintaining the same aerodynamic characteristics regarding stall delay and leading-edge vortices.For a parallel motion with a pitching angle of 25◦and 100 mm stroke amplitude,the wings generated an average lift of 8.4 gf with a lift-to-drag ratio of 1.06,respectively,which were 1.8%and 26%greater than those of the fan-sweep motion with a corresponding 96◦stroke amplitude.This situation was reversed when the pitching angle and stroke amplitude were increased to 45◦and 144◦for the fan-sweep motion,which was equivalent to the parallel motion with a 150 mm stroke amplitude.The slit effect in the parallel motion was also evaluated,and the CFD results indicated that a slit width of 1 mm(1/50 wing chord)increased the lift of the wing by approximately 27%in the case of the 150 mm stroke amplitude.Further,the slit width slightly influenced the lift and aerodynamic efficiency.展开更多
An immersed-boundary method is used to investigate the flapping wings with different aspect ratios ranging from 1 to 5.The numerical results on wake structures and the performance of the propulsion are given.Unlike th...An immersed-boundary method is used to investigate the flapping wings with different aspect ratios ranging from 1 to 5.The numerical results on wake structures and the performance of the propulsion are given.Unlike the case of the two-dimensional flapping foil,the wing-tip vortices appear for the flow past a three-dimensional flapping wing,which makes the wake vortex structures much different.The results show that the leading edge vortex merges into the trailing edge vortex,connects with the wing tip vortices and then sheds from the wing.A vortex ring forms in the wake,and exhibits different patterns for different foil aspect ratios.Analysis of hydrodynamic performances shows that both thrust coefficient and efficiency of the flapping wing increase with increasing aspect ratio.展开更多
Flying insects are capable of flapping their wings to provide the required power and control forces for flight.A coordinated organizational system including muscles,wings,and control architecture plays a significant r...Flying insects are capable of flapping their wings to provide the required power and control forces for flight.A coordinated organizational system including muscles,wings,and control architecture plays a significant role,which provides the sources of inspiration for designing flapping-wing vehicles.In recent years,due to the development of micro-and meso-scale manufacturing technologies,advances in components technologies have directly led to a progress of smaller Flapping-Wing Nano Air Vehicles(FWNAVs)around gram and sub-gram scales,and these air vehicles have gradually acquired insect-like locomotive strategies and capabilities.This paper will present a selective review of components technologies for ultra-lightweight flapping-wing nano air vehicles under 3 g,which covers the novel propulsion methods such as artificial muscles,flight control mechanisms,and the design paradigms of the insect-inspired wings,with a special focus on the development of the driving technologies based on artificial muscles and the progress of the biomimetic wings.The challenges involved in constructing such small flapping-wing air vehicles and recommendations for several possible future directions in terms of component technology enhancements and overall vehicle performance are also discussed in this paper.This review will provide the essential guidelines and the insights for designing a flapping-wing nano air vehicle with higher performance.展开更多
Flapping-wing flight, as the distinctive flight method retained by natural flying creatures, contains profound aerodynamic principles and brings great inspirations and encouragements to drone developers. Though some i...Flapping-wing flight, as the distinctive flight method retained by natural flying creatures, contains profound aerodynamic principles and brings great inspirations and encouragements to drone developers. Though some ingenious flapping-wing robots have been designed during the past two decades, development and application of autonomous flapping-wing robots are less successful and still require further research. Here, we report the development of a servo-driven bird-like flapping-wing robot named USTBird-I and its application in autonomous airdrop.Inspired by birds, a camber structure and a dihedral angle adjustment mechanism are introduced into the airfoil design and motion control of the wings, respectively. Computational fluid dynamics simulations and actual flight tests show that this bionic design can significantly improve the gliding performance of the robot, which is beneficial to the execution of the airdrop mission.Finally, a vision-based airdrop experiment has been successfully implemented on USTBird-I, which is the first demonstration of a bird-like flapping-wing robot conducting an outdoor airdrop mission.展开更多
