Walking Robots on Display in Science and at AAAS Annual Meeting

Toddler rocks to the left, picks up his right foot and puts it down, then rocks to the right, picks up the left foot and puts it down. As his arms swing in rhythm with his feet, Toddler advances steadily forward, then backward. The wobbling gait is familiar to anyone who's watched a baby learning to walk, but from his lithium polymer batteries to his nylon ankles, Toddler is very much a robot.

Toddler and the scientists behind a new breed of bi-pedal robots that are designed to walk on "passive-dynamic" principles—much like humans, in other words—put on an exhibition of their amazing technology as the AAAS 2005 Annual Meeting got underway Thursday 17 February in Washington, D.C.

Scientists Andy Ruina of Cornell University and Steven Collins of the University of Michigan (and formerly of Cornell) have pioneered the development of robots that can walk down a slight slope without outside power, and on the development of highly efficient motorized walking robots.

Toddler is different, says Russ Tedrake, a postdoctoral associate at MIT's Department of Brain and Cognitive Sciences. Though he's only 43 centimeters tall and weighs about four kilograms, he uses more energy. But backed a 700-megahertz Pentium computer in his belly, he has the power to learn and adapt on the fly.

"We think that in the very near future, we're going to see these robots walking over terrain they haven't seen before," Tedrake told reporters at a AAAS news briefing.

The robots are the subject of path-breaking paper in the 18 February edition of Science.The paper is authored by Tedrake, Ruina, Collins, and Martijn Wisse of Holland's Delft University of Technology.

The engineering advances evident in Toddler and in the robots developed at Cornell and Delft could have broad applications. The research could aid scientists' understanding of the human motor system; already the lessons are being applied to research into "intelligent prostheses." In the future, the new research could change the way humanoid robots are designed and controlled. Some scientists see bi-pedal robots possibly working with hazardous waste or replacing live astronauts in space exploration.

Passive-dynamic robots were first developed in the late 1980s. They differ sharply from Honda's space-age Asimo robot, a polished and sophisticated machine that can walk and jog. Asimo's every move is controlled by computers and motors, giving it remarkable skills but requiring considerable energy.

The robots developed at MIT, Cornell, and Delft are more primitive in look. The revolution is in the mechanics of motion. "We let the mechanics take care of a lot of the motion rather than use motors to create the motion," Ruina told reporters.

The robots featured in Science and at the AAAS news briefing are each different in their look, their engineering and their energy efficiency, but all are modeled after walking toys that have been around since the 19th century. Those antique "passive-dynamic" toys can walk down a shallow slope without any motors.

The robotic research followed the example of the Wright Brothers, who first studied gliders and then added a motor to achieve powered flight.

With the use of motors, the robots are able to walk with relative ease, unaided by a slope. Toddler's computer system allows the robot to teach itself to walk in less than 20 minutes, or about 600 steps. Among other things, Tedrake says, the learning program allows the robot to navigate efficiently over a variety of walking surfaces, and may eventually allow robots to navigate very rough terrain.

Each of the three has different engineering for forward propulsion. The MIT robot has motors that move the ankle. The Delft robot uses a pneumatic push at the hip. The Cornell robot has a microchip controller that tells the rear foot to push off, a moved timed closely with the front foot hitting the ground.

The research was funded by the U.S. National Science Foundation, the Dutch Technology Foundation (Stichting Technische Wetenschappen-STW) and the Packard Foundation.

In a news release, Michael Foster, an NSF expert on computer and information science and engineering and one of the managers who oversaw this research, called the innovations "the foundation for what we may see in robotic control in the future."

"This is a perfect example of a single concept yielding benefits in a variety of fields, including medicine," added NSF program officer Gil Devey, an expert on disabilities research who also oversaw the projects.

— Edward W. Lempinen

17 February 2005