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Active and passive stabilization of body pitch in insect flight.

Ristroph L, Ristroph G, Morozova S, Bergou AJ, Chang S, Guckenheimer J, Wang ZJ, Cohen I - J R Soc Interface (2013)

Bottom Line: Flying insects have evolved sophisticated sensory-motor systems, and here we argue that such systems are used to keep upright against intrinsic flight instabilities.By glueing magnets to fruit flies and perturbing their flight using magnetic impulses, we show that these insects employ active control that is indeed fast relative to the instability.Finally, we extend this framework to unify the control strategies used by hovering animals and also furnish criteria for achieving pitch stability in flapping-wing robots.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, Cornell University, Ithaca, NY 14853, USA. ristroph@cims.nyu.edu

ABSTRACT
Flying insects have evolved sophisticated sensory-motor systems, and here we argue that such systems are used to keep upright against intrinsic flight instabilities. We describe a theory that predicts the instability growth rate in body pitch from flapping-wing aerodynamics and reveals two ways of achieving balanced flight: active control with sufficiently rapid reactions and passive stabilization with high body drag. By glueing magnets to fruit flies and perturbing their flight using magnetic impulses, we show that these insects employ active control that is indeed fast relative to the instability. Moreover, we find that fruit flies with their control sensors disabled can keep upright if high-drag fibres are also attached to their bodies, an observation consistent with our prediction for the passive stability condition. Finally, we extend this framework to unify the control strategies used by hovering animals and also furnish criteria for achieving pitch stability in flapping-wing robots.

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A force diagram shows how an instability in body pitch develops. During hovering, the wings flap back and forth to produce lift that balances body weight. A perturbation to the pitch orientation causes the insect to move forwards. Drag on the wings then becomes unbalanced, inducing a torque that tends to tip the insect backwards. This simplified picture highlights some of the important effects to be incorporated in a model of the pitch dynamics. (Online version in colour.)
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RSIF20130237F3: A force diagram shows how an instability in body pitch develops. During hovering, the wings flap back and forth to produce lift that balances body weight. A perturbation to the pitch orientation causes the insect to move forwards. Drag on the wings then becomes unbalanced, inducing a torque that tends to tip the insect backwards. This simplified picture highlights some of the important effects to be incorporated in a model of the pitch dynamics. (Online version in colour.)

Mentions: These simulations motivate a simplified physical picture that captures the nature of the instability [7]. As shown in figure 3, the relevant physical mechanisms can be illustrated most simply for normal hovering flight. The wings beat back and forth, the average lift is directed upwards to balance body weight, and drag points horizontally but cancels for the two half-strokes. If pitched forwards, the re-directed lift drives the insect forwards. This leads to a net drag on the wings, because the wing airspeed on the forward sweep is now greater than the airspeed on the backward sweep [28–30]. If the wings are located above the body centre of mass, as is the case for flies and many other insects [31], this drag creates a nose-up pitch torque that rotates the insect. In effect, the insect is flipped backwards by the drag on its wings. If left uncontrolled, this instability rocks the insect back and forth with growing amplitude and ultimately causes it to tumble from the air.Figure 3.


Active and passive stabilization of body pitch in insect flight.

Ristroph L, Ristroph G, Morozova S, Bergou AJ, Chang S, Guckenheimer J, Wang ZJ, Cohen I - J R Soc Interface (2013)

A force diagram shows how an instability in body pitch develops. During hovering, the wings flap back and forth to produce lift that balances body weight. A perturbation to the pitch orientation causes the insect to move forwards. Drag on the wings then becomes unbalanced, inducing a torque that tends to tip the insect backwards. This simplified picture highlights some of the important effects to be incorporated in a model of the pitch dynamics. (Online version in colour.)
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4043156&req=5

RSIF20130237F3: A force diagram shows how an instability in body pitch develops. During hovering, the wings flap back and forth to produce lift that balances body weight. A perturbation to the pitch orientation causes the insect to move forwards. Drag on the wings then becomes unbalanced, inducing a torque that tends to tip the insect backwards. This simplified picture highlights some of the important effects to be incorporated in a model of the pitch dynamics. (Online version in colour.)
Mentions: These simulations motivate a simplified physical picture that captures the nature of the instability [7]. As shown in figure 3, the relevant physical mechanisms can be illustrated most simply for normal hovering flight. The wings beat back and forth, the average lift is directed upwards to balance body weight, and drag points horizontally but cancels for the two half-strokes. If pitched forwards, the re-directed lift drives the insect forwards. This leads to a net drag on the wings, because the wing airspeed on the forward sweep is now greater than the airspeed on the backward sweep [28–30]. If the wings are located above the body centre of mass, as is the case for flies and many other insects [31], this drag creates a nose-up pitch torque that rotates the insect. In effect, the insect is flipped backwards by the drag on its wings. If left uncontrolled, this instability rocks the insect back and forth with growing amplitude and ultimately causes it to tumble from the air.Figure 3.

Bottom Line: Flying insects have evolved sophisticated sensory-motor systems, and here we argue that such systems are used to keep upright against intrinsic flight instabilities.By glueing magnets to fruit flies and perturbing their flight using magnetic impulses, we show that these insects employ active control that is indeed fast relative to the instability.Finally, we extend this framework to unify the control strategies used by hovering animals and also furnish criteria for achieving pitch stability in flapping-wing robots.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, Cornell University, Ithaca, NY 14853, USA. ristroph@cims.nyu.edu

ABSTRACT
Flying insects have evolved sophisticated sensory-motor systems, and here we argue that such systems are used to keep upright against intrinsic flight instabilities. We describe a theory that predicts the instability growth rate in body pitch from flapping-wing aerodynamics and reveals two ways of achieving balanced flight: active control with sufficiently rapid reactions and passive stabilization with high body drag. By glueing magnets to fruit flies and perturbing their flight using magnetic impulses, we show that these insects employ active control that is indeed fast relative to the instability. Moreover, we find that fruit flies with their control sensors disabled can keep upright if high-drag fibres are also attached to their bodies, an observation consistent with our prediction for the passive stability condition. Finally, we extend this framework to unify the control strategies used by hovering animals and also furnish criteria for achieving pitch stability in flapping-wing robots.

Show MeSH
Related in: MedlinePlus