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A Flight Mechanics-Centric Review of Bird-Scale Flapping Flight

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This paper reviews the flight mechanics and control of birds and bird-size aircraft. It is intended to fill a niche in the current survey literature which focuses primarily on the aerodynamics, flight dynamics and control of insect scale flight. We review the flight mechanics from first principles and summarize some recent results on the stability and control of birds and bird-scale aircraft. Birds spend a considerable portion of their flight in the gliding (i.e., non-flapping) phase. Therefore, we also review the stability and control of gliding flight, and particularly those aspects which are derived from the unique control features of birds.
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... In [18], the averaged dynamic model of a flapping wing robot was established with the force-moment method for describing the robot motion. In [19], the dynamic model of a bird-like robot was established with the strip theory to calculate the aerodynamic force in the flight. Based on the Euler method, Chirarattananon et al., established the dynamic model of a robot to obtain the attitude dynamics, and calculated the total torques imposed on the robot joints [20]. ...
... In this study, the movement of the rigid wings is simplified into only up-down flapping. e kinematic model of the robot is given as follows [19,25]: ...
... Referring to references [19,[37][38][39], the physical model, the kinematic model and the dynamic model were separately established in this study. e 3D physical model with the same parameters as the robot prototype was built in this study, which is much nearer to real robots compared with 1D or 2D model in references [14,39,43,44] e same as references [17,19,40,41], the kinematic model of the robot was established in this study. ...
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The flight mechanism of a bird-like flapping wing robot at a low Reynolds number was studied in this study for improving the robot performances. Both the physical model and the kinematic model were first established. The dynamic model of the robot at a low Reynolds number was built with the RANS (Reynolds-averaged Navier-Stokes) equations and the Spalart-Allmaras turbulence model. The flight experiments were carried out and the results were discussed. Lift and drag coefficient curves show that it generates upward lift and forward thrust in the phase that the wing flaps downwards, the rate of the coefficient curves is the biggest when the flapping direction changes. Pressure contours indicate that small vortexes with high pressure values appear at the wing edges. There are four velocity vortex groups in total at the front and back of the wing in the velocity contours. Some methods for improving the robot flight efficiency and the robot strength as well as the stitching position of the robot skin have been obtained from the above results. The methods provide the important guidance for the stable flights of the flapping wing robot with the high efficiency.
... According to the experimental formula of the flapping frequencies of birds, except hummingbirds [140] , there is (8) 0. 27 3.98 f m   in which f represents the flapping frequency, m denotes the mass of the bird. Therefore, the flapping frequencies of large birds with high aspect ratio may be close to their wings structural natural frequencies [184] , which increase the complexity of the aeroelastic problem. As a result, aeroelastic characteristics of insects, or even small birds, may differ from those of large birds. ...
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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.
... Thus, the angles induced due to the motions of flapping wings are equal in magnitude for the right and left wings. Since the sweeping motion is negligible for avian-scale forward flight (Paranjape et al. 26 ), it has not been incorporated in the current analysis. The kinematics for plunging and twisting are given by ...
Article
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... Some works use numerical methods for model-based trajectory planning [30,16]. For instance, numerical solutions of the Navier-Stokes equations have been used [28], but they are too expensive computationally for real-time implementation. Other approaches use probabilistic motion planners [35,17] integrating kinodynamic constraints or evolutionary algorithms [23], but again, tractable models are necessary not to exceed computational requirements. ...
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Chapter
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