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Stanton SC. Shoulder viscoelasticity in a raptor-inspired model alleviates instability and enhances passive gust rejection. BIOINSPIRATION & BIOMIMETICS 2024; 19:046006. [PMID: 38663419 DOI: 10.1088/1748-3190/ad43a2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2024] [Accepted: 04/25/2024] [Indexed: 05/12/2024]
Abstract
Recent experiments with gliding raptors reveal a perplexing dichotomy: remarkably resilient gust rejection, but, at the same time, an exceptionally high degree of longitudinal instability. To resolve this incompatibility, a multiple degree of freedom model is developed with minimal requisite complexity to examine the hypothesis that the bird shoulder joint may embed essential stabilizing and preflexive mechanisms for rejecting rapid perturbations while simplifying and reducing control effort. Thus, the formulation herein is centrally premised upon distinct wing pitch and body pitch angles coupled via a Kelvin-Voigt viscoelastic shoulder joint. The model accurately exhibits empirical gust response of an unstable gliding raptor, generates biologically plausible equilibrium configurations, and the viscoelastic shoulder coupling is shown to drastically alleviate the high degree of instability predicted by conventional linear flight dynamics models. In fact, stability analysis of the model predicts a critical system timescale (the time to double amplitude of a pitch divergence mode) that is commensurate within vivomeasured latency of barn owls (Tyto alba). Active gust mitigation is studied by presupposing the owl behaves as an optimal controller. The system is under-actuated and the feedback control law is resolved in the controllable subspace using a Kalman decomposition. Importantly, control-theoretic analysis precisely identifies what discrete gust frequencies may be rapidly and passively rejected versus disturbances requiring feedback control intervention.
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Affiliation(s)
- Samuel C Stanton
- Department of Aeronautics, United States Air Force Academy, Springs, Colorado, CO, United States of America
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Macaulay S, Hoehfurtner T, Cross SRR, Marek RD, Hutchinson JR, Schachner ER, Maher AE, Bates KT. Decoupling body shape and mass distribution in birds and their dinosaurian ancestors. Nat Commun 2023; 14:1575. [PMID: 36949094 PMCID: PMC10033513 DOI: 10.1038/s41467-023-37317-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Accepted: 03/13/2023] [Indexed: 03/24/2023] Open
Abstract
It is accepted that non-avian theropod dinosaurs, with their long muscular tails and small forelimbs, had a centre-of-mass close to the hip, while extant birds, with their reduced tails and enlarged wings have their mass centred more cranially. Transition between these states is considered crucial to two key innovations in the avian locomotor system: crouched bipedalism and powered flight. Here we use image-based models to challenge this dichotomy. Rather than a phylogenetic distinction between 'dinosaurian' and 'avian' conditions, we find terrestrial versus volant taxa occupy distinct regions of centre-of-mass morphospace consistent with the disparate demands of terrestrial bipedalism and flight. We track this decoupled evolution of body shape and mass distribution through bird evolution, including the origin of centre-of-mass positions more advantageous for flight and major reversions coincident with terrestriality. We recover modularity in the evolution of limb proportions and centre-of-mass that suggests fully crouched bipedalism evolved after powered flight.