The 3D model of flapping wing mechanism and veins is constructed in 3D computer aided design (CAD) software UG.Then the co-simulation model is established by using multibody dynamics software ADAMS and MATLAB.The vali...The 3D model of flapping wing mechanism and veins is constructed in 3D computer aided design (CAD) software UG.Then the co-simulation model is established by using multibody dynamics software ADAMS and MATLAB.The validation of this co-simulation model is verified by comparing the simulation results with final experiments.The simulation results and experiments reveal that the relation between flapping frequency and driving voltage of motor is approximately linear under various wingspans.The variance of flapping frequency among different wingspans augments gradually with increasing voltage.Furthermore,the simulation results suggest that flapping frequency is sensitive to wingspan and decreases with increasing wingspan of veins,and the relation between flapping frequency and moment of inertia of veins is also approximately linear for various voltages.展开更多
Most flapping-wing aircraft wings use a single degree of freedom to generate lift and thrust by flapping up and down,while relying on the tail control surfaces to manage attitude.However,these aircraft have certain li...Most flapping-wing aircraft wings use a single degree of freedom to generate lift and thrust by flapping up and down,while relying on the tail control surfaces to manage attitude.However,these aircraft have certain limitations,such as poor accuracy in attitude control and inadequate roll control capabilities.This paper presents a design for an active torsional mechanism at the wing's trailing edge,which enables differential variations in the pitch angle of the left and right wings during flapping.This simple mechanical form significantly enhances the aircraft's roll control capacity.The experimental verification of this mechanism was conducted in a wind tunnel using the RoboEagle flapping-wing aerial vehicle that we developed.The study investigated the effects of the control strategy on lift,thrust,and roll moment during flapping flight.Additionally,the impact of roll control on roll moment was examined under various wind speeds,flapping frequencies,angles of attack,and wing flexibility.Furthermore,several rolling maneuver flight tests were performed to evaluate the agility of RoboEagle,utilizing both the elevon control strategy and the new roll control strategy.The results demonstrated that the new roll control strategy effectively enhances the roll control capability,thereby improving the attitude control capabilities of the flapping-wing aircraft in complex wind field environments.This conclusion is supported by a comparison of the control time,maximum roll angle,average roll angular velocity,and other relevant parameters between the two control strategies under identical roll control input.展开更多
Flapping-Wing Micro Air Vehicles(FMAVs)are compact and agile,capable of accessing narrow spaces that conventional vehicles struggle to reach,such as ruins,caves,or the interiors of complex structures,making them ideal...Flapping-Wing Micro Air Vehicles(FMAVs)are compact and agile,capable of accessing narrow spaces that conventional vehicles struggle to reach,such as ruins,caves,or the interiors of complex structures,making them ideal tools for reconnaissance and rescue missions.1 However,the operation of FMAVs relies on coordinating multiple forces with different scaling effects,posing challenges to miniaturization design.展开更多
Modeling the dynamics of flapping wing aerial vehicle is challenging due to the complexity of aerodynamic effects and mechanical structures.The aim of this work is to develop an accurate dynamics model of flapping win...Modeling the dynamics of flapping wing aerial vehicle is challenging due to the complexity of aerodynamic effects and mechanical structures.The aim of this work is to develop an accurate dynamics model of flapping wing aerial vehicle based on real flight data.We propose a modeling framework that combines rigid body dynamics with a neural network to predict aerodynamic effects.By incorporating the concept of flapping phase,we significantly enhance the network’s ability to analyze transient aerodynamic behavior.We design and utilize a phase-functioned neural network structure for aerodynamic predictions and train the network using real flight data.Evaluation results show that the network can predict aerodynamic effects and demonstrate clear physical significance.We verify that the framework can be used for dynamic propagation and is expected to be utilized for building simulators for flapping wing aerial vehicles.展开更多
Throughout the previous studies,none of them are involved in analysing the downwash flow effect on the control surface of the Flapping Wing Rotor(FWR).An overset CFD numerical model is built up and validated to study ...Throughout the previous studies,none of them are involved in analysing the downwash flow effect on the control surface of the Flapping Wing Rotor(FWR).An overset CFD numerical model is built up and validated to study the downwash flow’s effect on the stability of the FWR.After simulation,a cone like self-lock region which acts as the critical condition determining the stability of FWR is found.Only when the flow’s resultant velocity acting on the control surface lies in the stable region,the FWR can keep stable.The size of the cone like self-lock stable region can be enlarged by increasing the maximum feasible deflection angle constrained by mechanical design or enhancing the equivalent downwash flow velocity.Among all the simulated cases,when J=2.67(f=5 Hz,■=5 r/s),the largest average equivalent downwash flow velocities are found.On the other hand,the recovery torque could be enhanced due to the increase of the arm of the lateral force.According to these simulation results,a 43 g FWR model with two control surfaces and two stabilizers is then designed.A series of flight tests is then conducted to help confirm the conclusion of the mechanism research in this work.Overall,this study points out several strategies to increase the flight stability of the FWR and finally realizes the stable climb flight and mild descent flight of the FWR.展开更多
