A study by engineers at Oregon State University (OSU) suggests that they have achieved one of the most realistic robotic implementations of human walking dynamics, which may allow human-like versatility and performance.

The system is based on a concept called "spring-mass" walking that was theorized less than a decade ago, which combines passive dynamics of a mechanical system with computer control. It provides the ability to blindly react to rough terrain, maintain balance, retain an efficiency of motion and essentially walk like humans do.

Engineers have successfully field tested their walking robot, known as ATRIAS. Inage source: Oregon State University.The findings on spring-mass walking have been reported for the first time in IEEE Transactions on Robotics. The work was supported by the National Science Foundation, the Defense Advanced Research Projects Agency and the Human Frontier Science Program.

The technologies developed at OSU have evolved from intense studies of both human and animal walking and running, to learn how animals achieve a fluidity of motion with a high degree of energy efficiency. Animals combine a sensory input from nerves, vision, muscles and tendons to create locomotion that researchers have now translated into a working robotic system.

The system is also efficient. Studies done with their ATRIAS robot model, which incorporates the spring-mass theory, showed that it is three times more energy-efficient than other human-sized bipedal robots.

Jonathan Hurst, an OSU professor of mechanical engineering and director of the Dynamic Robotics Laboratory in the OSU College of Engineering, says that "other robotic approaches may have legs and motion, but don't really capture the underlying physics.” The researchers say they are convinced this is the approach on which the most successful legged robots will work. It retains the substance and science of legged animal locomotion, and animals demonstrate performance that far exceeds any other approach they have seen. “This is the way to go," Hurst says.

The robots being constructed at OSU were designed to mimic the "spring-legged" action of bipedal animals. With minor variations, muscles, tendons and bones form a structure that exhibits most of the required behavior, and conscious control just nudges things a little to keep it going in the right direction. The effort is smooth and elastic, and once understood, can be simulated in walking robots by springs and other technology.

ATRIAS, the human-sized robot created at OSU, has six electric motors powered by a lithium polymer battery about the size of a half-gallon of milk, which is smaller than the power packs of some other mobile robots.

Researchers say that this technology "has the potential to enhance legged robots to ultimately match the efficiency, agility and robustness of animals over a wide variety of terrain."

In continued research, work will be done to improve steering, efficiency, leg configuration, inertial actuation, robust operation, external sensing, transmissions and actuators, and other technologies.