Aug 15, 2017 | By Benedict

Researchers at the University of Arizona have 3D printed a modular robot that mimics the movement of a sea turtle and uses reinforcement learning to figure out its best strategy for movement. The researchers say the 3D printed “C-Turtle” robot could be deployed on Mars.

Dry, dusty, and cold: Mars hardly seems like the ideal home for water-loving sea turtles. Found in oceans across the world, some species of the adorable reptiles can grow up to three meters in length, but you’ll never, ever find them hanging out in a desert.

It’s therefore pretty strange that a group of researchers believes sea turtles could hold the key to robotic transport on Mars.

But believe it they do: using 3D printed parts, cardboard, and a Raspberry Pi, a team at the University of Arizona has created a modular robot that mimics the movement of the sea turtle. Instead of swimming through water, however, the “C-Turtle” robot shuffles its way across dry and dusty terrain.

“The goal of the C-Turtle project is to develop cheap robots made from paper and let each robot adapt its (crawling) motion by the use of reinforcement learning,” the researchers explain. “By using laser cutting and lamination as manufacturing methods, a fully functioning robot can be deployed in under a day with an optimal movement strategy for each robot and environment.”

Perhaps the most interest part of the partially 3D printed C-Turtle is its ability to discover new locomotion strategies. Rather than follow a pre-programmed movement pattern, the robot is able to experiment with different movement strategies in order to identify what works best on its current terrain.

(Images: Interactive Robotics Lab/ASU)

This could be massively useful in places where researchers aren’t familiar with the terrain: a foreign planet, for example.

“A locomotion strategy for the C-Turtle was learned with a reinforcement learning method both in the lab and in a desert environment,” the researchers say. “The used method, Group Factor Policy Search, requires only few executions to uncover an optimized movement strategy.”

Impressively, the 3D printed robot is able to figure out an appropriate movement strategy in just one hour, meaning it could get straight to work in an environment like Mars.

Although the C-Turtle’s movement strategy varies depending on the terrain, the robot basically moves using a pair of laterally mounted “fins,” which are made from either cardboard or a 3D printed material (for rougher ground) and which move with two degrees of freedom. The underside of the robot is flat, with a slightly upturned nose, allowing the robot to essentially “swim” along a dry, solid surface.

A closer look at the C-Turtle reveals few obvious parallels with its reptile namesake, but the robot is nonetheless a fascinating piece of engineering.

The C-Turtle is constructed as a single laminate device comprised of five layers, with the upper and lower surfaces made of cardboard and fixed with an adhesive backing. A laser cutter is used to make hinge designs and mounting holes, before the cut layers are stacked together over a central un-cut layer of thin plastic sheeting that acts as a hinge. The entire device is then cut from the laminate and bonded using a t-shirt press.

After lamination and bonding, the body is folded into shape and assembled with servo motors, 3D printed servo horns, and fins, which are held in place by removable plastic rivets. Batteries and the onboard Raspberry Pi are then mounted on the body using electrical tape and rivets.

The researchers behind the project have taken every step to ensure that building a C-Robot is fast and efficient. For example, 3D printing the servo horns take around an hour, as does the total assembly of other components. This means the two processes can be carried out simultaneously to make the total production time just one hour in total.

(Images: Interactive Robotics Lab and IDEAlab/ASU)

The University of Arizona team carried out learning experiments on the C-Turtle in a labs and in the desert near Phoenix, Arizona. In the lab, five independent learning sessions were conducted for four different fin designs. By going through 10 “policy search iterations” for each session, the testing resulted in a total of 1,050 policy executions per fin over a period of 2-3 hours.

This process was repeated in the desert environment, using natural terrain instead of sand-mimicking poppy seeds.

Although the C-Turtle robot might need further modifications before it is seriously considered for deployment on another planet, the robot provides a fascinating glimpse at how modern manufacturing techniques like additive manufacturing can be combined with clever algorithms to produce a cheap (the robot costs just $70) and functional robotic system.

A research paper about C-Turtle, written by Kevin Sebastian Luck, Joseph Campbell, Michael Andrew Jansen, Daniel M. Aukes, and Heni Ben Amor, can be found here. The paper was presented at the Robotics: Science and Systems Conference at MIT in July.

The cut files for the C-Turtle can be found here.



Posted in 3D Printing Application



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Jason wrote at 8/16/2017 6:36:28 AM:

Sooo we are going to spend millions of dollars on a rocket and fuel to send the cheapest possible robots to mars with paddles for feet that will wear out quickly due to all the scuffing and scraping they will do to move?! If it can barely move on perfectly flat ground how is it going to handle anything else"

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