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
This paper is based on a previously developed bio-inspired Flapping Wing Aerial Vehicle(FWAV),RoboFalcon,which can fly with a morphing-coupled flapping pattern.In this paper,a simple flapping stroke control system bas...This paper is based on a previously developed bio-inspired Flapping Wing Aerial Vehicle(FWAV),RoboFalcon,which can fly with a morphing-coupled flapping pattern.In this paper,a simple flapping stroke control system based on Hall effect sensors is designed and applied,which is capable of assigning different up-and down-stroke speeds for the RoboFalcon platform to achieve an adjustable downstroke ratio.The aerodynamic and power characteristics of the morphing-coupled flapping pattern and the conventional flapping pattern with varying downstroke ratios are measured through a wind tunnel experiment,and the corresponding aerodynamic models are developed and analyzed by the nonlinear least squares method.The relatively low power consumption of the slow-downstroke mode of this vehicle is verified through outdoor flight tests.The results of wind tunnel experiments and flight tests indicate that increased downstroke duration can improve aerodynamic and power performance for the RoboFalcon platform.展开更多
Birds and bats retract and stretch their wings dynamically during each flap in level flights, implying intriguing mechanisms for the aerodynamic performance improvement of flapping wings. A numerical investigation int...Birds and bats retract and stretch their wings dynamically during each flap in level flights, implying intriguing mechanisms for the aerodynamic performance improvement of flapping wings. A numerical investigation into the aerodynamic effects of such bio-inspired concept in forward flights has been performed based on a three-dimensional wing in plunging motion and a twosection wing in flapping motion. The currently considered Reynolds number and Strouhal number are Re=1.5×10^(5) and St=0.3, respectively. During the research, the mean angle of attack is varied in relatively wide ranges to achieve lift-thrust interconversion for the wings. The conclusive results show that dynamical spanwise retraction and stretch has induced three absolutely desirable scenarios for the oscillating wings in forward flights, namely producing more lift and consuming less power for a given thrust generation, producing more thrust and consuming less power for a given lift generation, and producing more lift and more thrust while consuming less power. Furthermore,the morphing wings have alleviated periodical aerodynamic load fluctuations compared with the non-morphing baseline. The mechanism of the aerodynamic effects of the bionic morphing mode is analyzed with the aid of field visualization. The current article is the first to reveal the absolute advantages of the bionic spanwise morphing. Hopefully, it may help comprehend the behaviors of natural fliers and provide inspirations for performance enhancement of micro artificial flappingwing vehicles.展开更多
Insects usually fly by passively rotating wings,which has been applied to the design of flapping-wing Micro-Air Vehicles(MAVs)to reduce mechanical complexity.In this paper,a robotic passive rotating-wing model is desi...Insects usually fly by passively rotating wings,which has been applied to the design of flapping-wing Micro-Air Vehicles(MAVs)to reduce mechanical complexity.In this paper,a robotic passive rotating-wing model is designed to investigate wing kinematics and lift generation,which are measured by a high-speed camera and a force transducer,respectively.In addition,flow fields are measured using the Particle Image Velocimetry(PIV).Experimental results demonstrate that passive rotating motion has a coordinative relationship with actively stroking motion.As the stroke amplitude or frequency increases,the rotating amplitude is enlarged.To characterize the active stroking motion,a driving Reynolds number Redrivingis defined,which varies from 68 to 366 in this study.Moving the gravity center of the wing towards trailing ed ge induces the increase of additional torque M,which decreases the wing rotating amplitude and promotes the advance of wing rotation.We find that the timing of wing rotation is gradually delayed and the mean lift coefficient C^(-)_(L)monotonously decreases as Redrivingincreases.By increasing the additional torque M,C^(-)_(L)is slightly improved and approaches to the lift coefficient of a real fruit fly at driving Re approximately equal to 230.The instantaneous lifts combined with the vortical structures further demonstrate that the lift generation associated with wing rotation is mainly attributed to the growth of the LeadingEdge Vortex(LEV)and the passive wake capture mechanism.Passive wake capture is influenced by LEV,reversal stroke motion and wing additional torque together,which can only maintain the lift at a high level for a considerable period.The high-lift generation mechanisms of flapping and passive rotating flight could shed light on the simplified design of MAVs and the improvement of their aerodynamic performance.展开更多
