Acrobotics: a revolutionary movement

One small backflip for a robot is a giant leap for robotics. A world populated by athletic automatons is just a hop, skip and jump away. Cathal O’Connell reports.

Boston Dynamics

Atlas is an unlikely looking gymnast. But looks aren’t everything. He springs lithely across the floor, hops on to a platform half his height, jumps to another, deftly turns 180 degrees and leaps backwards, flipping in mid-air before sticking a neat landing. He holds his arms aloft like a triumphant Olympian. Not bad for a robot.

The time of robots being defeated by obstacles as devilish as steps and stairs is coming to an end. Atlas heralds a new generation agile enough to manoeuvre over natural terrain. Soon nothing will be off limits. With about half the Earth’s land mass inaccessible to wheeled vehicles, these light-footed humanoids could be deployed for any number of missions, from fighting bushfires to search and rescue.

Early two-legged robots looked like refrigerators with legs, and were about as nimble. The robots were slow because they were designed to be ‘statically stable’– their weight always solidly supported on bent knees and flat feet.

In 2000, after more than a decade of experimentation, the Honda company came up with ASIMO (short for Advanced Step in Innovative MObility and of course a play on Isaac Asimov’s name). With the ability to shift its centre of gravity, ASIMO walked with something almost but not quite like a human gait, with a maximum speed of 1.6 km/h (adult humans walk at about 5 km/h).

The smaller and cuter Nao, released in 2008 by SoftBank Robotics in Japan and now used by universities around the world for robotics research and education, uses a similar design with a comparably slow shuffling walk.

We are used to such underwhelming robot motion. Which is what makes the improving agility of Atlas, first unveiled to the world in 2013, so striking.

Atlas is the poster bot for US-based Boston Dynamics, founded two decades ago as a spin-out from research by legged robot pioneer Marc Raibert at MIT. Raibert started out in the 1980s with the goal of making robots that could not only walk but run. To study the dynamics of balance and motion in its simplest form, he built robots that moved on just one leg, hopping about like autonomous pogo sticks.

Atlas is descended from these simple hoppers, with a ‘dynamically stable’ gait. It uses its own momentum to carry it through each step – much more like a natural human walk.

This movement style makes Atlas amazingly versatile, able to boldly stroll where no bot has gone before, such as over rough terrain. Atlas is more rugged in its decision making too, emphasising speed over precision. Traversing through a snowy landscape, Atlas will stumble a little, and might even fall over now and then. But don’t we all?

Much of Boston Dynamics’ research, including the development of Atlas, has been funded by the US Defense Advanced Research Projects Agency (DARPA). In 2017 the company was bought by SoftBank, which is more interested in developing robots for aged care than military use.

Where backflipping fits into domestic help, though, we can only begin to guess.

PERCEPTION: Just like autonomous cars, Atlas uses LiDAR (light detection and ranging) to map out its environment in three dimensions by scanning a laser around and analysing how it reflects back. To figure out where a specific object is in space, its stereo vision system works a bit like the depth perception in human vision.

BALANCE: To orient itself in space, Atlas uses the gizmos now standard in drones and other self-righting vehicles: gyroscope sensors and accelerometers. What really gives Atlas an eerily human quality is something Raibert calls ‘whole-body movement’. This refers to how Atlas coordinates the motions of its arms, torso and legs to retain balance.

MOTORS: Atlas’s ‘muscles’ are more than two dozen hydraulic actuators, driven by a battery-powered electric pump. The hydraulics are somewhat pliant, to absorb shocks and help plant that stable landing. Right now its batteries only last about an hour, a barrier to any practical real-world application.

BODY: The latest version of Atlas is sleeker than the hulking framed version that competed in the 2015 DARPA Robot Challenge. The Boston Dynamics team used 3D printing to create the legs, so the actuators and hydraulic lines are embedded inside the structure, rather than being pumped through separate lines. An elegant solution, and one that looks less messy too.

AUTONOMY: If knocked down, Atlas can pick itself up. It can identify, walk over and pick an object up. It can stack shelves; it can open a door and walk though. But it still needs a human with a remote control to tell it where to go and what to do. Humans are very much still in charge.

Anthony Calvert

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Cathal O'Connell is a science writer based in Melbourne.
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