Wing Kinematics in a Hovering Dronefly Minimize Power Expenditure

SUMMARYThe lift and power requirements for hovering flight in Drosophila virilis were studied using the method of computational fluid dynamics. The Navier-Stokes equations were solved numerically. The solution provided the flow velocity and pressure fields, from which the unsteady aerodynamic forces and moments were obtained. The inertial torques due to the acceleration of the wing mass were computed analytically. On the basis of the aerodynamic forces and moments and the inertial torques, the lift and power requirements for hovering flight were obtained.For the fruit fly Drosophila virilis in hovering flight (with symmetrical rotation), a midstroke angle of attack of approximately 37°was needed for the mean lift to balance the insect weight, which agreed with observations. The mean drag on the wings over an up- or downstroke was approximately 1.27 times the mean lift or insect weight (i.e. the wings of this tiny insect must overcome a drag that is approximately 27 % larger than its weight to produce a lift equal to its weight). The body-mass-specific power was 28.7 W kg-1, the muscle-mass-specific power was 95.7 W kg-1 and the muscle efficiency was 17 %.With advanced rotation, larger lift was produced than with symmetrical rotation, but it was more energy-demanding, i.e. the power required per unit lift was much larger. With delayed rotation, much less lift was produced than with symmetrical rotation at almost the same power expenditure; again, the power required per unit lift was much larger. On the basis of the calculated results for power expenditure, symmetrical rotation should be used for balanced, long-duration flight and advanced rotation and delayed rotation should be used for flight control and manoeuvring. This agrees with observations.

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Optimizing the structure and movement of a robotic bat with biological kinematic synergies

The International Journal of Robotics Research ◽

10.1177/0278364918804654 ◽

2018 ◽

Vol 37 (10) ◽

pp. 1233-1252 ◽

Cited By ~ 2

Author(s):

Jonathan Hoff ◽

Alireza Ramezani ◽

Soon-Jo Chung ◽

Seth Hutchinson

Keyword(s):

Principal Component Analysis ◽

Topological Structure ◽

Degrees Of Freedom ◽

Dimensional Space ◽

Principal Component ◽

Biologically Inspired ◽

Wing Kinematics ◽

Wing Motion ◽

Kinematic Synergies ◽

Low Dimensional

In this article, we present methods to optimize the design and flight characteristics of a biologically inspired bat-like robot. In previous, work we have designed the topological structure for the wing kinematics of this robot; here we present methods to optimize the geometry of this structure, and to compute actuator trajectories such that its wingbeat pattern closely matches biological counterparts. Our approach is motivated by recent studies on biological bat flight that have shown that the salient aspects of wing motion can be accurately represented in a low-dimensional space. Although bats have over 40 degrees of freedom (DoFs), our robot possesses several biologically meaningful morphing specializations. We use principal component analysis (PCA) to characterize the two most dominant modes of biological bat flight kinematics, and we optimize our robot’s parametric kinematics to mimic these. The method yields a robot that is reduced from five degrees of actuation (DoAs) to just three, and that actively folds its wings within a wingbeat period. As a result of mimicking synergies, the robot produces an average net lift improvesment of 89% over the same robot when its wings cannot fold.

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Influence of wing kinematics on aerodynamic performance in hovering insect flight

Journal of Fluid Mechanics ◽

10.1017/s0022112007009172 ◽

2007 ◽

Vol 594 ◽

pp. 341-368 ◽

Cited By ~ 95

Author(s):

FRANK M. BOS ◽

D. LENTINK ◽

B. W. VAN OUDHEUSDEN ◽

H. BIJL

Keyword(s):

Insect Flight ◽

Fruit Fly ◽

Aerodynamic Performance ◽

Navier Stokes ◽

Insect Wing ◽

Wing Kinematics ◽

Drag Forces ◽

Kinematic Models ◽

Characteristic Features ◽

Lift And Drag

The influence of different wing kinematic models on the aerodynamic performance of a hovering insect is investigated by means of two-dimensional time-dependent Navier–Stokes simulations. For this, simplified models are compared with averaged representations of the hovering fruit fly wing kinematics. With increasing complexity, a harmonic model, a Robofly model and two more-realistic fruit fly models are considered, all dynamically scaled at Re = 110. To facilitate the comparison, the parameters of the models were selected such that their mean quasi-steady lift coefficients were matched. Details of the vortex dynamics, as well as the resulting lift and drag forces, were studied.The simulation results reveal that the fruit fly wing kinematics result in forces that differ significantly from those resulting from the simplified wing kinematic models. In addition, light is shed on the effect of different characteristic features of the insect wing motion. The angle of attack variation used by fruit flies increases aerodynamic performance, whereas the deviation is probably used for levelling the forces over the cycle.

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Operation of the alula as an indicator of gear change in hoverflies

Journal of The Royal Society Interface ◽

10.1098/rsif.2011.0617 ◽

2011 ◽

Vol 9 (71) ◽

pp. 1194-1207 ◽

Cited By ~ 26

Author(s):

Simon M. Walker ◽

Adrian L. R. Thomas ◽

Graham K. Taylor

Keyword(s):

High Speed ◽

Aerodynamic Force ◽

Angular Acceleration ◽

The State ◽

The Body ◽

Kinematic Parameters ◽

Wing Kinematics ◽

Change Mechanism ◽

The Third ◽

Gear Change

The alula is a hinged flap found at the base of the wings of most brachyceran Diptera. The alula accounts for up to 10 per cent of the total wing area in hoverflies (Syrphidae), and its hinged arrangement allows the wings to be swept back over the thorax and abdomen at rest. The alula is actuated via the third axillary sclerite, which is a component of the wing hinge that is involved in wing retraction and control. The third axillary sclerite has also been implicated in the gear change mechanism of flies. This mechanism allows rapid switching between different modes of wing kinematics, by imposing or removing contact with a mechanical stop limiting movement of the wing during the lower half of the downstroke. The alula operates in two distinct states during flight—flipped or flat—and we hypothesize that its state indicates switching between different flight modes. We used high-speed digital video of free-flying hoverflies ( Eristalis tenax and Eristalis pertinax ) to investigate whether flipping of the alula was associated with changes in wing and body kinematics. We found that alula state was associated with different distributions of multiple wing kinematic parameters, including stroke amplitude, stroke deviation angle, downstroke angle of incidence and timing of supination. Changes in all of these parameters have previously been linked to gear change in flies. Symmetric flipping of the alulae was associated with changes in the symmetric linear acceleration of the body, while asymmetric flipping of the alulae was associated with asymmetric angular acceleration of the body. We conclude that the wings produce less aerodynamic force when the alula is flipped, largely as a result of the accompanying changes in wing kinematics. The alula changes state at mid-downstroke, which is the point at which the gear change mechanism is known to come into effect. This transition is accompanied by changes in the other wing kinematic parameters. We therefore find that the state of the alula is linked to the same parameters as are affected by the gear change mechanism. We conclude that the state of the alula does indeed indicate the operation of different flight modes in Eristalis , and infer that a likely mechanism for these changes in flight mode is the gear change mechanism.

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