Flapping Wing Micro Aerial Vehicles(FWMAVs)have caused great concern in various fields because of their high efficiency and maneuverability.Flapping wing motion is a very important factor that affects the performance ...Flapping Wing Micro Aerial Vehicles(FWMAVs)have caused great concern in various fields because of their high efficiency and maneuverability.Flapping wing motion is a very important factor that affects the performance of the aircraft,and previous works have always focused on the time-averaged performance optimization.However,the time-history performance is equally important in the design of motion mechanism and flight control system.In this paper,a time-history performance optimization framework based on deep learning and multi-island genetic algorithm is presented,which is designed in order to obtain the optimal two-dimensional flapping wing motion.Firstly,the training dataset for deep learning neural network is constructed based on a validated computational fluid dynamics method.The aerodynamic surrogate model for flapping wing is obtained after the convergence of training.The surrogate model is tested and proved to be able to accurately and quickly predict the time-history curves of lift,thrust and moment.Secondly,the optimization framework is used to optimize the flapping wing motion in two specific cases,in which the optimized propulsive efficiencies have been improved by over 40%compared with the baselines.Thirdly,a dimensionless parameter C_(variation)is proposed to describe the variation of the time-history characteristics,and it is found that C_(variation)of lift varies significantly even under close time-averaged performances.Considering the importance of time-history performance in practical applications,the optimization that integrates the propulsion efficiency as well as C_(variation)is carried out.The final optimal flapping wing motion balances good time-averaged and time-history performance.展开更多
In this paper,we present the development of our latest flapping-wing micro air vehicle(FW-MAV),named Explobird,which features two wings with a wingspan of 195 mm and weighs a mere 25.2 g,enabling it to accomplish vert...In this paper,we present the development of our latest flapping-wing micro air vehicle(FW-MAV),named Explobird,which features two wings with a wingspan of 195 mm and weighs a mere 25.2 g,enabling it to accomplish vertical take-off and hover flight.We devised a novel gear-based mechanism for the flapping system to achieve high lift capability and reliability and conducted extensive testing and analysis on the wings to optimise power matching and lift performance.The Explobird can deliver a peak lift-to-weight ratio of 1.472 and an endurance time of 259 s during hover flight powered by a single-cell LiPo battery.Considering the inherent instability of the prototype,we discuss the derivatives of its longitudinal system,underscoring the importance of feedback control,position of the centre of gravity,and increased damping.To demonstrate the effect of damping enhancement on stability,we also designed a passive stable FW-MAV.Currently,the vehicle is actively stabilised in roll by adjusting the wing root bars and in pitch through high-authority tail control,whereas yaw is passively stabilised.Through a series of flight tests,we successfully demonstrate that our prototype can perform vertical take-off and hover flight under wireless conditions.These promising results position the Explobird as a robust vehicle with high lift capability,paving the way towards the use of FW-MAVs for carrying load equipment in multiple tasks.展开更多
Certain insect species have been observed to exploit the resonance mechanism of their wings.In order to achieve resonance and optimize aerodynamic performance,the conventional approach is to set the flapping frequency...Certain insect species have been observed to exploit the resonance mechanism of their wings.In order to achieve resonance and optimize aerodynamic performance,the conventional approach is to set the flapping frequency of flexible wings based on the Traditional Structural Modal(TSM)analysis.However,there exists controversy among researchers regarding the relationship between frequency and aerodynamic performance.Recognizing that the structural response of wings can be influenced by the surrounding air vibrations,an analysis known as Acoustic Structure Interaction Modal(ASIM)is introduced to calculate the resonant frequency.In this study,Fluid Structure Interaction(FSI)simulations are employed to investigate the aerodynamic performance of flapping wings at modal frequencies derived from both TSM and ASIM analyses.The performance is evaluated for various mass ratios and frequency ratios,and the findings indicate that the deformation and changes in vortex structure exhibit similarities at mass ratios that yield the highest aerodynamic performance.Notably,the flapping frequency associated with the maximum time-averaged vertical force coefficient at each mass ratio closely aligns with the ASIM frequency,as does the frequency corresponding to maximum efficiency.Thus,the ASIM analysis can provide an effective means for predicting the optimal flapping frequency for flexible wings.Furthermore,it enables the prediction that flexible wings with varying mass ratios will exhibit similar deformation and vortex structure changes.This paper offers a fresh perspective on the ongoing debate concerning the resonance mechanism of Flexible Flapping Wings(FFWs)and proposes an effective methodology for predicting their aerodynamic performance.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
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
Although the aerodynamic loading of wind turbine blades under various conditions has been widely studied,the radial distribution of load along the blade under various yaw conditions and with blade flapping phenomena i...Although the aerodynamic loading of wind turbine blades under various conditions has been widely studied,the radial distribution of load along the blade under various yaw conditions and with blade flapping phenomena is poorly understood.This study aims to investigate the effects of second-order flapwise vibration on the mean and fluctuation characteristics of the torque and axial thrust of wind turbines under yaw conditions using computational fluid dynamics(CFD).In the CFD model,the blades are segmented radially to comprehensively analyze the distribution patterns of torque,axial load,and tangential load.The following results are obtained.(i)After applying flapwise vibration,the torque and axial thrust of wind turbines decrease in relation to those of the rigid model,with significantly increased fluctuations.(ii)Flapwise vibration causes the blades to reciprocate along the axial direction,altering the local angle of attack and velocity of the blades relative to the incoming wind flow.This results in the contraction of the torque region from a circular shape to a complex“gear”shape,which is accompanied by evident oscillations.(iii)Compared to the tangential load,the axial load on the blades is more sensitive to flapwise vibration although both exhibit significantly enhanced fluctuations.This study not only reveals the impact of flapwise vibration on wind turbine blade performance,including the reduction of torque and axial thrust and increased operational fluctuations,but also clarifies the radial distribution patterns of blade aerodynamic characteristics,which is of great significance for optimizing wind turbine blade design and reducing fatigue risks.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
