A new study features the first in-depth look at the jumping prowess of the globular springtail (Dicyrtomina minuta).

This diminutive hexapod backflips into the air, spinning to over 60 times its body height in the blink of an eye.

Globular springtails are tiny, usually only a couple millimeters in body length. They don’t fly, bite, or sting. But they can jump. In fact, jumping is their go-to (and only) plan for avoiding predators. And they excel at it—to the naked eye it seems as though they vanish entirely when they take off.

“No other animal on earth does a backflip faster than a globular springtail.”

“When globular springtails jump, they don’t just leap up and down, they flip through the air—it’s the closest you can get to a Sonic the Hedgehog jump in real life,” says corresponding author Adrian Smith, research assistant professor of biology at North Carolina State University and head of the evolutionary biology and behavior research lab at the North Carolina Museum of Natural Sciences. “So naturally I wanted to see how they do it.”

Finding the globular springtails was easy enough—they’re all around us. The ones in this study are usually out from December through March. Smith “recruited” his research subjects by sifting through leaf litter from his own backyard. But the next part proved to be the most challenging.

“Globular springtails jump so fast that you can’t see it in real time,” Smith says. “If you try to film the jump with a regular camera, the springtail will appear in one frame, then vanish. When you look at the picture closely, you can see faint vapor trail curlicues left behind where it flipped through the one frame.”

Smith solved that problem by using cameras that shoot 40,000 frames per second. He urged the springtails to jump by shining a light on them or lightly prodding them with an artist’s paintbrush. Then he looked at how they took off, how fast and far they went, and how they landed.

Globular springtails don’t use their legs to jump. Instead, they have an appendage called a furca that folds up underneath their abdomen and has a tiny, forked structure at its tip. When the springtails jump, the furca flips down and the forked tip pushes against the ground, launching them into a series of insanely fast backflips.

What do we mean by insanely fast?

“It only takes a globular springtail one thousandth of a second to backflip off the ground and they can reach a peak rate of 368 rotations per second,” Smith says. “They accelerate their bodies into a jump at about the same rate as a flea, but on top of that they spin. No other animal on earth does a backflip faster than a globular springtail.”

The springtails were also able to launch themselves over 60 millimeters into the air—more than 60 times their own height. And in most cases, they went backward.

“They can lean into a jump and go slightly sideways, but when launching from a flat surface, they mostly travel up and backward, never forward,” says Jacob Harrison, a postdoctoral researcher at the Georgia Institute of Technology and paper coauthor.

“Their inability to jump forward was an indication to us that jumping is primarily a means to escape danger, rather than a form of general locomotion.”

Landing was found in two styles: uncontrolled and anchored. Globular springtails do have a sticky forked tube they can evert—or push out of their bodies—to grapple a surface or halt their momentum, but Smith observed that bouncing and tumbling to a stop was just as common as anchored landings.

“This is the first time anyone has done a complete description of the globular springtail’s jumping performance measures, and what they do is almost impossibly spectacular,” Smith says. “This is a great example of how we can find incredible, and largely undescribed, organisms living all around us.”

The work appears in Integrative Organismal Biology.

Source: North Carolina State University

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A relatively low-cost, easy-and-fast-to-assemble quadruped robot called “Solo 8” can be upgraded and modified, researchers report.

Solo 8 could open the door to sophisticated research and development to teams on limited budgets, including those at startups, smaller labs, or teaching institutions.

Robots capable of the sophisticated motions that define advanced physical actions like walking, jumping, and navigating terrain can cost $50,000 or more, making real-world experimentation prohibitively expensive for many.

The researchers designed the device with an eye to making robot research and pedagogy more accessible to a broader range of institutions and labs and—through the use of the same open-source platform—allow researchers to compile comparative data—a critical step towards rapid progress in robotics.

“Our robot platform is a great base to quickly prototype and build high-performance hardware…”

Solo 8’s functionality, including torque-controlled motors and actuated joints, allows it to behave like far more expensive robots: it can, for example, perform jumping actions, walk in multiple configurations and directions, and recover orientation, posture, and stability after being overturned.

Additionally, all the components of Solo 8 can be either 3D-printed or bought in a shop, and the construction files are freely available online, enabling other scientists to leverage the modular set-up when prototyping and developing their own technology.

The robot makes possible research in such areas as:

• Exploration of animal-based limb movement and movement over laboratory surfaces, gravel, soil, sand, mud, and other such terrains.
• Reinforcement learning for complex and dynamic behaviors, including those that push performance to stress limits that would be too risky to attempt with expensive platforms.
• Very dynamic locomotion (including parkour-style behaviors), which very few robots can perform
• Manipulation of the environment (such as opening doors or pushing buttons).
• Integration of robots with advanced communications technology.

