In most instances, flapping wing robots have
emulated the “synchronous” actuation of insects in which the
wingbeat timing is generated from a time-dependent, rhythmic
signal. The internal dynamics of asynchronous insect flight
muscle enable high-frequency, adaptive wingbeats with minimal
direct neural control. In this paper, we investigate how
the delayed stretch-activation (dSA) response of asynchronous
insect flight muscle can be transformed into a feedback control
law for flapping wing robots that results in stable limit cycle
wingbeats. We first demonstrate - in theory and simulation -
the mechanism by which asynchronous wingbeats self-excite.
Then, we implement the feedback law on a dynamically-scaled
robophysical model as well as on an insect-scale robotic flapping
wing. Experiments on large- and small-scale robots demonstrate
good agreement with the theory results and highlight how
dSA parameters govern wingbeat amplitude and frequency.
Lastly, we demonstrate that asynchronous actuation has several
advantages over synchronous actuation schemes, including the
ability to rapidly adapt or halt wingbeats in response to external
loads or collisions through low-level feedback control.
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Dimensional analysis of spring-wing systems reveals performance metrics for resonant flapping-wing flight
Flapping-wing insects, birds and robots are thought to offset the high power cost of oscillatory wing motion by using elastic elements for energy storage and return. Insects possess highly resilient elastic regions in their flight anatomy that may enable high dynamic efficiency. However, recent experiments highlight losses due to damping in the insect thorax that could reduce the benefit of those elastic elements. We performed experiments on, and simulations of, a dynamically scaled robophysical flapping model with an elastic element and biologically relevant structural damping to elucidate the roles of body mechanics, aerodynamics and actuation in spring-wing energetics. We measured oscillatory flapping-wing dynamics and energetics subject to a range of actuation parameters, system inertia and spring elasticity. To generalize these results, we derive the non-dimensional spring-wing equation of motion and present variables that describe the resonance properties of flapping systems: N , a measure of the relative influence of inertia and aerodynamics, and K ^ , the reduced stiffness. We show that internal damping scales with N , revealing that dynamic efficiency monotonically decreases with increasing N . Based on these results, we introduce a general framework for understanding the roles of internal damping, aerodynamic and inertial forces, and elastic structures within all spring-wing systems.
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- Award ID(s):
- 1806833
- NSF-PAR ID:
- 10282871
- Date Published:
- Journal Name:
- Journal of The Royal Society Interface
- Volume:
- 18
- Issue:
- 175
- ISSN:
- 1742-5662
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1098/rsif.2020.0888
