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New strides made with robots' walks
By ALEXANDRA WITZE Science Writer
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Doing the robot dance may soon be more outdated than ever - researchers have found a way to transform the jerky gait of robots into a more fluid, humanlike motion.
Three new robots are the closest yet to mimicking how people really walk, said the scientists who unveiled the machines publicly for the first time last week. All three use a basic human motion - the leg swinging gait known as "passive dynamic walking" - to consume as little energy as possible.
One day, such robots could lead to better prosthetics for disabled people, or perhaps a better understanding of how the human gait evolved, said Steve Collins, an engineering student at the University of Michigan and developer of one of the machines.
The robots were demonstrated at the national meeting of the American Association for the Advancement of Science. A report on the research appeared last week in the journal Science.
None of the new robots can compete in style with Japan's flashy Asimo robot, the world's most advanced humanoid machine. Honda, Asimo's creator, uses the robot to impress clients and spread the word about robotics during international tours.
Unlike Asimo, the new robots can't stand up, sit down or even turn sideways. One is just a pair of mechanical metal legs, with stumpy arms and ping-pong ball eyes glued to the front. Another is a small "toddler" robot, about the size of a large doll and festooned with wires. The third looks like a small metal human, but with an empty blue bucket on its head to show just how unintelligent it really is.
Yet all three share the passive dynamic mode of walking, which is the most energy-efficient way for a two-legged creature to move, said Andy Ruina of Cornell University.
Passive dynamics simply means that two legs, attached to hips and allowed to swing freely, can produce a natural-looking, if slow, downhill waddle. Nineteenth-century toys, such as small wooden penguins, used this simple trick to amuse generations of children, Dr. Ruina said in Washington during a meeting of the American Association for the Advancement of Science.
"Just sticks and hinges, walking downhill, produces a very humanlike gait," he said.
That kind of walking takes no power, but things get tougher for a robot faced with flat - not downhill - ground. So the three research teams added small motors to their robots to replace the pull of gravity.
Mr. Collins's robot, developed while he was a student at Cornell, has batteries in its arms that power springs in its "ankles." It loses energy only during its transition between steps, making it at least 10 times as efficient as other robot designs, Dr. Ruina said.
A second machine, made at Delft University of Technology in the Netherlands, uses a gas canister to power artificial muscles at its hip. Like the Cornell robot, it uses very simple controls to accomplish basic walking.
More complicated is the toddler-sized robot created at the Massachusetts Institute of Technology. As it walks, small sensors onboard take measurements 200 times a second on how fast it is going, in what direction and other factors. A nearby computer, linked to the robot wirelessly, calculates how it is doing and makes adjustments accordingly - perhaps bringing it upright if it starts to tip, or taking smaller steps if required.
In essence, the MIT robot is an intelligent machine that learns on the fly, said its co-creator, Russ Tedrake. Starting from scratch, it can teach itself how to walk within 20 minutes, or about 600 steps.
With more work, the toddler bot could become the basis for a next generation of newer, more efficient robots, he said.
"In 20 to 30 years, I think you'll see robots everywhere," he said.
Energy efficiency is important because current robots, like the Asimo, are limited mostly by battery lifetime. If a machine could move while using much less energy, it could run for a much longer time, Dr. Ruina said.
The energy-saving moves could also help build better prosthetics, with less wear and tear over time. Mr. Collins, for example, is using some of the lessons from robots to develop a powered prosthetic foot for amputees.
E-mail awitze@dallasnews.com
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