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
The current work aims at employing a gradient descent algorithm for optimizing the thrust of a flapping wing. An in-house solver has been employed, along with mesh movement methodologies to capture the dynamics of flo...The current work aims at employing a gradient descent algorithm for optimizing the thrust of a flapping wing. An in-house solver has been employed, along with mesh movement methodologies to capture the dynamics of flow around the airfoil. An efficient framework for implementing the coupled solver and optimization in a multicore environment has been implemented for the generation of optimized solutionsmaximizing thrust performance & computational speed.展开更多
Cicatricial ectropion of the eyelid is an eversion of its edge, which has moved away from the globe. It is frequently the result of cicatricial retraction after trauma. The main risk is the occurrence of a corneal ulc...Cicatricial ectropion of the eyelid is an eversion of its edge, which has moved away from the globe. It is frequently the result of cicatricial retraction after trauma. The main risk is the occurrence of a corneal ulcer or chronic conjunctivitis. Their treatment is often difficult, especially when the ectropion is old and significant. There are several classic techniques for correcting cicatricial ectropions, but the technique of the myocutaneous flap combined with external tarsorrhaphy without damage to the canthal ligament is minimally invasive, not very widespread, yet responds very well to the rules of plastic surgery. We report two cases of post-traumatic cicatricial ectropions of the left lower eyelid, respectively in a 33-year-old and an 87-year-old, treated using this technique. The surgical procedure was performed in two stages, after evaluation of the skin of the flap to be harvested: harvesting of the flap and closure plasty including external tarsorrhaphy. Patient follow-up did not note any complications. This combined technique offers a minimally invasive alternative for the often-delicate treatment of ectropions.展开更多
A robust Reynolds-Averaged Navier-Stokes(RANS)based solver is established to predict the complex unsteady aerodynamic characteristics of the Active Flap Control(AFC)rotor.The complex motion with multiple degrees of fr...A robust Reynolds-Averaged Navier-Stokes(RANS)based solver is established to predict the complex unsteady aerodynamic characteristics of the Active Flap Control(AFC)rotor.The complex motion with multiple degrees of freedom of the Trailing Edge Flap(TEF)is analyzed by employing an inverse nested overset grid method.Simulation of non-rotational and rotational modes of blade motion are carried out to investigate the formation and development of TEF shedding vortex with high-frequency deflection of TEF.Moreover,the mechanism of TEF deflection interference with blade tip vortex and overall rotor aerodynamics is also explored.In nonrotational mode,two bundles of vortices form at the gap ends of TEF and the main blade and merge into a single TEF vortex.Dynamic deflection of the TEF significantly interferes with the blade tip vortex.The position of the blade tip vortex consistently changes,and its frequency is directly related to the frequency of TEF deflection.In rotational mode,the tip vortex forms a helical structure.The end vortices at the gap sides co-swirl and subsequently merge into the concentrated beam of tip vortices,causing fluctuations in the vorticity and axial position of the tip vortex under the rotor.This research concludes with the investigation on suppression of Blade Vortex Interaction(BVI),showing an increase in miss distance and reduction in the vorticity of tip vortex through TEF phase control at a particular control frequency.Through this mechanism,a designed TEF deflection law increases the miss distance by 34.7%and reduces vorticity by 11.9%at the target position,demonstrating the effectiveness of AFC in mitigating BVI.展开更多
Osteoradionecrosis of the temporal bone(ORN-TB)is usually controlled with conservative measures.However,a temporal bone resection may be required in unresponsive cases.The reconstruction of the resulting defects may b...Osteoradionecrosis of the temporal bone(ORN-TB)is usually controlled with conservative measures.However,a temporal bone resection may be required in unresponsive cases.The reconstruction of the resulting defects may be challenging because of the radiation damage to regional tissues.As a result,distant free flaps may be an optimal choice.For instance,the gracilis muscular free flap(GMFF)has consistent vascular anatomy and can be used to reconstruct small defects.We report three cases of uncontrolled ORN-TB requiring an extensive temporal bone resection followed by vascularized obliteration with a GMFF.The patients reported complete control of the main otologic symptoms(otorrhea,otalgia,and aural fullness)and optimal functional and aesthetic outcomes.Finally,the patients reported significant improvement in quality of life despite early postoperative complications.To our knowledge,the GMFF had not been used to obliterate temporal bone defects in patients with ORN-TB.展开更多
