Robot runs like humans
Technology Research News
robots have improved considerably in recent years. There are robots that
can walk, run and even play soccer, after a fashion. But humanoid robots
are still a long way from working alongside humans. A little jostling on
a crowded subway would leave today's humanoid robots flat on the ground.
Scientists have been making bipedal robots for years but have only
recently begun to use mathematical models to tackle the challenge of making
two-legged robots that walk and run without falling down.
Researchers from the Communications and Cybernetic Research Institute
of Nantes in France and the University of Michigan have developed mathematical
principals for enabling human-like running in bipedal robots, including
the ability to recover balance. They used the principals to develop control
software that allows a two-legged robot to run.
The software could also lead to improved prosthetic and robotic
The researchers' control algorithms achieve a stable running gait
in a two-dimensional bipedal robot dubbed Rabbit, said Jessy Grizzle, a
professor of electrical engineering and computer science at the University
Rabbit has a waist, two hip joints and two knees, but no upper body
or feet or ankles. The robot is free to fall forward or backward, but is
prevented from falling sideways by a rod that links its waist to a post
on the floor. This constrains the robot to walking or running in a circle.
Rabbit walks at an average speed of five kilometers per hour and
can run as fast as 12 kilometers per hour -- a 3 hour, 30 minute marathon
"Rabbit is designed to study principals of dynamic balance," said
Grizzle. "For this reason, Rabbit has no feet. Rabbit walks as if on stilts.
You can make a robot walk on stilts only if you really understand principals
of dynamic stabilization," he said.
A video on the researchers' Web site shows one of the researchers
giving Rabbit several shoves as it walks. Each time, Rabbit maintains its
balance and keeps walking.
The robot is part of an ongoing research project aimed at developing
robots that can execute a wide range of locomotion tasks, including walking,
walking while carrying a load, running and changing walking speeds, he said.
The researchers' running algorithm is a variation of their dynamic
walking algorithm. The main difference between running and walking is that
at one point during each running stride, both feet are off the ground. "Controlling
the motion of the robot when there is no contact with the ground is quite
a challenge," said Grizzle.
Running can be broken down into three phases: stance, which is when
a leg pushes off the ground, flight, which is when both feet are off the
ground, and impact, which is when the lead foot strikes the ground. The
researchers' algorithm calculates trajectories for each phase and links
them to form a closed loop.
The key to the algorithm's success is that it tracks events within
the loop rather than tracking time, so that if the robot's stride is altered
-- for example, by changes in terrain -- its joints respond to its position
in loop. This allows the robot to continuously adjust toward a stable gait.
The mathematical principals the researchers developed can also be
used to design better robots. "With our methods, we can directly determine
if a specific robot can be made to run at a desired speed or not, and if
not we can suggest ways to improve the robot's design so that it can run
faster or with greater stability," said Grizzle. "Having mathematical principals
removes a lot of the guesswork," he said.
The researchers are also aiming to use the technology to develop
better prosthetic devices and to develop robots that can act as rehabilitation
aids for people who have suffered neurological injuries. "Understanding
dynamic balancing in a machine is far simpler than in a human body, but
it is a good place to start," said Grizzle. "Now that we understand what
it takes to achieve stable walking in machines, we want to use that as a
springboard for helping recover this ability in people who have suffered
injuries," he said.
The researchers are working on active dynamic bipedal locomotion.
This differs from several teams of researchers that demonstrated passive
dynamic walking robots at the American Association for the Advancement of
Science annual meeting in February. (See "Humanoid robots walk naturally,"
TRN February 23/March 2, 2005)
Passive dynamic robots have unpowered joints and use little power.
In contrast, active dynamic robots use motors in each joint. "Rabbit has
big actuators at the knees and hips [and] is not very efficient at all,"
said Grizzle. However, "Rabbit is designed to be very agile," he said.
Both approaches are important for giving robots in the ability to
walk and run like humans. "We are working on opposite ends of the spectrum,
and it's anyone's guess who will arrive at the ultimate synthesis of these
results," he said.
The researchers' current work does not include side-to-side motion.
"Studying planar robots is an important step toward the understanding of
three-dimensional robots," said Grizzle.
The researchers' dynamic balancing technology could be used for
designing better robotic control systems now, but is not likely to be used
for another two to five years, said Grizzle. Medical applications could
be practical in five to ten years, he said.
Grizzle's research colleagues were Christine Chevallereau of the
Communications and Cybernetic Research Institute of Nantes and Eric Westervelt,
who is now at Ohio State University. The researchers presented the work
at the IEEE Conference on Decision and Control held December 14 to 17, 2004
in Paradise Island, Bahamas. The research was funded by the National Science
Foundation (NSF) and the French National Center for Scientific Research
Timeline: Now, 5-10 years
TRN Categories: Robotics
Story Type: News
Related Elements: Technical paper, "Asymptotically Stable
Running for a Five-Link, Four-Actuator, Planar Bipedal Robot," paper
June 15/22, 2005
Robot runs like humans
DNA machine links molecules
Process ups biodiesel
It Works: Power sources
Lens boosts LED efficiency
boosted to 2 GHz
Single camera measures
Research News Roundup
Research Watch blog
View from the High Ground Q&A
How It Works
News | Blog
Buy an ad link