A theoretical modeling approach as well as an unsteady analytical method is used to study aerodynamic characteristics of wing flapping with asymmetric stroke-cycles in connection with an oblique stroke plane during in...A theoretical modeling approach as well as an unsteady analytical method is used to study aerodynamic characteristics of wing flapping with asymmetric stroke-cycles in connection with an oblique stroke plane during insect forward flight. It is revealed that the aerodynamic asymmetry between the downstroke and the upstroke due to stroke-asymmetrical flapping is a key to understand the flow physics of generation and modulation of the lift and the thrust. Predicted results for examples of given kinematics validate more specifically some viewpoints that the wing lift is more easily produced when the forward speed is higher and the thrust is harder, and the lift and the thrust are generated mainly during downstroke and upstroke, respectively. The effects of three controlling parameters, i.e. the angles of tilted stroke plane, the different downstroke duration ratios, and the different angles of attack in both down- and up-stroke, are further discussed. It is found that larger oblique angles of stroke planes generate larger thrust but smaller lift; larger downstroke duration ratios lead to larger thrust, while making little change in lift and input aerodynamic power; and again, a small increase of the angle of attack in downstroke or upstroke may cause remarkable changes in aerodynamic performance in the relevant stroke.展开更多
The application of biomimetics in the development of unmanned-aerial-vehicles （UAV） has advanced to an exceptionally small scale of nano-aerial-vehicles （NAV）, which has surpassed its immediate predecessor of micr...The application of biomimetics in the development of unmanned-aerial-vehicles （UAV） has advanced to an exceptionally small scale of nano-aerial-vehicles （NAV）, which has surpassed its immediate predecessor of micro-aerial-vehicles （MAV）, leaving a vast range of development possi- bilities that MAVs have to offer. Because of the prompt advancement into the NAV research devel- opment, the true potential and challenges presented by MAV development were never solved, understood, and truly uncovered, especially under the influence of transition and low Reynolds number flow characteristics. This paper reviews a part of previous MAV research developments which are deemed important of notification; kinematics, membranes, and flapping mechanisms ranges from small birds to big insects, which resides within the transition and low Reynolds number regimes. This paper also reviews the possibility of applying a piezoelectric transmission used to pro- duce NAV flapping wing motion and mounted on a MAV, replacing the conventional motorized flapping wing transmission. Findings suggest that limited work has been done for MAVs matching these criteria. The preferred research approach has seen bias towards numerical analysis as compared to experimental analysis.展开更多
A three-wing Flapping Wing Rotor Micro Aerial Vehicle(FWR-MAV)which can perform controlled flight is introduced and an experimental study on this vehicle is presented.A mechanically driven flapping rotary mechanism is...A three-wing Flapping Wing Rotor Micro Aerial Vehicle(FWR-MAV)which can perform controlled flight is introduced and an experimental study on this vehicle is presented.A mechanically driven flapping rotary mechanism is designed to drive the three flapping wings and generate lift,and control mechanisms are designed to control the pose of the FWR-MAV.A flight control board for attitude control with robust onboard attitude estimation and a control algorithm is also developed to perform stable hovering flight and forward flight.A series of flight tests was conducted,with hovering flight and forward flight tests performed to optimize the control parameters and assess the performance of the FWR-MAV.The hovering flight test shows the ability of the FWR-MAV to counteract the moment generated by rotary motion and maintain the attitude of the FWR-MAV in space;the experiment of forward flight shows that the FWR-MAV can track the desired attitude.展开更多
