In this work, we develop an artificial foldable wing that mimics the hind wing of a beetle （Allomyrina dichotoma）. In real flight, the beetle unfolds forewings and hind wings, and maintains the unfolded configuratio...In this work, we develop an artificial foldable wing that mimics the hind wing of a beetle （Allomyrina dichotoma）. In real flight, the beetle unfolds forewings and hind wings, and maintains the unfolded configuration unless it is exhausted. The artificial wing has to be able to maintain a fully unfolded configuration while flapping at a desirable flapping frequency. The artificial foldable hind wing developed in this work is based on two four-bar linkages which adapt the behaviors of the beetle＇s hind wing. The four-bar-linkages are designed to mimic rotational motion of the wing base and the vein folding/unfolding motion of the beetle＇s hind wing. The behavior of the artificial wings, which are installed in a flapping-wing system, is observed using a high-speed camera. The observation shows that the wing could maintain a fully unfolded configuration during flapping motion. A series of thrust measurements are also conducted to estimate the force generated by the flapping-wing system with foldable artificial wings. Although the artificial foldable wings give added burden to the flapping-wing system because of its weight, the thrust measurement results show that the flapping-wing system could still generate reasonable thrust.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
Bird-like flapping-wing vehicles with a high aspect ratio have the potential to fulfill missions given to micro air vehicles,such as high-altitude reconnaissance,surveillance,rescue,and bird group guidance,due to thei...Bird-like flapping-wing vehicles with a high aspect ratio have the potential to fulfill missions given to micro air vehicles,such as high-altitude reconnaissance,surveillance,rescue,and bird group guidance,due to their good loading and long endurance capacities.Biologists and aeronautical researchers have explored the mystery of avian flight and made efforts to reproduce flapping flight in bioinspired aircraft for decades.However,the cognitive depth from theory to practice is still very limited.The mechanism of generating sufficient lift and thrust during avian flight is still not fully understood.Moving wings with unique biological structures such as feathers make modeling,simulation,experimentation,and analysis much more difficult.This paper reviews the research progress on bird-like flapping wings from flight mechanisms to modeling.Commonly used numerical computing methods are briefly compared.The aeroelastic problems are also highlighted.The results of the investigation show that a leading-edge vortex can be found during avian flight.Its induction and maintenance may have a close relationship with wing configuration,kinematics and deformation.The present models of flapping wings are mainly two-dimensional airfoils or three-dimensional single root-jointed geometric plates,which still exhibit large differences from real bird wings.Aeroelasticity is encouraged to consider the nonignorable effect on aerodynamic performance due to large-scale nonlinear deformation.Introducing appropriate flexibility can improve the peak values and efficiencies of lift and thrust,but the detailed conclusions always have strong background dependence.展开更多
文摘In this work, we develop an artificial foldable wing that mimics the hind wing of a beetle （Allomyrina dichotoma）. In real flight, the beetle unfolds forewings and hind wings, and maintains the unfolded configuration unless it is exhausted. The artificial wing has to be able to maintain a fully unfolded configuration while flapping at a desirable flapping frequency. The artificial foldable hind wing developed in this work is based on two four-bar linkages which adapt the behaviors of the beetle＇s hind wing. The four-bar-linkages are designed to mimic rotational motion of the wing base and the vein folding/unfolding motion of the beetle＇s hind wing. The behavior of the artificial wings, which are installed in a flapping-wing system, is observed using a high-speed camera. The observation shows that the wing could maintain a fully unfolded configuration during flapping motion. A series of thrust measurements are also conducted to estimate the force generated by the flapping-wing system with foldable artificial wings. Although the artificial foldable wings give added burden to the flapping-wing system because of its weight, the thrust measurement results show that the flapping-wing system could still generate reasonable thrust.
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.
文摘Bird-like flapping-wing vehicles with a high aspect ratio have the potential to fulfill missions given to micro air vehicles,such as high-altitude reconnaissance,surveillance,rescue,and bird group guidance,due to their good loading and long endurance capacities.Biologists and aeronautical researchers have explored the mystery of avian flight and made efforts to reproduce flapping flight in bioinspired aircraft for decades.However,the cognitive depth from theory to practice is still very limited.The mechanism of generating sufficient lift and thrust during avian flight is still not fully understood.Moving wings with unique biological structures such as feathers make modeling,simulation,experimentation,and analysis much more difficult.This paper reviews the research progress on bird-like flapping wings from flight mechanisms to modeling.Commonly used numerical computing methods are briefly compared.The aeroelastic problems are also highlighted.The results of the investigation show that a leading-edge vortex can be found during avian flight.Its induction and maintenance may have a close relationship with wing configuration,kinematics and deformation.The present models of flapping wings are mainly two-dimensional airfoils or three-dimensional single root-jointed geometric plates,which still exhibit large differences from real bird wings.Aeroelasticity is encouraged to consider the nonignorable effect on aerodynamic performance due to large-scale nonlinear deformation.Introducing appropriate flexibility can improve the peak values and efficiencies of lift and thrust,but the detailed conclusions always have strong background dependence.
