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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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Related in: MedlinePlus

Interpreting experiments on fruit flies using the control and stability diagram. Crosses representing different insects are superposed on the diagram of figure 5a. The normal fruit fly is predicted to be intrinsically unstable, and instead relies on reactions that are of the same order as TI or about six times faster than the instability, TINST/TRXN ≈ 6. When the halteres are disabled, the insects are left with slower sensors—such as the visual system—and flight performance is significantly degraded. These same insects can be passively stabilized if damping is increased by attaching fibres to their bodies. (Online version in colour.)
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RSIF20130237F6: Interpreting experiments on fruit flies using the control and stability diagram. Crosses representing different insects are superposed on the diagram of figure 5a. The normal fruit fly is predicted to be intrinsically unstable, and instead relies on reactions that are of the same order as TI or about six times faster than the instability, TINST/TRXN ≈ 6. When the halteres are disabled, the insects are left with slower sensors—such as the visual system—and flight performance is significantly degraded. These same insects can be passively stabilized if damping is increased by attaching fibres to their bodies. (Online version in colour.)

Mentions: To illustrate the utility of the time-scale formulation, we next offer a theoretical interpretation of the experiments. In assessing the flight stability of the fruit fly, we use aerodynamic and morphological parameters and the mean reaction time of TRXN = 13 ms measured in the perturbation experiments to determine that TP/TI = 6.1 and TRXN/TI = 0.93, as indicated by the lower cross in figure 6. These data show that fruit flies experience relatively weak damping and thus are inherently unstable. However, these insects are able to actively control flight because of their fast reactions. Consistent with control theory rules of thumb, we find that fruit flies use reactions that are about six times faster than the instability growth time, which is equivalent to a phase margin near 45°.Figure 6.


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)

Interpreting experiments on fruit flies using the control and stability diagram. Crosses representing different insects are superposed on the diagram of figure 5a. The normal fruit fly is predicted to be intrinsically unstable, and instead relies on reactions that are of the same order as TI or about six times faster than the instability, TINST/TRXN ≈ 6. When the halteres are disabled, the insects are left with slower sensors—such as the visual system—and flight performance is significantly degraded. These same insects can be passively stabilized if damping is increased by attaching fibres to their bodies. (Online version in colour.)
© Copyright Policy - open-access
Related In: Results  -  Collection

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

RSIF20130237F6: Interpreting experiments on fruit flies using the control and stability diagram. Crosses representing different insects are superposed on the diagram of figure 5a. The normal fruit fly is predicted to be intrinsically unstable, and instead relies on reactions that are of the same order as TI or about six times faster than the instability, TINST/TRXN ≈ 6. When the halteres are disabled, the insects are left with slower sensors—such as the visual system—and flight performance is significantly degraded. These same insects can be passively stabilized if damping is increased by attaching fibres to their bodies. (Online version in colour.)
Mentions: To illustrate the utility of the time-scale formulation, we next offer a theoretical interpretation of the experiments. In assessing the flight stability of the fruit fly, we use aerodynamic and morphological parameters and the mean reaction time of TRXN = 13 ms measured in the perturbation experiments to determine that TP/TI = 6.1 and TRXN/TI = 0.93, as indicated by the lower cross in figure 6. These data show that fruit flies experience relatively weak damping and thus are inherently unstable. However, these insects are able to actively control flight because of their fast reactions. Consistent with control theory rules of thumb, we find that fruit flies use reactions that are about six times faster than the instability growth time, which is equivalent to a phase margin near 45°.Figure 6.

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