The online version of the original article can be found at:https://www.sciopen.com/article/10.26599/JOTO.2025.9540018 Erratum to Journal of Otology,2025,20(2):123-126.https://doi.org/10.26599/JOTO.2025.9540018 The sur...The online version of the original article can be found at:https://www.sciopen.com/article/10.26599/JOTO.2025.9540018 Erratum to Journal of Otology,2025,20(2):123-126.https://doi.org/10.26599/JOTO.2025.9540018 The surnames and given names of these authors are reversed:Saro-Buendía Miguel,Andresen-Lorca Belén,Pérez-García Alberto,Llópez Carratala Nacho,Carreres Polo Joan,Armengot Carceller Miguel,Perolada Valmaña Jose María.It should be Miguel Saro-Buendía,Belén Andresen-Lorca,Alberto Pérez-García,Nacho Llópez Carratala,Joan Carreres Polo,Miguel Armengot Carceller,Jose María Perolada Valmaña.展开更多
Current breast reconstruction evaluations mostly focus on static cosmetic analysis as a measure of the clinical outcomes.Moreover,it is essential to consider the dynamic changes in the reconstructed breast alongside a...Current breast reconstruction evaluations mostly focus on static cosmetic analysis as a measure of the clinical outcomes.Moreover,it is essential to consider the dynamic changes in the reconstructed breast alongside assessments of aesthetic symmetry,functional restoration,complication rates,and long-term stability of the reconstruction.This study aimed to assess the mobility of the reconstructed breast following various breast reconstruction techniques,specifically by comparing deep inferior epigastric perforator(DIEP) flaps and pedicled transverse rectus abdominis musculocutaneous(TRAM) flaps.We conducted a longitudinal case study to investigate the changes in breast movement resulting from different surgical interventions.The comparison showed that DIEP flap reconstruction was more likely to achieve superior breast mobility outcomes than TRAM flap reconstruction.For a better breast aesthetic outcome,it is fundamental to improve the awareness of the dynamic evaluation of the reconstructed breast at the surgical strategy level.展开更多
Objectives:To assess outcomes of rectourethral fistula repair utilizing a gracilis flap in a largely radiated cohort.Patients and Methods:We performed a retrospective review of all gracilis interposition flap reconstr...Objectives:To assess outcomes of rectourethral fistula repair utilizing a gracilis flap in a largely radiated cohort.Patients and Methods:We performed a retrospective review of all gracilis interposition flap reconstruction surgeries performed for RUF at a university hospital in South Carolina between January 2010 and June 2023.All repairs utilized a multidisciplinary approach with urology,colorectal,and plastic surgery teams.Postoperatively,patients were maximally drained with foley catheter and suprapubic tube(SPT).Initial voiding cystourethrogram(VCUG)was performed at 4 weeks post-repair.If there was a persistent leak,catheter drainage was maintained for 4 additional weeks and VCUG was repeated.Success was defined as absence of leak on VCUG within 3 months after surgery.Results:22 patients met inclusion criteria.68%of patients had history of external beam radiation therapy(EBRT),13.6%had brachytherapy,and 40.9%had cryotherapy.Initial post-operative VCUG was negative in 10 patients(45.5%).Of the 12 patients with a persistent fistula,5(42%)had no evidence of fistula on subsequent VCUG after 4 weeks.Overall,68%of patients were successfully treated with gracilis interposition flap.There was a significant difference of repair success based on EBRT status(p<0.05).Conclusions:We report a success rate of 68%for gracilis flap repair of RUF.Our cohort had a higher rate of prior radiation therapy compared to other studies.A clinically significant portion of patients with an initial positive VCUG will seal their fistula with prolonged catheter drainage.Gracilis interposition flap is a reasonable surgical treatment for RUF.展开更多
Background: The lumbar artery perforator(LAP) flap is an important autologous option in breast reconstruction.As the lumbar perforator flap is relatively new in this field,several questions remain regarding preoperati...Background: The lumbar artery perforator(LAP) flap is an important autologous option in breast reconstruction.As the lumbar perforator flap is relatively new in this field,several questions remain regarding preoperative preparation,especially concerning computed tomography(CT) and magnetic resonance imaging of the donor site.The objective of this study was to aid the surgical approach to the LAP flap in female patients by precisely determining the characteristics of the lumbar perforators.Methods: We retrospectively reviewed the computed tomographic angiography images of 20 patients who underwent evaluation of the perforator positions from the four lumbar arteries.Four characteristics were studied:length,diameter,path of the lumbar pedicle,and thickness of the tissues available for transfer.Results: We analyzed 20 CT images,identifying 149 perforating vessels of the lumbar artery.The most suitable perforator for flap harvesting was the L4 perforator,which exhibited a larger diameter,a greater number of perforasomes,and a higher percentage of the cutaneous-septal tract.Conclusion: The LAP flap is a viable option for breast reconstruction and as a free flap in women.The L4 perforator artery is the most suitable for harvesting,owing to its superior perfusion capacity,diameter,and course;however,an interposition graft may be required to lengthen the vascular pedicle.展开更多
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 National Natural Science Foundation of China under Grants No.52175277 and 12272318,and ND Basic Research Funds under Grants G2022WDwas supported in part by the Basic Research Program of Shenzhen under GrantJCYJ20190806142816524.
