Robotics

Robotic sea lion flippers could propel future submersibles

Robotic sea lion flippers could propel future submersibles
Prof. Megan Leftwich (upper right) and colleagues observe sea lions at the at the National Zoo in Washington DC
Prof. Megan Leftwich (upper right) and colleagues observe sea lions at the at the National Zoo in Washington DC
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Prof. Megan Leftwich (upper right) and colleagues observe sea lions at the at the National Zoo in Washington DC
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Prof. Megan Leftwich (upper right) and colleagues observe sea lions at the at the National Zoo in Washington DC
Prof. Megan Leftwich (left) with the plastic skeleton of the robotic flipper
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Prof. Megan Leftwich (left) with the plastic skeleton of the robotic flipper

Unlike most other sea creatures, sea lions use their forelimbs instead of a tail for propulsion. They also leave virtually no wake as they travel through the water. With an eye towards applying this design to human technology, George Washington University professor of mechanical and aerospace engineering Megan Leftwich has developed a robotic sea lion flipper.

Leftwich and colleagues started by videotaping swimming sea lions at the Smithsonian's National Zoo. Then, on a frame-by-frame basis, they digitally plotted the relative positions of each flipper's shoulder, elbow and wrist joints as they went through their range of motion. What they discovered was that as the sea lions clap their flippers in towards their body, the trapped water shoots back in a jet, propelling the animals quickly and silently forward.

Based on the joint positions plotted from the video, the scientists proceeded to create an articulated robotic plastic arm (seen below) that moves in the same fashion as a sea lion flipper. Leftwich then performed a 3D scan of an actual flipper, and used it to 3D-print a silicone covering for that arm.

Prof. Megan Leftwich (left) with the plastic skeleton of the robotic flipper
Prof. Megan Leftwich (left) with the plastic skeleton of the robotic flipper

The "skin"-covered arm was subsequently subjected to flow diagnostic techniques to study the effects that skin wrinkles and hairs may have on drag, as well as to establish how much force is required to move such a flipper through the water.

Leftwich is now planning on testing the robotic flipper alongside actual sea lions, in an enclosure at the SLEWTHS (Science, Learning and Education With The Help of Sea Lions) teaching aquarium in California.

Ultimately, it is hoped that the research could lead to designs for stealthy and efficient roboflipper-propelled underwater vehicles.

Source: The George Washington University

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Stephen N Russell
Have subs dual proppelled IE ducted hydro screws & flippers or Red Oct EM Force drive. Larger sub types only