Name: a robotic platform to study the foreflipper of the california sea lion
Uploaded: 2017-01-10T12:30:00
Description: Watch this Scientific Journal Video about A Robotic Platform to Study the Foreflipper of the California Sea Lion at JoVE.com

The authors would like to thank the George Washington University Facilitating Fund for financial support of the project. Mr. Patel is grateful the George Washington University School of Engineering and Applied Science Summer Undergraduate Program in Engineering Research and the Undergraduate Research award for financial support. Finally, we are grateful to the GWU Center for Biomemetics and Bioinspired Engineering (COBRE) for use of facilities controlled by the center.

1. Digitize a Specimen of a Sea Lion Foreflipper
<ol>
	<li>Scan a specimen of a Sea lion foreflipper.
	<ol>
		<li>Obtain a specimen of a sea lion flipper from a deceased individual (Figure 1a). 
		NOTE: In our case, they were obtained from the Smithsonian Zoological Park in Washington, D.C.</li>
		<li>Hang the foreflipper vertically from its base (where the foreflipper attaches to the animal&#39;s body). This both allows the flipper to be straight when scanned, and exposes the entire surface for scanning.</...

<ol>
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M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=From+swimming+to+walking+with+a+salamander+robot+driven+by+a+spinal+cord+model.">From swimming to walking with a salamander robot driven by a spinal cord model.</a> Science. 315 (5817), 1416-1420 (2007).</li><li>Buchholz, J. H., Smits, A. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=On+the+evolution+of+the+wake+structure+produced+by+a+low-aspect-ratio+pitching+panel.">On the evolution of the wake structure produced by a low-aspect-ratio pitching panel.</a> Journal of fluid mechanics. 546, 433-443 (2006).</li><li>Lauder, G. V., Anderson, E. J., Tangorra, J., Madden, P. 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The robotic flipper apparatus will allow us to understand the hydrodynamics of the swimming California sea lion. This includes the basic thrust producing stroke (the &#39;clap&#39;), as well as non-physical variations that animal studies cannot investigate. The robotic flipper has been designed for experimental versatility, thus, step 3&#8212;where the flipper itself is made&#8212;is critical in obtaining the desired results. While this apparatus is, clearly, just a model of the living system, in situ studies of...

While scientists have investigated the basic characteristics of sea lion swimming (energetics, cost of transport, drag coefficient, linear speed and acceleration1-3, we lack information about the fluid dynamics of the system. Without this knowledge, we limit potential high-speed, high-maneuverability engineering applications to body-caudal fin (BCF) locomotion models4. By characterizing a different swimming paradigm, we hope to expand our catalog of design tools, specifically those with the potential to enable quieter, stealthier forms of swimming. Thus, we study the fundamental mechanism of sea lion swimming through direct observation of the California sea lion and laboratory investigations using a robotic sea lion foreflipper5,6 .
To do this, we will employ a commonly used technique for exploring complex biological systems: a robotic platform7. Several locomotion studies&#8212;both of walking8,9 and swimming10&#8212;have been based on either complex11 or highly simplified12 mechanical models of animals. Typically, the robotic platforms retain the essence of the model system, while allowing researchers to explore large parameter spaces13-15. While not always characterizing the entire system, much is learned through these platforms that isolate a single component of a locomotive system. For example, the fundamental functioning of unsteady propulsors, like the back-and-forth sweeping of a caudal fin during carangiform swimming, has been intensely explored through experimental investigations of pitching and/or heaving panels12,16,17,18. In this case, we can isolate certain modes of this complex motion in ways that animal based studies cannot. Those fundamental aspects of propulsion can then be used in the design of vehicles which do not need the biological complexity evolution provides.
In this paper, we present a novel platform for exploring the &#39;clap&#39; phase of the sea lion thrust-producing stroke. Only a single foreflipper&#8212;the &#39;roboflipper&#39;&#8212;is included in the platform. Its geometry is derived exactly from biological scans of a California sea lion (Zalophus californianus) specimen. The roboflipper is actuated to replicate the motion of the animals&#39; derived from previous studies1. This robotic flipper will be used to investigate the hydrodynamic performance of the swimming sea lion and to explore a wider parameter space than animal studies, particularly those of large aquatic mammals, can yield.

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a robotic platform to study the foreflipper of the california sea lion

The California sea lion (Zalophus californianus), is an agile and powerful swimmer. Unlike many successful swimmers (dolphins, tuna), they generate most of their thrust with their large foreflippers. This protocol describes a robotic platform designed to study the hydrodynamic performance of the swimming California sea lion (Zalophus californianus). The robot is a model of the animal&#39;s foreflipper that is actuated by motors to replicate the motion of its propulsive stroke (the &#39;clap&#39;). The kinematics of the sea lion&#39;s propulsive stroke are extracted from video data of unmarked, non-research sea lions at the Smithsonian Zoological Park (SNZ). Those data form the basis of the actuation motion of the robotic flipper presented here. The geometry of the robotic flipper is based a on high-resolution laser scan of a foreflipper of an adult female sea lion, scaled to about 60% of the full-scale flipper. The articulated model has three joints, mimicking the elbow, wrist and knuckle joint of the sea lion foreflipper. The robotic platform matches dynamics properties&#8212;Reynolds number and tip speed&#8212;of the animal when accelerating from rest. The robotic flipper can be used to determine the performance (forces and torques) and resulting flowfields.

The process described above yields a robotic model of a California sea lion foreflipper. The model can be used in two different ways. One is by actuating the flipper only at the root (Figure 6a). In this case, the driving motor sets the rotational rate of the first joint, but the resulting motion of the flipper is determined by the fluid-structure interaction between the flexible flipper and the surrounding water. Additionally, we can create robotic flipp...

Watch this Scientific Journal Video about A Robotic Platform to Study the Foreflipper of the California Sea Lion at JoVE.com

A Robotic Platform to Study the Foreflipper of the California Sea Lion

A robotic platform is described that will be used to study the hydrodynamic performance&#8212;forces and flowfields&#8212;of the swimming California sea lion. The robot is a model of the animal&#39;s foreflipper that is actuated by motors to replicate the motion of its propulsive stroke (the &#39;clap&#39;).

The California sea lion (Zalophus californianus), is an agile and powerful swimmer. Unlike many successful swimmers (dolphins, tuna), they generate most ...

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