文摘This paper is based on a previously developed bio-inspired Flapping Wing Aerial Vehicle(FWAV),RoboFalcon,which can fly with a morphing-coupled flapping pattern.In this paper,a simple flapping stroke control system based on Hall effect sensors is designed and applied,which is capable of assigning different up-and down-stroke speeds for the RoboFalcon platform to achieve an adjustable downstroke ratio.The aerodynamic and power characteristics of the morphing-coupled flapping pattern and the conventional flapping pattern with varying downstroke ratios are measured through a wind tunnel experiment,and the corresponding aerodynamic models are developed and analyzed by the nonlinear least squares method.The relatively low power consumption of the slow-downstroke mode of this vehicle is verified through outdoor flight tests.The results of wind tunnel experiments and flight tests indicate that increased downstroke duration can improve aerodynamic and power performance for the RoboFalcon platform.
基金mainly supported by the National Natural Science Foundation of China (No. 52175277, 52275293)Resources provided by the Basic Research Program of Shenzhen, China (No. JCYJ 20190806142816524)the Guangdong Basic and Applied Basic Research Foundation, China (No. 2023A1515010774)。
文摘Birds and bats retract and stretch their wings dynamically during each flap in level flights, implying intriguing mechanisms for the aerodynamic performance improvement of flapping wings. A numerical investigation into the aerodynamic effects of such bio-inspired concept in forward flights has been performed based on a three-dimensional wing in plunging motion and a twosection wing in flapping motion. The currently considered Reynolds number and Strouhal number are Re=1.5×10^(5) and St=0.3, respectively. During the research, the mean angle of attack is varied in relatively wide ranges to achieve lift-thrust interconversion for the wings. The conclusive results show that dynamical spanwise retraction and stretch has induced three absolutely desirable scenarios for the oscillating wings in forward flights, namely producing more lift and consuming less power for a given thrust generation, producing more thrust and consuming less power for a given lift generation, and producing more lift and more thrust while consuming less power. Furthermore,the morphing wings have alleviated periodical aerodynamic load fluctuations compared with the non-morphing baseline. The mechanism of the aerodynamic effects of the bionic morphing mode is analyzed with the aid of field visualization. The current article is the first to reveal the absolute advantages of the bionic spanwise morphing. Hopefully, it may help comprehend the behaviors of natural fliers and provide inspirations for performance enhancement of micro artificial flappingwing vehicles.
基金supported by the National Nature Science Foundation of China(Nos.12102259,12202273)the China Postdoctoral Science Foundation(No.2018M642007)。
文摘Insects usually fly by passively rotating wings,which has been applied to the design of flapping-wing Micro-Air Vehicles(MAVs)to reduce mechanical complexity.In this paper,a robotic passive rotating-wing model is designed to investigate wing kinematics and lift generation,which are measured by a high-speed camera and a force transducer,respectively.In addition,flow fields are measured using the Particle Image Velocimetry(PIV).Experimental results demonstrate that passive rotating motion has a coordinative relationship with actively stroking motion.As the stroke amplitude or frequency increases,the rotating amplitude is enlarged.To characterize the active stroking motion,a driving Reynolds number Redrivingis defined,which varies from 68 to 366 in this study.Moving the gravity center of the wing towards trailing ed ge induces the increase of additional torque M,which decreases the wing rotating amplitude and promotes the advance of wing rotation.We find that the timing of wing rotation is gradually delayed and the mean lift coefficient C^(-)_(L)monotonously decreases as Redrivingincreases.By increasing the additional torque M,C^(-)_(L)is slightly improved and approaches to the lift coefficient of a real fruit fly at driving Re approximately equal to 230.The instantaneous lifts combined with the vortical structures further demonstrate that the lift generation associated with wing rotation is mainly attributed to the growth of the LeadingEdge Vortex(LEV)and the passive wake capture mechanism.Passive wake capture is influenced by LEV,reversal stroke motion and wing additional torque together,which can only maintain the lift at a high level for a considerable period.The high-lift generation mechanisms of flapping and passive rotating flight could shed light on the simplified design of MAVs and the improvement of their aerodynamic performance.