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Affiliation(s)
- Sophie Macaulay
- Department of Musculoskeletal & Ageing Science, Institute of Life Course & Medical Sciences, University of Liverpool, William Henry Duncan Building, 6 West Derby Street, Liverpool, L7 8TX, UK
| | - Tatjana Hoehfurtner
- Department of Musculoskeletal & Ageing Science, Institute of Life Course & Medical Sciences, University of Liverpool, William Henry Duncan Building, 6 West Derby Street, Liverpool, L7 8TX, UK
- Department of Life Sciences, School of Life Sciences, University of Lincoln, Joseph Banks Laboratories, Green Lane, Lincoln, LN6 7DL, UK
| | - Samuel R R Cross
- Department of Musculoskeletal & Ageing Science, Institute of Life Course & Medical Sciences, University of Liverpool, William Henry Duncan Building, 6 West Derby Street, Liverpool, L7 8TX, UK
| | - Ryan D Marek
- Department of Cell & Development Biology, Division of Biosciences, University College London, Anatomy Building, Gower Street, London, WC1E 6BT, UK
| | - John R Hutchinson
- Structure and Motion Laboratory, Department of Comparative Biomedical Sciences, Royal Veterinary College, Hatfield, AL9 7TA, UK
| | - Emma R Schachner
- Department of Cell Biology and Anatomy, School of Medicine, Louisiana State University Health Sciences Center, New Orleans, LA, 70112, USA
| | - Alice E Maher
- Department of Musculoskeletal & Ageing Science, Institute of Life Course & Medical Sciences, University of Liverpool, William Henry Duncan Building, 6 West Derby Street, Liverpool, L7 8TX, UK
| | - Karl T Bates
- Department of Musculoskeletal & Ageing Science, Institute of Life Course & Medical Sciences, University of Liverpool, William Henry Duncan Building, 6 West Derby Street, Liverpool, L7 8TX, UK.
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Fath MA, Nguyen SV, Donahue J, McMenamin SK, Tytell ED. Static Stability and Swim Bladder Volume in the Bluegill Sunfish ( Lepomis macrochirus). Integr Org Biol 2023; 5:obad005. [PMID: 36910303 PMCID: PMC10002887 DOI: 10.1093/iob/obad005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2022] [Revised: 12/20/2022] [Indexed: 02/17/2023] Open
Abstract
Static stability is a property inherent to every organism. More stable bodies benefit from a lower energy cost associated with maintaining a desired orientation, while less stable bodies can be more maneuverable. The static stability of a fish is determined by the relative locations of its center of mass (COM) and center of buoyancy (COB), which may change with changes in swim bladder volume. We hypothesized, however, that fish would benefit from consistent static stability, and predicted that changes in swim bladder volume would not alter the overall pattern of COM and COB locations. We used micro-computed tomography to estimate the locations of the COM and COB in bluegill sunfish (Lepomis macrochirus). Using this technique, we were able to find a small but significant difference between the location of the COM and COB for a given orientation. We found that the swim bladder can change shape within the body cavity, changing relative locations of the COM and COB. At one extreme, the COB is located 0.441 ± 0.007 BL from the snout and 0.190 ± 0.010 BL from the ventral surface of the pelvic girdle, and that the COM is 0.0030 ± 0.0020 BL posterior and 0.0006 ± 0.0005 BL ventral to the COB, a pattern that causes a nose-up pitching torque. At the other extreme, the COM is anterior and dorsal to the COB, a pattern that causes the opposite torque. These changes in location seems to be caused by changes in the shape and centroid location of the swim bladder within the body: The centroid of the swim bladder is located significantly more posteriorly in fish oriented head-down. The air in the bladder "rises" while heavier tissues "sink," driving a change in tissue distribution and changing the location of the COM relative to the COB. Supporting our hypothesis, we found no correlation between swim bladder volume and the distance between the COM and COB. We conclude that bluegill are statically unstable, requiring them to expend energy constantly to maintain their normal orientation, but that the pitch angle of the body could alter the relative locations of COM and COB, changing their static stability.
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Affiliation(s)
- M A Fath
- Department of Biology, Tufts University, 200 Boston Avenue, Suite 4700, Medford, MA 02155, USA
| | - S V Nguyen
- Department of Biology, Boston College, 24 Cummington Mall #606, Boston, MA 02215, USA
| | - J Donahue
- Department of Biology, Boston College, 24 Cummington Mall #606, Boston, MA 02215, USA
| | - S K McMenamin
- Department of Biology, Boston College, 24 Cummington Mall #606, Boston, MA 02215, USA
| | - E D Tytell
- Department of Biology, Tufts University, 200 Boston Avenue, Suite 4700, Medford, MA 02155, USA
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