A seal with a heavy body and small flippers rises from the water the least gracefully. But despite their appearance, robots that mimic fluttering on dry land could be effective in search-and-rescue operations, where wheeled robots struggle, the team said.
Dimuthu Kodippili Arachchige and his colleagues at DePaul University in Chicago describe how pinnipeds, such as seals and sea lions, bounce and lunge on land, pushing the ground with their flippers while moving their heads and bodies to gain momentum. I created a robot that emulates the
The robot consists of four identical limbs, each 24 cm long and 4 cm in diameter. Each limb he has is made of three silicone tubes that harden when filled with liquid and soften when drained, all covered with a hard plastic skin. By selectively filling one or more tubes, the robot can steer each limb in any direction.
In our experiments, the robot was able to move forward at about 12 centimeters per second, but was able to retreat, reaching about 17 centimeters per second.
All limbs are identical, which makes the robot more adaptable, Arachchige said, but its low mass and different placement make it struggle to mimic the movements of a seal.
“Most of the seal’s weight is concentrated in the rear of its body, but the even distribution of the robot’s weight makes it difficult to move forward while standing upright,” he says. “Conversely, when the robot is moving backwards, the robot’s body helps maintain balance by counteracting the torque generated by that movement.”
The way a real seal rolls by bouncing or leaning sideways also doesn’t work well for a robot, which turns more effectively while moving backwards.
Nevertheless, Arachchige has resisted simply putting the back of the robot forward. That way the robot can move faster and turn while moving forward. “When you put the back in front, the robot doesn’t look like a pinniped,” he says.
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