Yale researchers create a new amphibious turtle robot with shape-shifting limbs

The uses of such a robot include ocean farming, diver support, and monitoring of coastal ecosystems.
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The limbs change shape when moving from one environment to another using material with varying stiffness and artificial muscles.
The limbs change shape when moving from one environment to another using material with varying stiffness and artificial muscles.

Yale University 

Yale University researchers in the U.S. have developed a new amphibious turtle robot that has the ability to transform its legs into flippers.

The amphibious robotic turtle, known as ART (Amphibious Robotic Turtle), was inspired by the land and aquatic turtles, a group whose fossil record dates back over 110 million years, according to a press release published by the university on Wednesday.

"Terrestrial and aquatic turtles share similar bodies, with four limbs and a shell, but have distinctive limb shapes and gaits adapted for their specific environment," said Rebecca Kramer-Bottiglio, the John J. Lee Associate Professor of Mechanical Engineering & Materials Science and principal investigator of the study.

"Sea turtles have elongated flippers for swimming, whereas land turtles and tortoises have rounded legs for load bearing while walking."

Shape-shifting limbs

The robot has morphing limbs that may change shape, stiffness, and behavior depending on the surrounding conditions.

The limbs change shape when moving from one environment to another using material with varying stiffness and artificial muscles.

ART may move around the ground with a variety of four-legged terrestrial gaits while it is on its legs. It can transform its legs into flippers once it is near a body of water, allowing it to swim with lift- and drag-based aquatic gaits.

"You can almost think of [adaptive morphogenesis] as a form of evolution on demand," wrote Karl Ziemelis, the chief physical sciences editor for Nature journal.

The robot differentiates from existing amphibious robots by using form adaptation to employ the same elements for propulsion in both water and land conditions.

In other methods, the same robot is given various propulsive systems, each of which is used in a distinct environment, which might result in energy inefficiencies.

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"Our results show that adaptive morphogenesis can enhance the efficiency of robots that locomote through multiple environments," said Kramer-Bottiglio.

What is the use of such a robot?

There are a lot of potential uses of the turtle- and tortoise-inspired amphibious robot.

The applications that Kramer-Bottiglio's lab has concentrated on include ocean farming, diver support, and monitoring of coastal ecosystems.

The robot will also assist researchers in their study of the mechanics of mobility in various environmental transition zones as well as the challenging surf zone, where waves, currents, and turbidity provide unique challenges for robotic systems.

Robert Baines, Sree Kalyan Patiballa, Joran Booth, Luis Ramirez, Thomas Sipple, and Andonny Garcia are the other authors of the paper from Yale University. And Frank Fish from West Chester University.

The study was first published in Nature journal on Wednesday.

Study abstract:

The current proliferation of mobile robots spans ecological monitoring, warehouse management and extreme environment exploration, to an individual consumer’s home. This expanding frontier of applications requires robots to transit multiple environments, a substantial challenge that traditional robot design strategies have not effectively addressed. For example, biomimetic design—copying an animal’s morphology, propulsion mechanism and gait—constitutes one approach, but it loses the benefits of engineered materials and mechanisms that can be exploited to surpass animal performance. Other approaches add a unique propulsive mechanism for each environment to the same robot body, which can result in energy-inefficient designs. Overall, predominant robot design strategies favour immutable structures and behaviours, resulting in systems incapable of specializing across environments. Here, to achieve specialized multi-environment locomotion through terrestrial, aquatic and the in-between transition zones, we implemented ‘adaptive morphogenesis’, a design strategy in which adaptive robot morphology and behaviours are realized through unified structural and actuation systems. Taking inspiration from terrestrial and aquatic turtles, we built a robot that fuses traditional rigid components and soft materials to radically augment the shape of its limbs and shift its gaits for multi-environment locomotion. The interplay of gait, limb shape and the environmental medium revealed vital parameters that govern the robot’s cost of transport. The results attest that adaptive morphogenesis is a powerful method to enhance the efficiency of mobile robots encountering unstructured, changing environments.