Monday, September 6, 1999
Science Watch
Researchers Building Robotic Prototypes, Lego Block by Lego
Block
By Lee Dye
Computer scientists at Brandeis University say they have taken a
significant step toward creating robots that will evolve into
ever more sophisticated machines, capable of repairing and
modifying their own hardware.
What they have come up with isn't exactly the "2001" film star,
Hal, or even R2D2 of "Star Wars." But they have produced
software that allows a computer to design structures, such as
bridges and cranes, without human intervention.
"It's a kind of science fiction," conceded Jordan Pollack,
associate professor of computer science at the university's
Volen National Center for Complex Systems in Waltham, Mass. "But
it works."
They pulled off their achievement with the help of toys designed
for children, the ubiquitous Lego blocks that have spread from
the kid's room to prestigious research laboratories around the
world. The small plastic blocks, manufactured by international
toy giant Lego Group, can be attached to each other in a variety
of ways, making it possible to build robotic prototypes in
minutes and with minimal cost.
Lego blocks were chosen because they lend themselves to modular
construction techniques, according to graduate researcher Pablo
Funes, who has done most of the work on the project.
"Legos are modular in the sense that they can be combined in
different positions," Funes said. "Any brick can attach to any
other brick."
The Brandeis scientists created algorithms, or computer
programs, that established the basic physics needed to build
strong structures. Then the computer was given a single Lego
brick, along with a goal, called a "fitness function"--in this
case to design a bridge two meters in length.
That single brick "mutated" into other bricks, and the computer
tried many ways to assemble the bricks into a bridge. Each step
along the way, it compared the structure with the physics model
contained in the software.
"That program basically calculates whether or not the structure
will collapse," Pollack said.
A day and a half later, the computer produced a cantilevered
design for a bridge.
The scientists then broke out their set of Legos and built a
real bridge exactly like the computer had designed.
It not only worked, Pollack said, but it was a good design. In
fact, it took humans centuries to develop similar
structures--bridges that are based on counterbalances.
The computer also designed a crane, based on an inverted
triangle, and a table.
The computer came up with the designs through a trial-and-error
process, adding one Lego at a time and checking against the
physics model to see if that strengthened or weakened the
structure. It had an amazing number of chances to get it wrong.
Two plastic bricks with eight studs--by which the bricks are
connected--can be put together 24 ways, according to Lego Group.
Three bricks can be assembled 1,060 ways. And just six bricks
can be put together in 102,981,500 different ways. The computer
used more than 200 bricks to design its bridge, so the
possibilities are virtually infinite.
The scientists say they gave the computer no commands other than
to start the task. But they are walking a fine line. Did the
computer succeed because they told it too much about what it was
supposed to do, or did it succeed because it was able to "think"
through the challenge, aided by fundamental principles of
physics?
Pollack thinks the computer did its own work because human
values--such as symmetry--were left out of the equations. And he
said they took pains to keep human input at a minimum.
"It doesn't know about the triangle, and it doesn't know about
the counterbalance any more than a bird knows about a wing," he
said. "It's simply exploiting those structures because the
physics makes them better."
The scientists see the experiment as a "baby step" on the road
to computer-driven machines--or robots--that evolve both
mechanically and "intellectually" as they work through
increasingly complex assignments.
"It's called evolutionary computation," Funes said, and it is an
attempt to copy the natural selection process that feeds
evolution in the world of plants and animals.
Like survival of the fittest, the Brandeis computer attaches one
Lego brick at a time, and discards the weaker for the stronger
combinations.
It doesn't mean Hal is lurking around the corner and planning a
coup, because the challenging field of robotics is progressing
at a very slow pace. The Brandeis computer might be able to
design a pretty good bridge, but it can't pick up a single Lego
brick.
"These are designed for an 11-year-old's hand," Pollack said.
"No one has a clue how to build a robot with that kind of manual
dexterity."
So the human body, as well as the mind, will undoubltedly remain
in control for a long time. But someday...