A new shape-shifting turtle robot could explore the treacherous regions where land meets sea—and could lead to future machines capable of navigating complex real-world conditions.
The recently described amphibious robotic tortoise (ART) combines the best mobility characteristics of swimming sea turtles and tortoises exist nature, can change its limbs from turtle-like flippers to turtle-like legs. “Most amphibious robots … use dedicated propulsion systems for each environment,” said Yale roboticist Rebecca Kramer-Bottiglio, senior author of the paper. “Our system employs a single unified propulsion mechanism for both environments: it has four limbs that can switch between a flipper state for water locomotion and a leg state for land locomotion.”
Each deformable limb is surrounded by a composite polymer material that is malleable when hot and rigid when cold. To change the shape of the limb, built-in copper heaters heat and soften the outer material. The soft robotic “muscles” underneath then expand or contract, turning the flat flippers into rounded legs and vice versa. Finally, the polymer cools and hardens around the new shape within a minute or two. The soft robotic limbs are connected to more traditional “hard” robotic shoulder joints, which contain three electronic motors so the ART can “crawl” or “crawl” on land, and “paddle” or “slap” in water. These joints connect to the modular chassis, where sealed PVC tubing protects the robot’s electronics from water. The 3D-printed “hull” gives the robot a streamlined shape and a space for air or ballast to adjust buoyancy.
Combining soft robotics and conventional robotics gives ART its translational capabilities, says roboticist Tønnes Nygaard of Oslo Metropolitan University, who did not contribute to the new research. “Very rigid, stiff movement patterns [are] This is required when you use traditional robotics,” he added. “But now with technology like this soft robot, you might be able to do something smoother. “
This adaptive technology could eventually help robots trek across many different surfaces and environments in the real world without having to carry additional propulsion systems that could reduce their efficiency of movement. Kramer-Bottiglio’s team found that ART uses roughly the same energy as a robot built for only one environment.
The robotic turtle isn’t quite there yet: The current prototype still requires a tether for power and communication, and its movements are slow and awkward. But researchers are working to improve these problems. “I’m excited to see how far they’ve come,” Nygaard said. “And I’m curious to see what will come out of this group in a few years.”