title: Falling with Style: Bats Perform Complex Aerial Rotations by Adjusting Wing Inertia.
abstract: The remarkable maneuverability of flying animals results from precise movements of their highly specialized wings. Bats have evolved an impressive capacity to control their flight, in large part due to their ability to modulate wing shape, area, and angle of attack through many independently controlled joints. Bat wings, however, also contain many bones and relatively large muscles, and thus the ratio of bats' wing mass to their body mass is larger than it is for all other extant flyers. Although the inertia in bat wings would typically be associated with decreased aerial maneuverability, we show that bat maneuvers challenge this notion. We use a model-based tracking algorithm to measure the wing and body kinematics of bats performing complex aerial rotations. Using a minimal model of a bat with only six degrees of kinematic freedom, we show that bats can perform body rolls by selectively retracting one wing during the flapping cycle. We also show that this maneuver does not rely on aerodynamic forces, and furthermore that a fruit fly, with nearly massless wings, would not exhibit this effect. Similar results are shown for a pitching maneuver. Finally, we combine high-resolution kinematics of wing and body movements during landing and falling maneuvers with a 52-degree-of-freedom dynamical model of a bat to show that modulation of wing inertia plays the dominant role in reorienting the bat during landing and falling maneuvers, with minimal contribution from aerodynamic forces. Bats can, therefore, use their wings as multifunctional organs, capable of sophisticated aerodynamic and inertial dynamics not previously observed in other flying animals. This may also have implications for the control of aerial robotic vehicles.
authors.affiliation: School of Engineering, Brown University, Providence, Rhode Island, United States of America.
authors.forename: Attila J
authors.initials: AJ
authors.lastname: Bergou
authors.affiliation: School of Engineering, Brown University, Providence, Rhode Island, United States of America.|Department of Ecology and Evolutionary Biology, Brown University, Providence, Rhode Island, United States of America.
authors.forename: Sharon M
authors.initials: SM
authors.lastname: Swartz
authors.affiliation: School of Engineering, Brown University, Providence, Rhode Island, United States of America.
authors.forename: Hamid
authors.initials: H
authors.lastname: Vejdani
authors.affiliation: Department of Ecology and Evolutionary Biology, Brown University, Providence, Rhode Island, United States of America.
authors.forename: Daniel K
authors.initials: DK
authors.lastname: Riskin
authors.affiliation: Department of Ecology and Evolutionary Biology, Brown University, Providence, Rhode Island, United States of America.
authors.forename: Lauren
authors.initials: L
authors.lastname: Reimnitz
authors.affiliation: School of Engineering, Brown University, Providence, Rhode Island, United States of America.
authors.forename: Gabriel
authors.initials: G
authors.lastname: Taubin
authors.affiliation: School of Engineering, Brown University, Providence, Rhode Island, United States of America.|Department of Ecology and Evolutionary Biology, Brown University, Providence, Rhode Island, United States of America.
authors.forename: Kenneth S
authors.initials: KS
authors.lastname: Breuer
mesh_terms: D000465:Algorithms; D000818:Animals; D001522:Behavior, Animal; D001696:Biomechanical Phenomena; D001835:Body Weight; D002685:Chiroptera / Q000502:physiology*; D005426:Flight, Animal; D021621:Imaging, Three-Dimensional; D008953:Models, Anatomic; D009929:Organ Size; D015203:Reproducibility of Results; D013045:Species Specificity; D014741:Video Recording; D014921:Wings, Animal / Q000033:anatomy & histology / Q000502:physiology*