基金This work was supported by the specialized research projects of Huanjiang Laboratory,and the Defence Industrial Technology Development Programme,China(Nos.JCKY2019205A006,JCKY2021205B003).
文摘Flapping Wing Micro Aerial Vehicles(FWMAVs)have caused great concern in various fields because of their high efficiency and maneuverability.Flapping wing motion is a very important factor that affects the performance of the aircraft,and previous works have always focused on the time-averaged performance optimization.However,the time-history performance is equally important in the design of motion mechanism and flight control system.In this paper,a time-history performance optimization framework based on deep learning and multi-island genetic algorithm is presented,which is designed in order to obtain the optimal two-dimensional flapping wing motion.Firstly,the training dataset for deep learning neural network is constructed based on a validated computational fluid dynamics method.The aerodynamic surrogate model for flapping wing is obtained after the convergence of training.The surrogate model is tested and proved to be able to accurately and quickly predict the time-history curves of lift,thrust and moment.Secondly,the optimization framework is used to optimize the flapping wing motion in two specific cases,in which the optimized propulsive efficiencies have been improved by over 40%compared with the baselines.Thirdly,a dimensionless parameter C_(variation)is proposed to describe the variation of the time-history characteristics,and it is found that C_(variation)of lift varies significantly even under close time-averaged performances.Considering the importance of time-history performance in practical applications,the optimization that integrates the propulsion efficiency as well as C_(variation)is carried out.The final optimal flapping wing motion balances good time-averaged and time-history performance.
基金supported by the National Natural Science Foundation of China under Grant No.51975023&52322501supported in part by the National Natural Science Foundation of China under Grant No.U22B2040.
文摘In this paper,we present the development of our latest flapping-wing micro air vehicle(FW-MAV),named Explobird,which features two wings with a wingspan of 195 mm and weighs a mere 25.2 g,enabling it to accomplish vertical take-off and hover flight.We devised a novel gear-based mechanism for the flapping system to achieve high lift capability and reliability and conducted extensive testing and analysis on the wings to optimise power matching and lift performance.The Explobird can deliver a peak lift-to-weight ratio of 1.472 and an endurance time of 259 s during hover flight powered by a single-cell LiPo battery.Considering the inherent instability of the prototype,we discuss the derivatives of its longitudinal system,underscoring the importance of feedback control,position of the centre of gravity,and increased damping.To demonstrate the effect of damping enhancement on stability,we also designed a passive stable FW-MAV.Currently,the vehicle is actively stabilised in roll by adjusting the wing root bars and in pitch through high-authority tail control,whereas yaw is passively stabilised.Through a series of flight tests,we successfully demonstrate that our prototype can perform vertical take-off and hover flight under wireless conditions.These promising results position the Explobird as a robust vehicle with high lift capability,paving the way towards the use of FW-MAVs for carrying load equipment in multiple tasks.
基金This study was co-supported by the National Natural Science Foundation of China(No.52275293)the Guangdong Basic and Applied Basic Research Foundation,China(No.2023A1515010774)+1 种基金the Basic Research Program of Shenzhen,China(No.JCYJ 20190806142816524)the National Key Laboratory of Science and Technology on Aerodynamic Design and Research,China(No.61422010301).
文摘Certain insect species have been observed to exploit the resonance mechanism of their wings.In order to achieve resonance and optimize aerodynamic performance,the conventional approach is to set the flapping frequency of flexible wings based on the Traditional Structural Modal(TSM)analysis.However,there exists controversy among researchers regarding the relationship between frequency and aerodynamic performance.Recognizing that the structural response of wings can be influenced by the surrounding air vibrations,an analysis known as Acoustic Structure Interaction Modal(ASIM)is introduced to calculate the resonant frequency.In this study,Fluid Structure Interaction(FSI)simulations are employed to investigate the aerodynamic performance of flapping wings at modal frequencies derived from both TSM and ASIM analyses.The performance is evaluated for various mass ratios and frequency ratios,and the findings indicate that the deformation and changes in vortex structure exhibit similarities at mass ratios that yield the highest aerodynamic performance.Notably,the flapping frequency associated with the maximum time-averaged vertical force coefficient at each mass ratio closely aligns with the ASIM frequency,as does the frequency corresponding to maximum efficiency.Thus,the ASIM analysis can provide an effective means for predicting the optimal flapping frequency for flexible wings.Furthermore,it enables the prediction that flexible wings with varying mass ratios will exhibit similar deformation and vortex structure changes.This paper offers a fresh perspective on the ongoing debate concerning the resonance mechanism of Flexible Flapping Wings(FFWs)and proposes an effective methodology for predicting their aerodynamic performance.
