Showing papers on "Aquatic locomotion published in 2012"
TL;DR: This work focuses on a key subset of the knifefish's omnidirectional mechanical abilities: hovering in place, and swimming forward at variable speed, and suggests hypotheses regarding the fin's neural control.
Abstract: Weakly electric knifefish are exceptionally maneuverable swimmers. In prior work, we have shown that they are able to move their entire body omnidirectionally so that they can rapidly reach prey up to several centimeters away. Consequently, in addition to being a focus of efforts to understand the neural basis of sensory signal processing in vertebrates, knifefish are increasingly the subject of biomechanical analysis to understand the coupling of signal acquisition and biomechanics. Here, we focus on a key subset of the knifefish's omnidirectional mechanical abilities: hovering in place, and swimming forward at variable speed. Using high-speed video and a markerless motion capture system to capture fin position, we show that hovering is achieved by generating two traveling waves, one from the caudal edge of the fin and one from the rostral edge, moving toward each other. These two traveling waves overlap at a nodal point near the center of the fin, cancelling fore–aft propulsion. During forward swimming at low velocities, the caudal region of the fin continues to have counter-propagating waves, directly retarding forward movement. The gait transition from hovering to forward swimming is accompanied by a shift in the nodal point toward the caudal end of the fin. While frequency varies significantly to increase speed at low velocities, beyond approximately one body length per second, the frequency stays near 10 Hz, and amplitude modulation becomes more prominent. A coupled central pattern generator model is able to reproduce qualitative features of fin motion and suggest hypotheses regarding the fin's neural control.
59 citations
TL;DR: Overall, X. mucosus makes slight modifications to its efficient swimming locomotion mechanics, principally by increasing movement of the tail, to move effectively over the terrestrial environment.
Abstract: Several taxa of marine fishes are capable of both aquatic and terrestrial locomotion, yet the terrestrial locomotion mechanics of many of these taxa have not been studied. Many species of the prickleback family Stichaeidae, including the Rock Prickleback, Xiphister mucosus, are capable of both aquatic and terrestrial locomotion. In this study, high-speed video was used to compare the mechanics of aquatic and terrestrial locomotion of X. mucosus. While swimming, tail-beats occur faster, and the velocities of the head and tail are greater than on land. On land, tail-beats are slower and cover a longer distance, yet the distance traveled by the head is similar to the distance traveled during aquatic locomotion. Froude propulsion efficiencies during swimming average 0.75 (s = 0.05) indicating efficient swimming mechanics in X. mucosus. These efficiency values are typical for other anguilliform swimmers that make terrestrial excursions. Overall, X. mucosus makes slight modifications to its efficient...
13 citations
30 Nov 2012
TL;DR: In this article, the authors analyzed swimming motions of living swimming organisms in nature for applying them into the swimming motion of a robot leg and found considerable similarity in the result of trajectory and joint angles comparison.
Abstract: In these days, researches about underwater robots have been actively in progress for the purposes of ocean detection and resource exploration. Unlike general underwater robots such as ROV(Remotely Operated Vehicle) and AUV(Autonomous Underwater Vehicle) which have propellers, an articulated underwater robot which is called Crabster has been being developed in KORDI(Korea Ocean Research & Development Institute) with many cooperation organizations since 2010. The robot is expected to be able to walk and swim under the sea with its legs. Among many researching fields of this project, we are focusing on a swimming section. In order to find effective swimming locomotion for the robot, we approached this subject in terms of Biomimetics. As a model of optimized swimming organism in nature, diving beetles were chosen. In the paper, swimming motions of diving beetles were analyzed in viewpoint of robotics for applying them into the swimming motion of the robot. After modeling the kinematics of diving beetle through robotics engineering technique, we obtained swimming patterns of the one of living diving beetles, and then compared them with calculated optimal swimming patterns of a robot leg. As the first trial to compare the locomotion data of legs of the diving beetle with a robot leg, we have sorted two representative swimming patterns such as forwarding and turning. Experimental environment has been set up to get the motion data of diving beetles. The experimental equipment consists of a transparent aquarium and a high speed camera. Various swimming motions of diving beetles were recorded with the camera. After classifying swimming patterns of the diving beetle, we can get angular data of each joint on hind legs by image processing software, Image J. The data were applied to an optimized algorithm for swimming of a robot leg which was designed by robotics engineering technique. Through this procedure, simulated results which show trajectories of a robot leg were compared with trajectories of a leg of a diving beetle in desired directions. As a result, we confirmed considerable similarity in the result of trajectory and joint angles comparison.
4 citations