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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Bridging two insect flight modes in evolution, physiology and robophysics
Since taking flight, insects have undergone repeated evolutionary transitions between two seemingly distinct flight modes1–3. Some insects neurally activate their muscles synchronously with each wingstroke. However, many insects have achieved wingbeat frequencies beyond the speed limit of typical neuromuscular systems by evolving flight muscles that are asynchronous with neural activation and activate in response to mechanical stretch2–8. These modes reflect the two fundamental ways of generating rhythmic movement: time-periodic forcing versus emergent oscillations from self-excitation8–10. How repeated evolutionary transitions have occurred and what governs the switching between these distinct modes remain unknown. Here we find that, despite widespread asynchronous actuation in insects across the phylogeny3,6, asynchrony probably evolved only once at the order level, with many reversions to the ancestral, synchronous mode. A synchronous moth species, evolved from an asynchronous ancestor, still preserves the stretch-activated muscle physiology. Numerical and robophysical analyses of a unified biophysical framework reveal that rather than a dichotomy, these two modes are two regimes of the same dynamics. Insects can transition between flight modes across a bridge in physiological parameter space. Finally, we integrate these two actuation modes into an insect-scale robot11–13that enables transitions between modes and unlocks a new self-excited wingstroke strategy for engineered flight. Together, this framework accounts for repeated transitions in insect flight evolution and shows how flight modes can flip with changes in physiological parameters.
more » « less- PAR ID:
- 10534216
- Publisher / Repository:
- Nature Publishing Group
- Date Published:
- Journal Name:
- Nature
- Volume:
- 622
- Issue:
- 7984
- ISSN:
- 0028-0836
- Page Range / eLocation ID:
- 767 to 774
- Subject(s) / Keyword(s):
- Insect flight resonance muscle bio-inspired robotics robot evolution
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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null (Ed.)Centimetre-scale fliers must contend with the high power requirements of flapping flight. Insects have elastic elements in their thoraxes which may reduce the inertial costs of their flapping wings. Matching wingbeat frequency to a mechanical resonance can be energetically favourable, but also poses control challenges. Many insects use frequency modulation on long timescales, but wingstroke-to-wingstroke modulation of wingbeat frequencies in a resonant spring-wing system is potentially costly because muscles must work against the elastic flight system. Nonetheless, rapid frequency and amplitude modulation may be a useful control modality. The hawkmoth Manduca sexta has an elastic thorax capable of storing and returning significant energy. However, its nervous system also has the potential to modulate the driving frequency of flapping because its flight muscles are synchronous. We tested whether hovering hawkmoths rapidly alter frequency during perturbations with vortex rings. We observed both frequency modulation (32% around mean) and amplitude modulation (37%) occurring over several wingstrokes. Instantaneous phase analysis of wing kinematics revealed that more than 85% of perturbation responses required active changes in neurogenic driving frequency. Unlike their robotic counterparts that abdicate frequency modulation for energy efficiency, synchronous insects use wingstroke-to-wingstroke frequency modulation despite the power demands required for deviating from resonance.more » « less
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Synopsis The evolution of flight in an early winged insect ancestral lineage is recognized as a key adaptation explaining the unparalleled success and diversification of insects. Subsequent transitions and modifications to flight machinery, including secondary reductions and losses, also play a central role in shaping the impacts of insects on broadscale geographic and ecological processes and patterns in the present and future. Given the importance of insect flight, there has been a centuries-long history of research and debate on the evolutionary origins and biological mechanisms of flight. Here, we revisit this history from an interdisciplinary perspective, discussing recent discoveries regarding the developmental origins, physiology, biomechanics, and neurobiology and sensory control of flight in a diverse set of insect models. We also identify major outstanding questions yet to be addressed and provide recommendations for overcoming current methodological challenges faced when studying insect flight, which will allow the field to continue to move forward in new and exciting directions. By integrating mechanistic work into ecological and evolutionary contexts, we hope that this synthesis promotes and stimulates new interdisciplinary research efforts necessary to close the many existing gaps about the causes and consequences of insect flight evolution.
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1038/s41586-023-06606-3