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 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supported by the National Natural Science Foundation of China(51866012)the Major Project of the Natural Science Foundation of Inner Mongolia Autonomous Region(2018ZD08)the Fundamental Research Funds for the Central Universities of Inner Mongolia Autonomous Region(JY20220037).
文摘Although the aerodynamic loading of wind turbine blades under various conditions has been widely studied,the radial distribution of load along the blade under various yaw conditions and with blade flapping phenomena is poorly understood.This study aims to investigate the effects of second-order flapwise vibration on the mean and fluctuation characteristics of the torque and axial thrust of wind turbines under yaw conditions using computational fluid dynamics(CFD).In the CFD model,the blades are segmented radially to comprehensively analyze the distribution patterns of torque,axial load,and tangential load.The following results are obtained.(i)After applying flapwise vibration,the torque and axial thrust of wind turbines decrease in relation to those of the rigid model,with significantly increased fluctuations.(ii)Flapwise vibration causes the blades to reciprocate along the axial direction,altering the local angle of attack and velocity of the blades relative to the incoming wind flow.This results in the contraction of the torque region from a circular shape to a complex“gear”shape,which is accompanied by evident oscillations.(iii)Compared to the tangential load,the axial load on the blades is more sensitive to flapwise vibration although both exhibit significantly enhanced fluctuations.This study not only reveals the impact of flapwise vibration on wind turbine blade performance,including the reduction of torque and axial thrust and increased operational fluctuations,but also clarifies the radial distribution patterns of blade aerodynamic characteristics,which is of great significance for optimizing wind turbine blade design and reducing fatigue risks.
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.
文摘The current work aims at employing a gradient descent algorithm for optimizing the thrust of a flapping wing. An in-house solver has been employed, along with mesh movement methodologies to capture the dynamics of flow around the airfoil. An efficient framework for implementing the coupled solver and optimization in a multicore environment has been implemented for the generation of optimized solutionsmaximizing thrust performance & computational speed.
文摘Cicatricial ectropion of the eyelid is an eversion of its edge, which has moved away from the globe. It is frequently the result of cicatricial retraction after trauma. The main risk is the occurrence of a corneal ulcer or chronic conjunctivitis. Their treatment is often difficult, especially when the ectropion is old and significant. There are several classic techniques for correcting cicatricial ectropions, but the technique of the myocutaneous flap combined with external tarsorrhaphy without damage to the canthal ligament is minimally invasive, not very widespread, yet responds very well to the rules of plastic surgery. We report two cases of post-traumatic cicatricial ectropions of the left lower eyelid, respectively in a 33-year-old and an 87-year-old, treated using this technique. The surgical procedure was performed in two stages, after evaluation of the skin of the flap to be harvested: harvesting of the flap and closure plasty including external tarsorrhaphy. Patient follow-up did not note any complications. This combined technique offers a minimally invasive alternative for the often-delicate treatment of ectropions.
基金supported by the National Natural Science Foundation of China(No.11972190)。
文摘A robust Reynolds-Averaged Navier-Stokes(RANS)based solver is established to predict the complex unsteady aerodynamic characteristics of the Active Flap Control(AFC)rotor.The complex motion with multiple degrees of freedom of the Trailing Edge Flap(TEF)is analyzed by employing an inverse nested overset grid method.Simulation of non-rotational and rotational modes of blade motion are carried out to investigate the formation and development of TEF shedding vortex with high-frequency deflection of TEF.Moreover,the mechanism of TEF deflection interference with blade tip vortex and overall rotor aerodynamics is also explored.In nonrotational mode,two bundles of vortices form at the gap ends of TEF and the main blade and merge into a single TEF vortex.Dynamic deflection of the TEF significantly interferes with the blade tip vortex.The position of the blade tip vortex consistently changes,and its frequency is directly related to the frequency of TEF deflection.In rotational mode,the tip vortex forms a helical structure.The end vortices at the gap sides co-swirl and subsequently merge into the concentrated beam of tip vortices,causing fluctuations in the vorticity and axial position of the tip vortex under the rotor.This research concludes with the investigation on suppression of Blade Vortex Interaction(BVI),showing an increase in miss distance and reduction in the vorticity of tip vortex through TEF phase control at a particular control frequency.Through this mechanism,a designed TEF deflection law increases the miss distance by 34.7%and reduces vorticity by 11.9%at the target position,demonstrating the effectiveness of AFC in mitigating BVI.
