Free Flight Testing and Performance Evaluation of a Passively Morphing Ornithopter

Wissa, Aimy; Grauer, Jared A.; Guerreiro, Nelson; Hubbard, James E.; Altenbuchner, Cornelia; Tummala, Yashwanth; Frecker, Mary; Roberts, Rodney G.

doi:10.1260/1756-8293.7.1.21

Cited by 14 publications

(14 citation statements)

References 24 publications

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“…This not only revises our textbook understanding of avian functional morphology [5,6,19], but may critically inform fossil interpretation [29] and developmental studies [22,23]. Finally, the six-bar model offers the first quantitative information for avian-inspired morphing wing design [30][31][32][33].…”

Section: Introductionmentioning

confidence: 68%

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How pigeons couple three-dimensional elbow and wrist motion to morph their wings

Stowers

Matloff

Lentink³

2017

J. R. Soc. Interface.

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Birds change the shape and area of their wings to an exceptional degree, surpassing insects, bats and aircraft in their ability to morph their wings for a variety of tasks. This morphing is governed by a musculoskeletal system, which couples elbow and wrist motion. Since the discovery of this effect in 1839, the planar 'drawing parallels' mechanism has been used to explain the coupling. Remarkably, this mechanism has never been corroborated from quantitative motion data. Therefore, we measured how the wing skeleton of a pigeon () moves during morphing. Despite earlier planar assumptions, we found that the skeletal motion paths are highly three-dimensional and do not lie in the anatomical plane, ruling out the 'drawing parallels' mechanism. Furthermore, micro-computed tomography scans in seven consecutive poses show how the two wrist bones contribute to morphing, particularly the sliding ulnare. From these data, we infer the joint types for all six bones that form the wing morphing mechanism and corroborate the most parsimonious mechanism based on least-squares error minimization. Remarkably, the algorithm shows that all optimal four-bar mechanisms either lock, are unable to track the highly three-dimensional bone motion paths, or require the radius and ulna to cross for accuracy, which is anatomically unrealistic. In contrast, the algorithm finds that a six-bar mechanism recreates the measured motion accurately with a parallel radius and ulna and a sliding ulnare. This revises our mechanistic understanding of how birds morph their wings, and offers quantitative inspiration for engineering morphing wings.

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Section: Introductionmentioning

confidence: 68%

“…crossed four-bar model offer quantitative inspiration for engineering morphing wing design [30][31][32][33].…”

mentioning

confidence: 99%

How pigeons couple three-dimensional elbow and wrist motion to morph their wings

Stowers

Matloff

Lentink³

2017

J. R. Soc. Interface.

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“…Bats perform less well than high-performance birds, in several metrics, but they are mostly on par with pigeons [159]. Data for scoring from [14,141,[159][160][161][162][163].…”

Section: Robotic Kinematics and Performancementioning

confidence: 99%

Inspiration for wing design: how forelimb specialization enables active flight in modern vertebrates

Chin¹,

Matloff²,

Stowers³

et al. 2017

J. R. Soc. Interface.

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Harnessing flight strategies refined by millions of years of evolution can help expedite the design of more efficient, manoeuvrable and robust flying robots. This review synthesizes recent advances and highlights remaining gaps in our understanding of how bird and bat wing adaptations enable effective flight. Included in this discussion is an evaluation of how current robotic analogues measure up to their biological sources of inspiration. Studies of vertebrate wings have revealed skeletal systems well suited for enduring the loads required during flight, but the mechanisms that drive coordinated motions between bones and connected integuments remain ill-described. Similarly, vertebrate flight muscles have adapted to sustain increased wing loading, but a lack of in vivo studies limits our understanding of specific muscular functions. Forelimb adaptations diverge at the integument level, but both bird feathers and bat membranes yield aerodynamic surfaces with a level of robustness unparalleled by engineered wings. These morphological adaptations enable a diverse range of kinematics tuned for different flight speeds and manoeuvres. By integrating vertebrate flight specializationsparticularly those that enable greater robustness and adaptability-into the design and control of robotic wings, engineers can begin narrowing the wide margin that currently exists between flying robots and vertebrates. In turn, these robotic wings can help biologists create experiments that would be impossible in vivo.

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“…The solid spar configuration served as a baseline for the ornithopter structure, as well as to determine suitable values for the spar properties such as modulus of elasticity and structural damping coefficient. The CCM designs were based on a compliant spine featuring two compliant joints, which has been tested previously (COMP04PM) [10,32,33]. CSA has the same design parameters and dimensions as the previously tested compliant spine, and CSB has the same design parameters but has been shortened to reduce the mass, and thereby reducing the rotational inertia penalty.…”

Section: Configurations Fabricated For Experiments Andmentioning

confidence: 99%

“…CSB was placed at 40% of the distance. The 40% location is based on the insertion location during the previous benchtop and free flight experiments using COMP04PM [10,33], and was chosen previously based on the location of a typical bird elbow joint (40% of the half wingspan).…”

Section: Configurations Fabricated For Experiments Andmentioning

confidence: 99%

Tuning of a Rigid-Body Dynamics Model of a Flapping Wing Structure With Compliant Joints

Calogero

Frecker

Hasnain

et al. 2017

Journal of Mechanisms and Robotics

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A method for validating rigid-body models of compliant mechanisms under dynamic loading conditions using motion tracking cameras and genetic algorithms is presented. The compliant mechanisms are modeled using rigid-body mechanics as compliant joints (CJ): spherical joints with distributed mass and three-axis torsional spring dampers. This allows compliant mechanisms to be modeled using computationally efficient rigid-body dynamics methods, thereby allowing a model to determine the desired stiffness and location characteristics of compliant mechanisms spatially distributed into a structure. An experiment was performed to validate a previously developed numerical dynamics model with the goal of tuning unknown model parameters to match the flapping kinematics of the leading edge spar of an ornithopter with contact-aided compliant mechanisms (CCMs), compliant mechanisms that feature self-contact to produce nonlinear stiffness, inserted. A system of computer motion tracking cameras was used to record the kinematics of reflective tape and markers placed along the leading edge spar with and without CCMs inserted. A genetic algorithm was used to minimize the error between the model and experimental marker kinematics. The model was able to match the kinematics of all markers along the spars with a root-mean-square error (RMSE) of less than 2% of the half wingspan over the flapping cycle. Additionally, the model was able to capture the deflection amplitude and harmonics of the CCMs with a RMSE of less than 2 deg over the flapping cycle.

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Free Flight Testing and Performance Evaluation of a Passively Morphing Ornithopter

Cited by 14 publications

References 24 publications

How pigeons couple three-dimensional elbow and wrist motion to morph their wings

How pigeons couple three-dimensional elbow and wrist motion to morph their wings

Inspiration for wing design: how forelimb specialization enables active flight in modern vertebrates

Tuning of a Rigid-Body Dynamics Model of a Flapping Wing Structure With Compliant Joints

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