“Already many universities have approached us, and wish to make a copy of our robot and use it as a research platform,” says Ludovic Righetti, associate professor of electrical and computer engineering and mechanical and aerospace engineering at New York University’s Tandon School of Engineering, a research group leader at the Max Planck Institute for Intelligent Systems (MPI-IS) in Tübingen and Stuttgart, Germany in addition to his duties at Tandon. He explains that the concept was recently used by the department of empirical inference at the MPI-IS to build robotic fingers that can manipulate objects.

“Our robot platform is a great base to quickly prototype and build high-performance hardware,” he says.

“For a research group to develop such a robot themselves, it takes easily four years of work.”

“In return we benefit, because other researchers can contribute to the project; for example colleagues at the LAAS-CNRS in France have developed an electronic board to help communicate with the robot over WiFi. Also, complex control and learning algorithms can be rapidly tested on the platform, decreasing the time from idea to experimental validation. It greatly simplifies our research, and our open-source approach allows us to compare algorithms with other laboratories,” Righetti says.

“In my lab here in New York, we have developed very efficient motion optimization algorithms, but testing them on a complex, heavy robot can easily take half a year of work for several researchers, while this can be done more easily with Solo. That was a big deal for us.”

“For a research group to develop such a robot themselves, it takes easily four years of work,” says Alexander Badri-Spröwitz, leader of the Dynamic Locomotion research group at MPI-IS. “Additionally, you need a wide range of expertise. Our platform is the combined knowledge of several teams. Now any lab worldwide can go online, download the files and print the parts, and buy the remaining components from the catalog. And everybody can add extra features, within a few extra weeks. Done—you’ve got yourself a world-class robot.”

He adds that with an estimated price of a few thousand Euros, the robot, homemade and easy to tweak to meet individual research goals, is more accessible to greater numbers of researchers and instructors than a store-bought legged robot.

“Solo has some novel capabilities that we are interested to explore in the future,” says Felix Grimminger, a mechatronics engineer. “It has an extensive range of motion, for example. When the robot falls on its back, it can configure the legs the other way and just stand up. Or it can jump up to reach 65 centimeters [25.59 inches] from a standing height of 24 cm [9.44 inches].”

Thanks to torque-controlled motors, the robot achieves a spring-like behavior, which perform like muscles and elastic tendons in animal legs.

“Note that the robot uses virtual springs, not mechanical springs. And as virtual springs, they can be programmed. You can, for instance, adjust the spring stiffness from soft to hard, which is interesting because we see variable stiffness in humans and animals, and with adjusted stiffness the robot achieves adaptive and robust locomotion behavior,” Badri-Spröwitz adds.

Solo 8 weighs just over 2 kilograms (4.4 lbs), providing a very high power to weight ratio. Most quadruped robots are significantly heavier and therefore more dangerous and harder to handle in a research environment. With a low weight, it now becomes easier and safer for students to handle the robot, which can even be carried in a backpack to be transported home or to a conference.

The robot carries the number eight in its name as an indicator of its eight actuated joints: each robotic leg can change its angle and length. Researchers recently finished a new version, however, and they’ve conducted the first tests with 12 degrees of freedom, three per leg. The new robot can now also step sideways.

“Because of the additional degrees of freedom it will be a lot more versatile and will be able display more interesting and complex behaviors,” says Badri- Spröwitz.

The researchers’ work has been accepted for publication in Robotics and Automation Letters. The researchers will present the work virtually later this month at ICRA, the International Conference on Robotics and Automation.

Funding for the research came from Righetti’s ERC Starting Grant and then by several MPI-IS’ grassroots projects and a US National Science Foundation grant.

Source: New York University

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Wiggly ‘Mini Rover’ can handle otherworldly sand traps

A new robot called the “Mini Rover” has complex locomotion techniques robust enough to help it climb hills covered with granular material, report researchers.

It may also avoid the risk of getting stuck on some remote planet or moon.

The rolling hills of Mars or the moon are a long way from the nearest tow truck. That’s why the next generation of exploration rovers will need to be good at climbing hills covered with loose material and avoiding entrapment on soft granular surfaces.

Built with wheeled appendages that can be lifted and wheels able to wiggle, the new Mini Rover could be the right robot for the job.

“This rover has enough degrees of freedom that it can get out of jams pretty effectively.”

Using a complex move the researchers dubbed “rear rotator pedaling,” it can climb a slope by using its unique design to combine paddling, walking, and wheel spinning motions. Researchers modeled the rover’s behaviors were modeled using a branch of physics known as terradynamics.

