Throwable Robot Ball Unfolds Legs to Walk

QRoSS can bounce around and then extend four legs to walk over rough terrain

2 min read

Evan Ackerman is IEEE Spectrum’s robotics editor.

Throwable Robot Ball Unfolds Legs to Walk

Anyone who has much in the way of experience with robots is painfully aware of their fragility. Robots like Flyability’s Gimball deal with this through the creative use of roll cages, which have a useful side effect of allowing the robot to dynamically navigate through direct surface contact. Roll cages can protect ground robots too, although it’s a bit more problematic because using a full roll cage makes it difficult for the robot to do anything but roll. At IROS, Japanese researchers presented a design for a robot that can be tossed, roll along the ground, and then pop out four legs when it needs to scramble around.

The researchers cite three inspirations for their design. We’re already familiar with the first one, MorpHex:

And then there’s this little guy called Haro, from Gundam:


Lastly, from Star Wars, the Droidekas (which is what I thought of when I first saw QRoSS):

As far as real robots go, the primary difference between QRoSS and MorpHex is that QRoSS uses a walking system that’s completely independent from the outer shell. The big advantage of this is that the shell acts as a passive shock absorber, allowing the robot to the rolled (or, hypothetically, thrown) without damaging it. In a disaster area, for example, a human could chuck the robot like a baseball into a dangerous area from a safe one, and after bouncing a few times, QRoSS simply sprouts legs and starts walking around. Legs are excellent at dealing with very rough terrain, and the design of QRoSS allows you to use legs when necessary without having to always worry about how fragile they are, since any slip and fall just turns into a bouncy roll.

The other advantage of a more or less spherical robot is that it can use rolling as a faster and more efficient method of locomotion, as long as the terrain is favorable. QRoSS has a walking speed that tops out at about 0.1 m/s, while its rolling speed is nearly 0.6 m/s.

QRoSS II (the current version) weighs almost 2.5 kilograms, with a 30-centimeter diameter shell, so it’s not yet optimized for throwing. Researchers are still studying its mobility techniques and characteristics, so they haven’t really been focusing on size, weight, or cost. However, the design seems like it should be scalable, and there’s no reason to think that there’d be a very high manufacturing cost: there are twelve servos (three per leg), some electronics, and legs made of a combination of titanium and shape-memory alloy with polyurethane foam shock absorbers. We’re hoping that future iterations might be smaller (on the order of palm sized), and affordable enough to be disposably tossed wherever they might be needed.

“Development of Quadruped Walking Robot With Spherical ShellMechanical Design for Rotational Locomotion,” by Takeshi Aoki, Satoshi Ito, and Yosuke Sei from the Chiba Institute of Technology in Japan, was presented this month at IROS 2015 in Hamburg, Germany.

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