London, September 6 : Scientists have created a new design for robot legs, which would involve the use of steel cable tendons and built-in springs, to remove the hindrance that robotic machines face while walking.
One of the greatest barriers facing roboticists is the art of walking.
Legs with joints driven by motors struggle to recycle energy during walking in the way biological legs with springy tendons and muscles do.
But, according to a report in New Scientist, a new design driven by steel cable tendons and with built-in springs could provide the answer.
"The spring is important. That's something that is fundamental to being able to run in an efficient way," said Jonathan Hurst, a roboticist at Oregon State University, Oregon.
Studies of humans walking and running show that our tendons and muscles store and release up to 40 per cent of the total energy expended. Other animals, for example kangaroos, recycle even more.
Programming the motors in a robot leg to produce a springy gait is possible, but they waste a lot of energy doing it and results are poor, according to Hurst.
Hurst's robot legs use actual springs to store and release energy. The most advanced is called the Electric Cable Differential Leg - a single leg with a knee joint.
The body of the leg contains motors that drive the knee indirectly using metal cables, and two fibreglass springs made from the same material as archers' bows. The springs store and release energy as the leg hops.
Hurst created three of the robot legs while a student at Carnegie Mellon University in Pittsburgh. One of them, called Thumper, joined him for his new appointment at Oregon State and is attached to a boom that prevents it from falling left or right, but not to the front or back.
Two others, teamed up to build a biped called MABEL, are at the lab of Hurst's collaborator, Jessy Grizzle, at the University of Michigan in Ann Arbor.
The springs inside each leg can store a kilojoule of energy per kilogram, enough that a 75-gram spring can easily store the energy required for a single hop.
To get the required power from a motor alone would require a motor that weighed 30 times as much as the spring.
Grizzle is working on the control algorithms that give these robots a sense of balance.
He said that the bipedal robot MABEL walks well on even ground. The next step is to get it to walk well on uneven terrain, and eventually to run.
"That's where the springs will help us a lot, walking on rough ground. There's a natural shock absorber there," he explained. "MABEL is a leap in advanced leg design and will help researchers to create running robots with more efficient, animal-like gaits," he added.