The analysis of the passive rotation feature of a micro Flapping Rotary Wing（FRW）applicable for Micro Air Vehicle（MAV） design is presented in this paper. The dynamics of the wing and its influence on aerodynamic p...The analysis of the passive rotation feature of a micro Flapping Rotary Wing（FRW）applicable for Micro Air Vehicle（MAV） design is presented in this paper. The dynamics of the wing and its influence on aerodynamic performance of FRW is studied at low Reynolds number（~10~3）.The FRW is modeled as a simplified system of three rigid bodies： a rotary base with two flapping wings. The multibody dynamic theory is employed to derive the motion equations for FRW. A quasi-steady aerodynamic model is utilized for the calculation of the aerodynamic forces and moments. The dynamic motion process and the effects of the kinematics of wings on the dynamic rotational equilibrium of FWR and the aerodynamic performances are studied. The results show that the passive rotation motion of the wings is a continuous dynamic process which converges into an equilibrium rotary velocity due to the interaction between aerodynamic thrust, drag force and wing inertia. This causes a unique dynamic time-lag phenomena of lift generation for FRW, unlike the normal flapping wing flight vehicle driven by its own motor to actively rotate its wings. The analysis also shows that in order to acquire a high positive lift generation with high power efficiency and small dynamic time-lag, a relative high mid-up stroke angle within 7–15° and low mid-down stroke angle within -40° to -35° are necessary. The results provide a quantified guidance for design option of FRW together with the optimal kinematics of motion according to flight performance requirement.展开更多
Most insects and hummingbirds can generate lift during both upstroke and downstroke with a nearly horizontal flapping stroke plane,and perform precise hovering flight.Further,most birds can utilize tails and muscles i...Most insects and hummingbirds can generate lift during both upstroke and downstroke with a nearly horizontal flapping stroke plane,and perform precise hovering flight.Further,most birds can utilize tails and muscles in wings to actively control the flight performance,while insects control their flight with muscles based on wing root along with wing’s passive deformation.Based on the above flight principles of birds and insects,Flapping Wing Micro Air Vehicles(FWMAVs)are classified as either bird-inspired or insect-inspired FWMAVs.In this review,the research achievements on mechanisms of insect-inspired,hoverable FWMAVs over the last ten years(2011-2020)are provided.We also provide the definition,function,research status and development prospect of hoverable FWMAVs.Then discuss it from three aspects:bio-inspiration,motor-driving mechanisms and intelligent actuator-driving mechanisms.Following this,research groups involved in insect-inspired,hoverable FWMAV research and their major achievements are summarized and classified in tables.Problems,trends and challenges about the mechanism are compiled and presented.Finally,this paper presents conclusions about research on mechanical structure,and the future is discussed to enable further research interests.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.12172276)Shaanxi key research and development program(Grant No.2022ZDLGY02-07).
文摘To better understand the aerodynamic reasons for highly organized movements of flying organisms,the three-flapping wing system in tandem formation was studied numerically in this paper.Different from previous relevant studies on the multiple flapping wings that are equally spaced,this study emphasizes the impact of unequal spacing between individuals on the aerodynamics of each individual wing as well as the whole system.It is found that swapping the distance between the first and second wing with the distance between the second wing and the rearmost wing does not affect the overall aerodynamic performance,but significantly changes the distribution of aerodynamic benefits across each wing.During the whole flapping cycle,three effects are at play.The narrow channel effect and the downwash effect can promote and weaken the wing lift,respectively,while the wake capture effect can boost the thrust.It also shows that these effects could be manipulated by changing the spacing between adjacent wings.These findings provide a novel way for flow control in tandem formation flight and are also inspiring for designing the formation flight of bionic aircraft.
基金support by the National Natural Science Foundation of China(No.62073217,No.61871266)the Fund of the Ministry of Education of the People’s Republic of China(6141A02022607,6141A020227)the Fund of the Professional Technical Service Platform of Shanghai(19DZ2291103).
文摘The development of a tailless Flapping Wing Micro Aerial Vehicle(FWMAV)inspired by the hummingbird is presented in this work.By implementing mechanical simplifications,it is possible to use planar machining technology for manufacturing of the FWMAV’s body,greatly reducing assembly errors.Traditionally,studies on flapping wing aircraft are limited to open-loop wing kinematics control.In this work,an instantaneous closed-loop wing trajectory tracking control system is introduced to minimize wings’trajectory tracking errors.The control system is based on Field-Oriented Control(FOC)with a loop shaping compensation technique near the flapping frequency.Through frequency analysis,the loop shaping compensator ensures the satisfactory bandwidth and performance for the closed-loop flapping system.To implement the proposed controller,a compact autopilot board integrated with FOC hardware is designed,weighing only 2.5 g.By utilizing precise wing trajectory tracking control,the hummingbird-inspired FWMAV demonstrates superior ability to resist external disturbances and exhibits reduced attitude tracking errors during hovering flight compared to the open-loop wing motion.
