From Bernoulli’s principle to aerial stability: Rapid disturbance rejection mechanism in hovering hummingbirds
Pennsylvania State University
Abstract
Among the most striking acrobatic abilities of hummingbirds is their aerial stability, which is often tested during their high-speed courtship displays, aerial combat, or escape flights, where agility is often constrained by stability. By subjecting hovering hummingbirds to external disturbances, we showed that they robustly reject external torque within 1 wingbeat and regain stability in 3 wingbeats. This rapid response cannot be explained by the active neuromuscular stabilization via alternating the wing motion pattern, which lacked necessary response speed and magnitude. Instead, hummingbirds relied on a passive mechanism intrinsic to flapping flight, named Aero-Inertial Flapping Counter-Torque (Aero-Inertial FCT). FCT is rooted in Bernoulli’s principle that states the quadratic relationship between wing velocity and aerodynamic pressure. To leverage Aero-Inertial FCT, hummingbirds maintained the relative motion of wings and body undisturbed, likely via spinal-level reflex or viscoelasticity of wing musculature for achieving wing-body joint stability. This result underscores the significance of passive or peripheral neural control to whole-body aerial stability for superior locomotor performance.
About the speaker
Dr. Bo Cheng is an Associate Professor of Mechanical Engineering at Penn State. Prior to this, he was a Postdoctoral Research Associate in the School of Mechanical Engineering at Purdue University, where he received his Ph.D. in 2012. He also received his M.S. in Mechanical Engineering from the University of Delaware and B.S. from Control Science & Engineering at Zhejiang University, China. His research interests lie in the broad science and engineering of efficient, robust and agile locomotion in fluids, including animal flight, fish swimming, robot locomotion and learning and biologically inspired fluid dynamics. Working in a highly interdisciplinary field, Dr. Cheng’s work has been published in journals from various disciplines, such as Science, Science Advances, Journal of Fluid Mechanics, Physics of Fluids, IEEE Transaction on Robotics, Proceedings of Royal Society B, Journal of Experimental Biology, and Journal of the Royal Society Interface. His research has been funded by various programs of National Science Foundation (NSF), Army Research Office (ARO), Office of Naval Research (ONR), and Air Force Office of Scientific Research. Dr. Cheng received the NSF CAREER Award in 2016.
