Flapping Wings Amplify Pitch Stability: Insights from a Robotic Bird

Fuente: arXiv
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Autori principali: Gissler, Rónán, Breuer, Kenneth S.
Natura: Preprint
Pubblicazione: 2026
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author Gissler, Rónán
Breuer, Kenneth S.
author_facet Gissler, Rónán
Breuer, Kenneth S.
contents Using a flapping robot in a wind tunnel, we show that flapping faster amplifies existing longitudinal static stability (focusing on the pitch stiffness) and can even make an unstable flier stable. We show that stability for a flapper is not just a function of the static margin, but also the Strouhal number (St). Experimental data from measurements over a wide range of frequencies and wind speeds show good agreement with a quasi-steady blade-element (QSBE) model and a low-order approximation of the QSBE model. The increase in pitch stiffness at higher St can primarily be explained by the increase in the mean effective wind speed. If wingbeat amplitude was allowed to vary, the model suggests that the pitch stiffness would increase with amplitude at high St but decrease with amplitude at low St. Despite using simplified wingbeat kinematics and a restricted analysis of stability, these results provide insight into how altering wingbeat kinematics can affect the passive stability of flying animals and ornithopters.
format Preprint
id arxiv_https___arxiv_org_abs_2604_23359
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Flapping Wings Amplify Pitch Stability: Insights from a Robotic Bird
Gissler, Rónán
Breuer, Kenneth S.
Fluid Dynamics
Using a flapping robot in a wind tunnel, we show that flapping faster amplifies existing longitudinal static stability (focusing on the pitch stiffness) and can even make an unstable flier stable. We show that stability for a flapper is not just a function of the static margin, but also the Strouhal number (St). Experimental data from measurements over a wide range of frequencies and wind speeds show good agreement with a quasi-steady blade-element (QSBE) model and a low-order approximation of the QSBE model. The increase in pitch stiffness at higher St can primarily be explained by the increase in the mean effective wind speed. If wingbeat amplitude was allowed to vary, the model suggests that the pitch stiffness would increase with amplitude at high St but decrease with amplitude at low St. Despite using simplified wingbeat kinematics and a restricted analysis of stability, these results provide insight into how altering wingbeat kinematics can affect the passive stability of flying animals and ornithopters.
title Flapping Wings Amplify Pitch Stability: Insights from a Robotic Bird
topic Fluid Dynamics
url https://arxiv.org/abs/2604.23359