基金supported by the Foundation for Innovative Research Groups of the National Natural Science Foundation of China(No.51521003)the Natural Science Foundation of Heilongjiang Province(No.ZD2023E002)+1 种基金HIT Wuhu Robot Technology Research Institute(No.HIT-CXY-CMP2-RVJDT-21-01)the Open Fund for Laboratory of Aerospace Servo Actuation and Transmission(No.LASAT-2022-A01-02).
文摘Compared to the traditional flapping-wing structure with single motion mode,a micro servoactuator driven Flapping-Wing Air Vehicle(FWAV)breaks free from the limitations imposed by the motion parameters of the crank-connecting rod mechanism.It allows for simultaneous control of wings’position and velocity attitude through pulse width modulation,showcasing unrivaled controllability and promising extensive applications.However,this method of motion control also brings new challenges to the design of the wings’motion parameters.This study seeks to investigate the relationship between the motion parameters of micro servoactuator driven FWAV and its aerodynamic characteristics,then explore a servo control method that can optimize its thrust-producing performance.To achieve this,this paper involves the establishment of Amplitude Loss Model(ALM),Flapping Wing Dynamic Model(FWDM),and Power Load Model(PLM),followed by motion capture experiments,dynamic monitoring experiments,and power monitoring experiments.Experimental results show that the proposed modeling method,which fully considers the amplitude loss effect and advanced twisting effect in flapping-wing motion,can accurately calculate thrust,power,and power load,with prediction errors of less than 10%,5%and 13%,respectively.This high-precision model can effectively optimize motion parameters,allowing for better performance of flapping-wing motion.
基金funded by Vietnam National Foundation for Science and Technology Development(NAFOSTED)(Grant No.107.01-2021.39).
文摘This paper presents a novel modelling method to study the thrust generation mechanism of biplane flapping wings made of thin and highly deformable membrane.Based on the principle of strain energy equivalence,the membrane structures were modelled by mass-spring systems.The aerodynamic loads were calculated by a simplified quasi-steady aerodynamic model with consideration of the clap-and-fling mechanism.The impact force was introduced into the system when two wing surfaces were in contact.For wing-dynamics simulation problems,convergence analyses were conducted to obtain suitable mesh resolution.To validate the present modelling method,the predicted thrust and required power of a biplane flapping-wing air vehicle were compared with the experimental data.The effect of the forward speed was also analyzed in this paper.It was shown that as the forward speed increases the thrust production efficiency becomes lower together with smaller wing deformation.
基金funding organizations in China:the National Key Research and Development Program of China(Grant No.2018YFB1305400)the National Natural Science Foundation of China(Grant Nos.62173212 and 11972079).
文摘In this study,the aerodynamic performance of flapping wings using a parallel motion was investigated and compared with the insect-like‘‘fan-sweep’’motion,and the effect of adding a slit to the wings was analyzed.First,numerical simulations were performed to analyze the wing aerodynamics of two flapping motions with equivalent stroke amplitudes over a range of pitching angles based on computational fluid dynamics(CFD).The simulation results indicated that flapping wings with a rapid and short parallel motion achieved better lift and efficiency than those of the fan-sweep motion while maintaining the same aerodynamic characteristics regarding stall delay and leading-edge vortices.For a parallel motion with a pitching angle of 25◦and 100 mm stroke amplitude,the wings generated an average lift of 8.4 gf with a lift-to-drag ratio of 1.06,respectively,which were 1.8%and 26%greater than those of the fan-sweep motion with a corresponding 96◦stroke amplitude.This situation was reversed when the pitching angle and stroke amplitude were increased to 45◦and 144◦for the fan-sweep motion,which was equivalent to the parallel motion with a 150 mm stroke amplitude.The slit effect in the parallel motion was also evaluated,and the CFD results indicated that a slit width of 1 mm(1/50 wing chord)increased the lift of the wing by approximately 27%in the case of the 150 mm stroke amplitude.Further,the slit width slightly influenced the lift and aerodynamic efficiency.
基金supported by the Doctoral Research Foundation of Chinese Universities (Grant No. 20070335066)the National Natural Science Foundation of China (Grant Nos. 50735004, 10802075)
文摘An immersed-boundary method is used to investigate the flapping wings with different aspect ratios ranging from 1 to 5.The numerical results on wake structures and the performance of the propulsion are given.Unlike the case of the two-dimensional flapping foil,the wing-tip vortices appear for the flow past a three-dimensional flapping wing,which makes the wake vortex structures much different.The results show that the leading edge vortex merges into the trailing edge vortex,connects with the wing tip vortices and then sheds from the wing.A vortex ring forms in the wake,and exhibits different patterns for different foil aspect ratios.Analysis of hydrodynamic performances shows that both thrust coefficient and efficiency of the flapping wing increase with increasing aspect ratio.