“When loose materials flow, that can create problems for robots moving across it,” says Dan Goldman, a professor in the School of Physics at the Georgia Institute of Technology.

“This rover has enough degrees of freedom that it can get out of jams pretty effectively. By avalanching materials from the front wheels, it creates a localized fluid hill for the back wheels that is not as steep as the real slope. The rover is always self-generating and self-organizing a good hill for itself.”

A robot built by NASA’s Johnson Space Center pioneered the ability to spin its wheels, sweep the surface with those wheels, and lift each of its wheeled appendages where necessary, creating a broad range of potential motions. Using in-house 3D printers, the researchers collaborated with the Johnson Space Center to recreate those capabilities in a scaled-down vehicle with four wheeled appendages that 12 different motors drive.

“The rover was developed with a modular mechatronic architecture, commercially available components, and a minimal number of parts,” says Siddharth Shrivastava, an undergraduate student in Georgia Tech’s George W. Woodruff School of Mechanical Engineering.

“This enabled our team to use our robot as a robust laboratory tool and focus our efforts on exploring creative and interesting experiments without worrying about damaging the rover, service downtime, or hitting performance limitations.”

The rover’s broad range of movements gave the research team an opportunity to test and study many variations using granular drag force measurements and modified Resistive Force Theory.

Shrivastava and School of Physics PhD candidate Andras Karsai began with the gaits the NASA RP15 robot explored, and then were able to experiment with locomotion schemes that could not have been tested on a full-size rover.

The researchers also tested their experimental gaits on slopes designed to simulate planetary and lunar hills using a fluidized bed system known as SCATTER (Systematic Creation of Arbitrary Terrain and Testing of Exploratory Robots) that could be tilted to evaluate the role of controlling the granular substrate.

“By creating a small robot with capabilities similar to the RP15 rover, we could test the principles of locomoting with various gaits in a controlled laboratory environment,” Karsai says. “In our tests, we primarily varied the gait, the locomotion medium, and the slope the robot had to climb. We quickly iterated over many gait strategies and terrain conditions to examine the phenomena that emerged.”

In the paper, the authors describe a gait that allowed the rover to climb a steep slope with the front wheels stirring up the granular material—poppy seeds for the lab testing—and pushing them back toward the rear wheels. The rear wheels wiggled from side-to-side, lifting and spinning to create a motion that resembles paddling in water. The material pushed to the back wheels effectively changed the slope the rear wheels had to climb, allowing the rover to make steady progress up a hill that might have stopped a simple wheeled robot.

“This combination of lifting and wheeling and paddling, if used properly, provides the ability to maintain some forward progress even if it is slow.”

The experiments provided a variation on earlier robophysics work in Goldman’s group that involved moving with legs or flippers, which had emphasized disturbing the granular surfaces as little as possible to avoid getting the robot stuck.

“In our previous studies of pure legged robots, modeled on animals, we had kind of figured out that the secret was to not make a mess,” says Goldman. “If you end up making too much of a mess with most robots, you end up just paddling and digging into the granular material. If you want fast locomotion, we found that you should try to keep the material as solid as possible by tweaking the parameters of motion.”

But simple motions had proved problematic for Mars rovers, which got stuck in granular materials. Goldman says the gait discovered by Shrivastava, Karsai, and Ozkan-Aydin might be able to help future rovers avoid that fate.

“This combination of lifting and wheeling and paddling, if used properly, provides the ability to maintain some forward progress even if it is slow,” Goldman says. “Through our laboratory experiments, we have shown principles that could lead to improved robustness in planetary exploration—and even in challenging surfaces on our own planet.”

The researchers hope next to scale up the unusual gaits to larger robots, and to explore the idea of studying robots and their localized environments together.

“We’d like to think about the locomotor and its environment as a single entity,” Goldman says. “There are certainly some interesting granular and soft matter physics issues to explore.”

Though the Mini Rover was designed to study lunar and planetary exploration, the lessons learned could also be applicable to terrestrial locomotion—an area of interest to the Army Research Laboratory, one of the project’s sponsors.

“This basic research is revealing exciting new approaches for locomotion in complex terrain,” says Samuel Stanton, program manager at the Army Research Office, an element of the US Army Combat Capabilities Development Command’s Army Research Laboratory.

“This could lead to platforms capable of intelligently transitioning between wheeled and legged modes of movement to maintain high operational tempo,” he says.

The research appears in Science Robotics. The work was supported by the NASA National Robotics Initiative and the Army Research Office. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the sponsoring agencies.

Source: Georgia Tech

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