SAW crawls, scrambles and swims with just one engine.

    If movement is needed, the device can resort to wheels and tracks, walk or go to the exotic level of crawling and swimming. Ways to get the robot to move described a lot. Sometimes it may even seem that nothing new can be invented. But this is far from the case. In a recently published paper, David Zarruk of Ben-Gurion University in the Negev describes a wave-like robot worm that is driven by just one actuator.

    The robot is called: single actuator wave-like robot or SAW. Its wavelike structure pushes it forward or backward. For turns need wheels taxiing. Such a design not only moves well over land, but can also climb in narrow crevices and float in water.

    Researchers say the crawling principles are borrowed from snakes. Although the progress of the SAW robot can be compared with the methods of movement of the worm, the analogy is conventional. The body of the earthworm is lengthened in one part due to thinning. The front end moves forward, the rear end rides behind it, which shrinks. The process is repeated. SAW is a sinusoid on the surface. The principles of the robot's movement are similar to the fact that some small marine animals use on a much smaller scale: microscopic organisms swim with the help of a flagellum.


    Video demonstration of the robot.

    Minimalism, ease of movement and high performance - this is what Zarruk has been working on for a long time. In an interview with IEEE Spectrum magazine, Zarruk said that back in 2004, as a student, he tried to recreate a wave motion similar to what exists in living organisms. While working on the doctoral thesis, Zarruk came up with the idea of ​​using wave motion for systems inside the digestive system. A simple system with a single motor can be reduced and used for movement within the intestine.

    A couple of years ago, Zarruk taught a course on product design and talked about springs. Then he noticed that in one projection the spring is a circle, in the other - a sinusoid. If the spring rotates, the wave simply moves. The simplicity of the principles of the movement interested the researcher. Upper picture: the motor rotates the spiral relative to the body. Bottom picture: 25 links gird a spiral, they are attached to the body and do not rotate. In SAW one engine. It rotates the spine of the robot - a rigid spiral. The latter is surrounded by a series of links printed on a 3D printer. These links are movable in the same plane, like parts of a bicycle chain. The spiral rotates, and the links go up and down. In this case, the links move in such a way that, when in contact with the surface, the robot is pushed forward.







    The wave goes from right to left, and the links in contact with the ground move slightly to the left and rotate clockwise.

    The SAW robot can only move forward or backward. For reversing it is enough to twist the spiral in the opposite direction. He is helped by two wheels on the body, which are otherwise passive: they do not power the device. It may seem that the only way to accelerate the movement is to rotate the spiral faster. But the researchers added teeth to the links, which allow making the movements of seven waves in six cycles. So the rate increased by 13%. Special teeth do not prevent the links from moving relative to each other.




    It was made several models of different sizes. The largest (multicolored) develops a speed of 5.6 waves per second or 57 centimeters per second. She can climb up between two narrowly set surfaces at a speed of 8 cm / s. The model enclosed in a waterproof case floats at a speed of 6 cm / s. SAW works not only on the flat floor of the laboratory, it overcomes the folds of the ground and passes stones and grass. SAW is not just a toy. Now he was able to reduce to the size of the handle (the lowest sample in the photo above). In the future, the robot can be miniaturized to such an extent that it will be able to remove the human intestines and take samples for biopsy. Work on a further decrease is already underway.





    According to Zarruk, the robot requires almost no maintenance, which is unusual for a dynamic structure produced by 3D printing. In the future, the taxi system will change - the current is not too elegant. Researchers want to try joining two SAW robots through a hinge. And if it happens on the fly to change the frequency of the waves and their amplitude, the robot can better adapt to different surfaces, wriggle through pipes of many diameters and optimize the movement for each of the fluids.

    Single actuator wave-like robot (SAW): design, modeling, experiments

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