IEEE Spectrum October, 2012 - 38

Arm & ActuAtors

productivity. Brooks isn't worried. He acknowledges that, in the
beginning, Baxter will perform only a limited number of tasks.
But as Rethink continues to upgrade the robot-especially its
software-Baxter's full potential will become evident. And then,
Brooks predicts, his new robot will "sell like hotcakes."
fter introducing us to Baxter, Brooks has us follow
him through the maze of beige cubicles, test stands, and
scattered piles of robot parts that make up Rethink's
Boston headquarters, which is unusually quiet today. "We had
a company outing yesterday," the 57-year-old Brooks says by
way of explanation, a faint accent revealing his Australian origins. "Maybe some folks are still goofing around."
Once we get to his office, Brooks relaxes on a couch. Dressed
in a button-down shirt, jeans, and red-and-blue argyle socks,
he's surrounded by relics of his robotics past. One framed picture shows Genghis, a six-legged robot he built at MIT in the
late 1980s, which could crawl and climb over obstacles with a
remarkable, insect-like gait. Contrary to the conventional wisdom of the time, Genghis required very little programming
to produce its complex behavior. It was just one of many bold,
counter intuitive results that surprised the community and
helped establish Brooks's reputation as "the bad boy of robotics."
In addition to his notable academic career, Brooks and
two of his students, Colin Angle and Helen Greiner, founded
iRobot in 1990. The start-up broke ground in two distinct areas:
its Roomba vacuum cleaning robot, which became a runaway
hit in the consumer market, and its PackBot military robot,
used in Iraq and Afghanistan to scout for improvised explosive
devices. With these accomplishments under his belt, Brooks
could have retired comfortably. Instead, he decided to phase
out his involvement with iRobot, gave up his tenured position at MIT, and founded Heartland Robotics, which recently
rethought its name and became Rethink.
Brooks's vision for Rethink can be traced back to the time he
spent in China supervising the manufacture of iRobot products.
"I realized that [outsourcing manufacturing to China] wasn't sustainable, because once the cost of Chinese labor starts to go up,
the appeal of doing a product there starts to go away," he says. He
concluded that a fairly simple robot could do lots of those tasks,
like basic material handling, packing and unpacking boxes, and
polishing and grinding. Brooks's second realization was that the
same advances in processors and sensors that were making PCs
and smartphones better and cheaper would benefit robots, too.
From the beginning, says David "DMX" Lewis, Rethink's
senior mechanical engineer and one of its earliest employees,
"the vision was a two-armed robot and a head, because Rod had
envisioned something that can go in and sit next to a person on
the assembly line and help them out." But they decided to start
with a simple design and build up from there. At first, the robot
was just a single joint powered by two gearboxes salvaged from
power drills. Then it grew into an arm with four degrees of freedom, a configuration known as SCARA, for selective compliant
assembly robot arm. Next came an arm with six degrees of freedom, similar to a popular robot arm of the 1980s called PUMA

Each arm has seven degrees
of freedom and can lift
2.25 kilograms (5 pounds) and
perform tasks at a roughly
human cadence with an accuracy
of about 0.5 to 1 centimeter.
The arms are powered by series
elastic actuators.

NA * iEEE SpEctrum * octobEr 2012

How
baxteR WoRks
Baxter may not be superfast,
superstrong, or superprecise like other
industrial robots, but it's smarter. It uses
vision to locate and grasp objects, and
you can program the robot to perform a
new task simply by holding its arms and
moving them to the desired position.
Baxter will even nod its head to let you
know it has understood you.

(programmable universal machine for assembly). After much
internal debate, Rethink's engineers decided that it needed a seventh degree of freedom, to better approximate the range of motion
of a human arm. A team of 30 mechanical and control engineers
completed the first two-armed prototype late last year and a
second-generation design early this year.
As the complexity of the robot has increased, keeping the
cost down has been a constant struggle. The engineers found
creative ways to work with less expensive components, which
often meant designing parts out of cheaper materials. (At one
point they attempted to build the entire arm, including the gear
systems, out of plastic, but that didn't pan out.) And by working
closely with local manufacturers, they were able to get the parts
they needed more cheaply and without compromising quality.
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Table of Contents for the Digital Edition of IEEE Spectrum October, 2012