文摘Osteoradionecrosis of the temporal bone(ORN-TB)is usually controlled with conservative measures.However,a temporal bone resection may be required in unresponsive cases.The reconstruction of the resulting defects may be challenging because of the radiation damage to regional tissues.As a result,distant free flaps may be an optimal choice.For instance,the gracilis muscular free flap(GMFF)has consistent vascular anatomy and can be used to reconstruct small defects.We report three cases of uncontrolled ORN-TB requiring an extensive temporal bone resection followed by vascularized obliteration with a GMFF.The patients reported complete control of the main otologic symptoms(otorrhea,otalgia,and aural fullness)and optimal functional and aesthetic outcomes.Finally,the patients reported significant improvement in quality of life despite early postoperative complications.To our knowledge,the GMFF had not been used to obliterate temporal bone defects in patients with ORN-TB.
文摘The online version of the original article can be found at:https://www.sciopen.com/article/10.26599/JOTO.2025.9540018 Erratum to Journal of Otology,2025,20(2):123-126.https://doi.org/10.26599/JOTO.2025.9540018 The surnames and given names of these authors are reversed:Saro-Buendía Miguel,Andresen-Lorca Belén,Pérez-García Alberto,Llópez Carratala Nacho,Carreres Polo Joan,Armengot Carceller Miguel,Perolada Valmaña Jose María.It should be Miguel Saro-Buendía,Belén Andresen-Lorca,Alberto Pérez-García,Nacho Llópez Carratala,Joan Carreres Polo,Miguel Armengot Carceller,Jose María Perolada Valmaña.
文摘Current breast reconstruction evaluations mostly focus on static cosmetic analysis as a measure of the clinical outcomes.Moreover,it is essential to consider the dynamic changes in the reconstructed breast alongside assessments of aesthetic symmetry,functional restoration,complication rates,and long-term stability of the reconstruction.This study aimed to assess the mobility of the reconstructed breast following various breast reconstruction techniques,specifically by comparing deep inferior epigastric perforator(DIEP) flaps and pedicled transverse rectus abdominis musculocutaneous(TRAM) flaps.We conducted a longitudinal case study to investigate the changes in breast movement resulting from different surgical interventions.The comparison showed that DIEP flap reconstruction was more likely to achieve superior breast mobility outcomes than TRAM flap reconstruction.For a better breast aesthetic outcome,it is fundamental to improve the awareness of the dynamic evaluation of the reconstructed breast at the surgical strategy level.
文摘Objectives:To assess outcomes of rectourethral fistula repair utilizing a gracilis flap in a largely radiated cohort.Patients and Methods:We performed a retrospective review of all gracilis interposition flap reconstruction surgeries performed for RUF at a university hospital in South Carolina between January 2010 and June 2023.All repairs utilized a multidisciplinary approach with urology,colorectal,and plastic surgery teams.Postoperatively,patients were maximally drained with foley catheter and suprapubic tube(SPT).Initial voiding cystourethrogram(VCUG)was performed at 4 weeks post-repair.If there was a persistent leak,catheter drainage was maintained for 4 additional weeks and VCUG was repeated.Success was defined as absence of leak on VCUG within 3 months after surgery.Results:22 patients met inclusion criteria.68%of patients had history of external beam radiation therapy(EBRT),13.6%had brachytherapy,and 40.9%had cryotherapy.Initial post-operative VCUG was negative in 10 patients(45.5%).Of the 12 patients with a persistent fistula,5(42%)had no evidence of fistula on subsequent VCUG after 4 weeks.Overall,68%of patients were successfully treated with gracilis interposition flap.There was a significant difference of repair success based on EBRT status(p<0.05).Conclusions:We report a success rate of 68%for gracilis flap repair of RUF.Our cohort had a higher rate of prior radiation therapy compared to other studies.A clinically significant portion of patients with an initial positive VCUG will seal their fistula with prolonged catheter drainage.Gracilis interposition flap is a reasonable surgical treatment for RUF.
文摘Background: The lumbar artery perforator(LAP) flap is an important autologous option in breast reconstruction.As the lumbar perforator flap is relatively new in this field,several questions remain regarding preoperative preparation,especially concerning computed tomography(CT) and magnetic resonance imaging of the donor site.The objective of this study was to aid the surgical approach to the LAP flap in female patients by precisely determining the characteristics of the lumbar perforators.Methods: We retrospectively reviewed the computed tomographic angiography images of 20 patients who underwent evaluation of the perforator positions from the four lumbar arteries.Four characteristics were studied:length,diameter,path of the lumbar pedicle,and thickness of the tissues available for transfer.Results: We analyzed 20 CT images,identifying 149 perforating vessels of the lumbar artery.The most suitable perforator for flap harvesting was the L4 perforator,which exhibited a larger diameter,a greater number of perforasomes,and a higher percentage of the cutaneous-septal tract.Conclusion: The LAP flap is a viable option for breast reconstruction and as a free flap in women.The L4 perforator artery is the most suitable for harvesting,owing to its superior perfusion capacity,diameter,and course;however,an interposition graft may be required to lengthen the vascular pedicle.