基金supported by the National Natural Science Foundation of China(Nos.52175277,51905431).
文摘Flying insects are capable of flapping their wings to provide the required power and control forces for flight.A coordinated organizational system including muscles,wings,and control architecture plays a significant role,which provides the sources of inspiration for designing flapping-wing vehicles.In recent years,due to the development of micro-and meso-scale manufacturing technologies,advances in components technologies have directly led to a progress of smaller Flapping-Wing Nano Air Vehicles(FWNAVs)around gram and sub-gram scales,and these air vehicles have gradually acquired insect-like locomotive strategies and capabilities.This paper will present a selective review of components technologies for ultra-lightweight flapping-wing nano air vehicles under 3 g,which covers the novel propulsion methods such as artificial muscles,flight control mechanisms,and the design paradigms of the insect-inspired wings,with a special focus on the development of the driving technologies based on artificial muscles and the progress of the biomimetic wings.The challenges involved in constructing such small flapping-wing air vehicles and recommendations for several possible future directions in terms of component technology enhancements and overall vehicle performance are also discussed in this paper.This review will provide the essential guidelines and the insights for designing a flapping-wing nano air vehicle with higher performance.
基金supported in part by the National Natural Science Foundation of China(62225304,61933001,61921004,62173031)the Beijing Municipal Natural Science Foundation(JQ20026)+1 种基金the Beijing Top Discipline for Artificial Intelligent Science and Engineering,University of Science and Technology Beijing。
文摘Flapping-wing flight, as the distinctive flight method retained by natural flying creatures, contains profound aerodynamic principles and brings great inspirations and encouragements to drone developers. Though some ingenious flapping-wing robots have been designed during the past two decades, development and application of autonomous flapping-wing robots are less successful and still require further research. Here, we report the development of a servo-driven bird-like flapping-wing robot named USTBird-I and its application in autonomous airdrop.Inspired by birds, a camber structure and a dihedral angle adjustment mechanism are introduced into the airfoil design and motion control of the wings, respectively. Computational fluid dynamics simulations and actual flight tests show that this bionic design can significantly improve the gliding performance of the robot, which is beneficial to the execution of the airdrop mission.Finally, a vision-based airdrop experiment has been successfully implemented on USTBird-I, which is the first demonstration of a bird-like flapping-wing robot conducting an outdoor airdrop mission.
基金the National Natural Science Foundationof China(No.60375033)
文摘The 3D model of flapping wing mechanism and veins is constructed in 3D computer aided design (CAD) software UG.Then the co-simulation model is established by using multibody dynamics software ADAMS and MATLAB.The validation of this co-simulation model is verified by comparing the simulation results with final experiments.The simulation results and experiments reveal that the relation between flapping frequency and driving voltage of motor is approximately linear under various wingspans.The variance of flapping frequency among different wingspans augments gradually with increasing voltage.Furthermore,the simulation results suggest that flapping frequency is sensitive to wingspan and decreases with increasing wingspan of veins,and the relation between flapping frequency and moment of inertia of veins is also approximately linear for various voltages.
基金supported by National Natural Science Foundation of China under Grants No.52175277 and 12272318ND Basic Research Funds under Grants G2022WD,Key R&D Program in Shaanxi Province of China under Grant No.2023-YBGY-372.
文摘Most flapping-wing aircraft wings use a single degree of freedom to generate lift and thrust by flapping up and down,while relying on the tail control surfaces to manage attitude.However,these aircraft have certain limitations,such as poor accuracy in attitude control and inadequate roll control capabilities.This paper presents a design for an active torsional mechanism at the wing's trailing edge,which enables differential variations in the pitch angle of the left and right wings during flapping.This simple mechanical form significantly enhances the aircraft's roll control capacity.The experimental verification of this mechanism was conducted in a wind tunnel using the RoboEagle flapping-wing aerial vehicle that we developed.The study investigated the effects of the control strategy on lift,thrust,and roll moment during flapping flight.Additionally,the impact of roll control on roll moment was examined under various wind speeds,flapping frequencies,angles of attack,and wing flexibility.Furthermore,several rolling maneuver flight tests were performed to evaluate the agility of RoboEagle,utilizing both the elevon control strategy and the new roll control strategy.The results demonstrated that the new roll control strategy effectively enhances the roll control capability,thereby improving the attitude control capabilities of the flapping-wing aircraft in complex wind field environments.This conclusion is supported by a comparison of the control time,maximum roll angle,average roll angular velocity,and other relevant parameters between the two control strategies under identical roll control input.
