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Bio-inspired robots: the jumping softies

2021-12-11T18:14:33.760Z


Modern robots are often powerful images of humans. In the end, however, researchers were more interested in remote-controlled fish, spiders and geckos. They are made from soft materials that mimic muscles and joints.


Enlarge image

Jumping robot made of soft material

Photo: Chongqing University / Shanghai University / CC BY 4.0

Robots can do amazing things now. Some have conversations, help around the house, or mow the lawn. The two-legged robot "Atlas" from the Boston Dynamics company resembles a human being so much in its movements that one could actually mistake it for humanoid in the twilight. The metal box even does a clean somersault from a standing start, and it also hops precisely like a squad athlete over an obstacle course. But Boston Dynamics has also built autonomous multi-legged bikes and taught them to walk like a puppy.

What most robots have in common is that they are made of solid metal parts, motors and plugs. But at first glance, the robot developed by a scientist working with Rui Chen from Chongqing University in China has nothing in common with a powerful machine. The device can jump without arms or legs and does not need powerful motors. It looks more like the scientists were inspired by nature and mimicked a flatfish. The round flatbread weighs just over a gram and is 6.5 centimeters long, reports Chen in the journal Nature Communications. It has a soft structure and is flexible like a pancake.

Such devices are called soft robots. In the past, technicians have relied on a wide variety of control and drive concepts when developing such parts. Some worked, for example, with springs, dielectric, elastomeric, magnetic, pneumatic, chemical actuators. This is the name of the control units that convert a signal into mechanical movements. The improvement of the jump height and width as well as the jump frequency was a great challenge. The researchers also wanted to control and navigate their devices as precisely as possible.

Chen's team relies on a so-called electrohydrostatic bending drive for their development.

The jumping movement is generated by lightning-fast, electrically driven liquid redistribution, only a few millimeters flat mini device.

The result is a movement similar to the contraction of a muscle - the soft robotic disc pushes itself off the ground and flies into the air.

The hopping flatfish

The construction, which is actually circular and filled with a special liquid, is constructed in such a way that an electric field is generated in the center, which pushes the liquid outwards. This creates a donut-shaped bag. Chen's team works with semicircular chambers, which they arrange in certain constellations. Controlled jumping is made possible by the redistribution of the liquid. The researchers write that this could help the robot to move even in rough terrain.

The robot was able to jump 7.68 times its own height.

In addition, he overcame a distance of six body lengths per second, which corresponds to around 39 centimeters.

To do this, the tiny thing, which is held together with a plastic film, hopped over obstacles such as cubes, wires, steps or gravel.

While earlier actuators with this functionality were only able to jump upwards and gravity then brought them back to the ground, the researchers working with Chen were able to generate a controlled forward movement.

When the researchers coupled two of their mini robots, they could control the direction of the jump quite well.

However, the development of the Chinese is still dependent on external energy and is fed by small lines.

But the device could transport small sensors and record temperature differences or ultraviolet light.

This allows robots of this type or similar to be used in the long term to monitor environmental changes.

The tiny and light devices could possibly cope better in rough terrain than large robots and could, for example, measure pollution levels in buildings or industrial plants.

Recently, researchers have moved further and further away from classic robot development.

The concepts of some bio-inspired machines no longer have much to do with human images.

While motors and bulky metal components and connectors used to dominate, some researchers are now working with soft materials that replace muscles or skin.

Scientists are inspired by all kinds of creatures: fish, jellyfish, reptiles or insects. A jellyfish, for example, glides through the sea in a unique, elegant way. Robot developers want to learn from this by constantly developing new and better actuators that perfect their movements. The Chinese robotics specialists may also have copied something from nature. After all, some crawling insects can also hop.

At the Max Planck Institute for Intelligent Systems in Stuttgart and Tübingen, scientists recently built a robotic spider that could jump over ten times its body size. The special feature of the device are the joints of the knee-joint robot, which are extremely flexible. The principle behind this is similar to that of the actuators that were used for the Chinese jumping pancake from China. The joint mimics a spider-inspired exoskeletal mechanism made up of both rigid and softer elements that, through the use of hydraulic forces, work in a similar way to the animal's leg extension.

Sometimes scientists also go the other way around. You are not looking directly for inspiration from nature for a technical application, but first and foremost you want to understand nature better with the help of robotics. The Max Planck researcher Ardian Jusufi succeeded in doing this. He discovered how essential the tail is for the landing behavior of jumping geckos - with the help of soft robots. "With them we were able to measure something that we couldn't measure in the animals in the rainforest," Jusufi told SPIEGEL.

The background: a certain species of animal, the fringed-tailed house gecko, which lives in the jungle of Singapore, survives the impact on surfaces unscathed, even though it jumps from tree to tree at around 21 kilometers per hour. He can balance the jump perfectly and does not fall off the branch. The small animal, which weighs a good two grams, apparently only succeeds in doing this because it has a tail. Sometimes, however, these animals shed their tails when danger is imminent. Such specimens have a disadvantage. They promptly fell from the tree, the researchers observed.

In recordings from high-speed cameras, the researchers discovered that the animals use their tail as an extended landing area for the trunk and stretch the trunk backwards by up to 100 degrees. This reduces the forces that occur on the animals' hind feet. To test their hypothesis, the researchers developed a physical model based on their observations and built a soft robot gecko, whose tail could be removed if necessary, in order to test both flight variants in the laboratory. In fact, their suspicions were confirmed. The longer the gecko tail, the less force was acting on the robot's hind feet. And the easier it was for the robo-gecko to hold on to the wall in the laboratory.

In a next step, Jusufi hopes that the elegant jumping technique could turn into an application for a new type of robot. For example, gecko drones could be developed that could land on uneven surfaces more safely than other aircraft. It is conceivable, for example, that it could be used in an earthquake area, where such devices search for destroyed regions and collect data from all possible sensors. "With gecko technology, such a robot could basically land anywhere - on telephone poles, on smooth walls or destroyed houses," says Jusufi.

But, emphasizes the Swiss, it is not always important in soft robotics to copy nature as well as possible.

First of all, you have to understand them.

But with a view to further development, soft robots offer several advantages over conventional machines.

You could interact with people more safely and better, move more smoothly.

Behind the processes of conventional machines such as Atlas, the somersaulting robot from Boston Dynamics, there is ultimately a very complex control technology.

In comparison, nature is more robust and much better able to deal with disruptions effectively.

Robots like Atlas are precise, fast and powerful.

"But nature is much more efficient, animals can use their bodies much more skillfully," says Jusufi.

Source: spiegel

All tech articles on 2021-12-11

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