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One small leap for running robots

Steadier gait Swiss robotics researchers have made a small step towards the holy grail of getting robots to run like humans.

Harold Roberto Martinez Salazar and Juan Pablo Carbajal of the University of Zurich's Artificial Intelligence Laboratory report their mathematical analysis in a recent issue of Physics Review E.

"The hot question is how we make robots that can run as effectively as humans do," says Queensland University of Technology professor of robotics, Dr Gordon Wyeth, of the research.

"This is a small step on the way."

Unlike what we see at the movies, current bipedal robots are a long way from outrunning humans and leaping onto buildings.

In fact, says Wyeth, the fastest running robot does little more than a "quick shuffle".

"Technically it is running because both feet are in the air, but only very briefly," says Wyeth.

"Most two-year-olds could pretty effectively outrun these robots."

One of the challenges for those trying to build robots that walk and run like humans is making sure they don't fall over and don't use too much energy.

"When Asimo [a bipedal robot] walks it uses the same amount of energy as an Olympic runner would use running 100 metres," says Wyeth.

Slazar and Carbajal enhanced a model currently used to design bipedal robots to help address this challenge.

Inverted pendulum

The model used by Slazar and Carbajal likens walking legs to an inverted pendulum.

The first leg falls to a particular angle before it is stopped by the foot of the other leg striking the ground.

In a "stable" state of walking, there is enough energy in the system to keep the second leg moving foward so it too starts falling and keeps the cycle going.

There is also a side to side movement that is necessary to make sure the centre of gravity is over the foot that strikes the ground.

The inverted pendulum model can also be adapted for running, in which the legs are likened to an inverted pendulum loaded with springs.

Wyeth says to go from the stable state of walking to the stable state of running requires a kick of energy.

Slazar and Carbajal characterised the angle and speed of legs in stable walking and stable running and also worked out how best to change a robot's gait so it changes from one state to the other using the least amount of energy.

"The work is giving us a deeper understanding of what's going on in running and walking so that we might be able to build more stable, more energy efficient humanoid robots in the future," says Wyeth.

He says the many differences between robots and humans mean it is not possible to directly apply the latest findings to humans, although the findings may have some relevance to the field of biomechanics.