Jul 28, 2016 | By Alec

Just a few years ago, robotic movement was rather limited in its options. But in part thanks to the advent of 3D printing, robots can now roll, crawl, run, fly or simply walk very well. This 3D printed ODOI robot can even mimic human gait and different moods while walking. But a team of Israeli researchers led by David Zarrouk have now ventured into another field of transportation: snake-like crawling, which enables robots to conquer numerous different terrains and even swim.

David Zarrouk (from the Ben Gurion University in Israel) is a well-known figure in the world of robotics, and no stranger to 3D printing either. Over the past few years he unveiled numerous innovative robotic designs, such as the six-legged 3D printed STAR robot that can change between different movement forms. But with his SAW robot (or Single-Actuator Wave robot), he is breaking open a whole new movement field. The SAW robot has been covered in a paper entitled Single actuator wave-like robot (SAW): design, modeling, and experiments, just published in the journal Bioinspiration & Biomimetics.

In the paper, Zarrouk describes his SAW as a new bio-inspired robot that relies on a continuously advancing wave. While you won’t find many creatures in nature that produce a continuously advancing wave, it is reminiscent of a snake’s muscle contractions that propel it forward. But the SAW is especially remarkable for being the first of its kind to use just a single motor to move around (both forwards and backwards), with a pair of wheels providing steering. As that single motor spins around, it causes the 3D printed spine-like frame to move in a waving motion – creating propulsion whenever the spines hit the ground. Specifically, this is a transverse wave that some tiny ocean organisms also use.

While still a work-in-progress robot, the remarkable SAW could thus be a far more efficient option than other robots because it only uses a single motor. While already more than capable of overcoming certain forms of terrain, Zarrouk’s robot could become a fantastic reconnaissance option in the near future. It could even be scaled down into a medical robot. As the researcher explained, this project can be traced all the way back to his undergraduate studies in 2004. “I realized back then that all you need is a single motor, but how you do it is a pretty difficult challenge,” he recalls in an interview. “During my PhD I developed a worm robot, but realized that wave locomotion could be excellent for self-propelled systems in the digestive system, and that a simple design with one motor will allow to shrink it enough to locomote inside the intestines.”

This concept grew further a few years ago when Zarrouk taught a mechanical design course. “I realized that the side projection of a spring in one direction is a circle and the other is a sine wave. Interestingly, If the spring rotates, the projection becomes an advancing wave. I figured out that this would be the simplest design I have ever thought of and started the design and building,” he says.

The result is remarkably simple design that could probably not be realized without 3D printing. The 3D printed plastic links are flexible in one dimension, like a bicycle chain. This lets them flex up and down, while remaining strong enough to propel the robot forward whenever they touch the ground. And they are quick. The largest version of the SAW has a top speed of 57 cm per second, while its design hardly suffers from sliding issues at all. But that high speed isn’t purely the result of wave movement. For the Israeli researchers discovered that they can boost movement speed by 13 percent by adding a set of spine-like constructions to each 3D printed link. These increase rotational speed whenever the link touches the ground. This effectively creates seven wavelengths of movement with just six wave cycles.

The current iteration of SAW is very simple to build, and is very lightweight and easy to scale both up and down. Zarrouk further said that it hardly requires any maintenance once operational. But of course this is still a 3D printed prototype, and there’s plenty of room for improvement. The steering system needs to be improved, while Zarrouk is also looking into ways that would allow the SAW to adapt to different types of terrain more effectively. For on uneven substrate, like gravel, the links don’t always touch a solid surface.

But even more ambitious is Zarrouk’s intention to make the SAW suitable for climbing through pipes and swimming in viscous liquids – the circumstances in which bacteria live. This could pave the way for a variety of medical applications, such as robots that can autonomously explore your intestines. It sounds uncomfortable, but then an intestinal biopsy is everything but comfortable already. Could this be the future of medical robots?

 

 

Posted in 3D Printing Application

 

 

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