Decision and Control Lecture Series

Decision and Control Laboratory, Coordinated Science Laboratory

Antagonistic thrust forces enhance controllability and stability at the expense of energy in the glass knifefish

Noah J. Cowan

Associate Professor, Department of Mechanical Engineering

Johns Hopkins University

Wednesday, February 13, 2013

3:00 p.m. to 4:00 p.m.

B02 Auditorium CSL

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Abstract

A key insight of the Wright brothers was that an aircraft must be both sufficiently stable to maintain its flight path and simultaneously maneuverable enough to permit its control. This tradeoff between stability and maneuverability is a critical engineering problem for the design of airborne and submarine vessels. Many swimming and flying animals, however, appear to fly or swim using locomotor strategies that are extremely stable and yet facilitate the control of extraordinary maneuvers. We wondered how animals might mitigate the tradeoff between stability and maneuverability, and studied the glass knifefish, Eigenmannia virescens, that swims using counter-propagating traveling waves with its ventral ribbon fin. The agile knifefish dynamically partitions its long undulatory ribbon fin into two inward-counter-propagating waves. Traveling waves originate from the front and back of the fin and collide at a nodal point. Rapid neural control of the position of the nodal point causes correspondingly rapid changes in fore--aft force. We analyzed this strategy and implemented it in a robotic submarine and found that counter-propagating waves result in enhanced stabilizing forces and increased maneuverability by reducing the control effort required to change direction compared to using a single traveling wave.

Biography

Noah J. Cowan received a B.S. degree from the Ohio State University, Columbus, in 1995, and M.S. and Ph.D. degrees from the University of Michigan, Ann Arbor, in 1997 and 2001 – all in electrical engineering. Following his Ph.D., he was a Postdoctoral Fellow in Integrative Biology at the University of California, Berkeley for 2 years. In 2003, he joined the mechanical engineering department at Johns Hopkins University, Baltimore, MD, where he is now an Associate Professor. Prof. Cowan's research interests include mechanics and multisensory control in animals and machines. Prof. Cowan received the NSF PECASE award in 2010, the James S. McDonnell Foundation Scholar Award in Complex Systems in 2012, and the William H. Huggins Award for excellence in teaching in 2004

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