Cockroach Robot Grows Tail, Does Flips

UC Berkeley VelociRoach robot with tail
Image: UC Berkeley

The nice thing about making bio-inspired robots is that you can take inspiration from biology, but you don’t have to be constrained by it. Lots of different animals have lots of different adaptations that make them good at lots of different things, but (sadly) there isn’t really one SuperAnimal that incorporates all of these adaptations at once. With robots, we can make this happen.

UC Berkeley’s Biomimetic Millisystems Lab, headed by Ron Fearing, has years of experience building all kinds of different flavors of robotic roaches, many of which have been modeled fairly closely on actual roaches. However, their latest roachbot (presented at IROS 2017) makes a notable departure from the original insect: It’s got a tail, which actual cockroaches don’t, meaning that it can flip itself over with ease.

Little legged robots like this one have used actuated tails for all kinds of things, most notably mid-air stabilization and assisting in rapid direction changes while running. This particular robot is a 77.5-gram, 18-centimeter-long VelociRoACH that has been outfitted with a protective polycarbonate shell for impact protection along with a minimal actuated tail to flip it over if it falls onto its back.

Most tails on dynamic robots are heavy, awkward things with weights on the end, since their functionality depends on having enough inertia to affect the body of the robot when they’re swing around. This tail, on the other hand, is minimal—it’s basically a rigid carbon fiber stick that rotates, pushing against the ground to allow the robot to roll itself over:

The tail and shell combine to create a little legged robot that’s super resilient. It can happily bounce down a flight of stairs and land on the floor, autonomously right itself in the blink of an eye (actually about a quarter of a second), and skitter off again. The righting technique is very reliable, too, as testing showed the robot to be able to flip over in a single try on wood, tile, and carpet. Rocks (both fixed and loose) were a bit tricker, with success rates dropping to 80 percent, but since the robot can just try again with minimal expenditure of time and energy, 80 percent is easily reliable enough. 

Since tails are good for so many other things, the next step for this particular roachbot will be to see what else it can do, the researchers say:

The potential of using a single degree of freedom low-mass tail for functions in addition to self-righting will be explored through control of the tail as an additional locomotion limb, further expanding the robot’s mobility. Since the tail can apply large forces relative to the legs with a long moment arm, impulsive tail motions could produce significant vertical jumps to clear obstacles or produce rapid turns.

Oh, and one last thing: In case you were wondering how real cockroaches manage to flip themselves over, it’s apparently more of an issue than you might think, according to The New York Times:

In a domestic situation, a roach may find itself on a smooth floor of polished wood, tile or stone. With a relatively high center of gravity and a smooth, rounded back, a roach that gets turned over for any reason will find it very hard to right itself without twigs, leaves or other uneven features for its legs to push against.

Hear that, cockroaches? You’d better get to work on a tail.

“Dynamic Terrestrial Self-Righting with a Minimal Tail,” by Carlos S. Casarez and Ronald S. Fearing from the University of California, Berkeley, was presented this week at IROS 2017 in Vancouver, Canada.

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