基金supported by the Scientific Research Innovation Capability Support Project for Young Faculty,China(No.ZYGXQNJSKYCXNLZCXM-D1)the National Natural Science Foundation of China(No.52272384).
文摘Flapping-Wing Micro Air Vehicles(FMAVs)are compact and agile,capable of accessing narrow spaces that conventional vehicles struggle to reach,such as ruins,caves,or the interiors of complex structures,making them ideal tools for reconnaissance and rescue missions.1 However,the operation of FMAVs relies on coordinating multiple forces with different scaling effects,posing challenges to miniaturization design.
基金supported by National Natural Science Foundation of China under Grant No.62236007the specialized research projects of Huanjiang Laboratory.
文摘Modeling the dynamics of flapping wing aerial vehicle is challenging due to the complexity of aerodynamic effects and mechanical structures.The aim of this work is to develop an accurate dynamics model of flapping wing aerial vehicle based on real flight data.We propose a modeling framework that combines rigid body dynamics with a neural network to predict aerodynamic effects.By incorporating the concept of flapping phase,we significantly enhance the network’s ability to analyze transient aerodynamic behavior.We design and utilize a phase-functioned neural network structure for aerodynamic predictions and train the network using real flight data.Evaluation results show that the network can predict aerodynamic effects and demonstrate clear physical significance.We verify that the framework can be used for dynamic propagation and is expected to be utilized for building simulators for flapping wing aerial vehicles.
基金supported by the following funding organizations in China:National Natural Science Foundation of China(Grant No.52375116 and Grant No.52105285)the Aeronautical Science Foundation of China(Grant No.ASFC-20230023052001)+3 种基金China Postdoctoral Science Foundation(Grant No.2024M754237)National Key Research and Development Program of China(2024YFB470920001)Science and Technology Plan Project of Wenzhou Municipality(Grant No.ZG2024001)Basic Public Welfare Research Program of Wenzhou(Grant No.G2023046).
文摘Throughout the previous studies,none of them are involved in analysing the downwash flow effect on the control surface of the Flapping Wing Rotor(FWR).An overset CFD numerical model is built up and validated to study the downwash flow’s effect on the stability of the FWR.After simulation,a cone like self-lock region which acts as the critical condition determining the stability of FWR is found.Only when the flow’s resultant velocity acting on the control surface lies in the stable region,the FWR can keep stable.The size of the cone like self-lock stable region can be enlarged by increasing the maximum feasible deflection angle constrained by mechanical design or enhancing the equivalent downwash flow velocity.Among all the simulated cases,when J=2.67(f=5 Hz,■=5 r/s),the largest average equivalent downwash flow velocities are found.On the other hand,the recovery torque could be enhanced due to the increase of the arm of the lateral force.According to these simulation results,a 43 g FWR model with two control surfaces and two stabilizers is then designed.A series of flight tests is then conducted to help confirm the conclusion of the mechanism research in this work.Overall,this study points out several strategies to increase the flight stability of the FWR and finally realizes the stable climb flight and mild descent flight of the FWR.
基金The project supported by the National Natural Science Foundation of China(10072066,90305009) the Chinese Academy of Sciences(KJCX-SW-L04,KJCX2-SW-L2)
文摘A theoretical modeling approach as well as an unsteady analytical method is used to study aerodynamic characteristics of wing flapping with asymmetric stroke-cycles in connection with an oblique stroke plane during insect forward flight. It is revealed that the aerodynamic asymmetry between the downstroke and the upstroke due to stroke-asymmetrical flapping is a key to understand the flow physics of generation and modulation of the lift and the thrust. Predicted results for examples of given kinematics validate more specifically some viewpoints that the wing lift is more easily produced when the forward speed is higher and the thrust is harder, and the lift and the thrust are generated mainly during downstroke and upstroke, respectively. The effects of three controlling parameters, i.e. the angles of tilted stroke plane, the different downstroke duration ratios, and the different angles of attack in both down- and up-stroke, are further discussed. It is found that larger oblique angles of stroke planes generate larger thrust but smaller lift; larger downstroke duration ratios lead to larger thrust, while making little change in lift and input aerodynamic power; and again, a small increase of the angle of attack in downstroke or upstroke may cause remarkable changes in aerodynamic performance in the relevant stroke.
文摘The application of biomimetics in the development of unmanned-aerial-vehicles （UAV） has advanced to an exceptionally small scale of nano-aerial-vehicles （NAV）, which has surpassed its immediate predecessor of micro-aerial-vehicles （MAV）, leaving a vast range of development possi- bilities that MAVs have to offer. Because of the prompt advancement into the NAV research devel- opment, the true potential and challenges presented by MAV development were never solved, understood, and truly uncovered, especially under the influence of transition and low Reynolds number flow characteristics. This paper reviews a part of previous MAV research developments which are deemed important of notification; kinematics, membranes, and flapping mechanisms ranges from small birds to big insects, which resides within the transition and low Reynolds number regimes. This paper also reviews the possibility of applying a piezoelectric transmission used to pro- duce NAV flapping wing motion and mounted on a MAV, replacing the conventional motorized flapping wing transmission. Findings suggest that limited work has been done for MAVs matching these criteria. The preferred research approach has seen bias towards numerical analysis as compared to experimental analysis.
基金supported by the National Natural Science Foundation of China(No.:11572023)。
文摘A three-wing Flapping Wing Rotor Micro Aerial Vehicle(FWR-MAV)which can perform controlled flight is introduced and an experimental study on this vehicle is presented.A mechanically driven flapping rotary mechanism is designed to drive the three flapping wings and generate lift,and control mechanisms are designed to control the pose of the FWR-MAV.A flight control board for attitude control with robust onboard attitude estimation and a control algorithm is also developed to perform stable hovering flight and forward flight.A series of flight tests was conducted,with hovering flight and forward flight tests performed to optimize the control parameters and assess the performance of the FWR-MAV.The hovering flight test shows the ability of the FWR-MAV to counteract the moment generated by rotary motion and maintain the attitude of the FWR-MAV in space;the experiment of forward flight shows that the FWR-MAV can track the desired attitude.
文摘The analysis of the passive rotation feature of a micro Flapping Rotary Wing（FRW）applicable for Micro Air Vehicle（MAV） design is presented in this paper. The dynamics of the wing and its influence on aerodynamic performance of FRW is studied at low Reynolds number（~10~3）.The FRW is modeled as a simplified system of three rigid bodies： a rotary base with two flapping wings. The multibody dynamic theory is employed to derive the motion equations for FRW. A quasi-steady aerodynamic model is utilized for the calculation of the aerodynamic forces and moments. The dynamic motion process and the effects of the kinematics of wings on the dynamic rotational equilibrium of FWR and the aerodynamic performances are studied. The results show that the passive rotation motion of the wings is a continuous dynamic process which converges into an equilibrium rotary velocity due to the interaction between aerodynamic thrust, drag force and wing inertia. This causes a unique dynamic time-lag phenomena of lift generation for FRW, unlike the normal flapping wing flight vehicle driven by its own motor to actively rotate its wings. The analysis also shows that in order to acquire a high positive lift generation with high power efficiency and small dynamic time-lag, a relative high mid-up stroke angle within 7–15° and low mid-down stroke angle within -40° to -35° are necessary. The results provide a quantified guidance for design option of FRW together with the optimal kinematics of motion according to flight performance requirement.
文摘Most insects and hummingbirds can generate lift during both upstroke and downstroke with a nearly horizontal flapping stroke plane,and perform precise hovering flight.Further,most birds can utilize tails and muscles in wings to actively control the flight performance,while insects control their flight with muscles based on wing root along with wing’s passive deformation.Based on the above flight principles of birds and insects,Flapping Wing Micro Air Vehicles(FWMAVs)are classified as either bird-inspired or insect-inspired FWMAVs.In this review,the research achievements on mechanisms of insect-inspired,hoverable FWMAVs over the last ten years(2011-2020)are provided.We also provide the definition,function,research status and development prospect of hoverable FWMAVs.Then discuss it from three aspects:bio-inspiration,motor-driving mechanisms and intelligent actuator-driving mechanisms.Following this,research groups involved in insect-inspired,hoverable FWMAV research and their major achievements are summarized and classified in tables.Problems,trends and challenges about the mechanism are compiled and presented.Finally,this paper presents conclusions about research on mechanical structure,and the future is discussed to enable further research interests.
