A bionic leg which responds to muscular signals

April 21st, 2011 - 5:54 pm ICT by IANS  

London, April 21 (IANS) As Hailey Daniswicz flexes her thigh muscles, electrodes attached to her send messages to a computer avatar to flex its knee and ankle — parts of her leg missing for six years.

Daniswicz is training the computer to recognize slight movements in her thigh so she can eventually be fitted with a ‘bionic’ leg.

She would then be able to control the robotic prosthesis with her own nerves and muscles.

The 20-year-old sophomore at Northwestern University, who lost her lower leg to bone cancer, is part of a clinical trial sponsored by the US Army.

The tests are using electromyography - electrical signals produced by muscles — and pattern recognition computer software to control a new generation of robotic limbs, the Daily Mail reports.

Electrodes attached to nine different muscles in the thigh act as antennas, picking up electrical signals sent from the nerves to the muscles. These signals are fired in a specific pattern depending on how a person intends to move.

With a bit of training, the computer can learn a person’s signal pattern for when they want to bend a knee or flex an ankle and it makes the virtual reality avatar move.

“We’re really integrating the machine with the person,” said Levi Hargrove, a research scientist at the Rehabilitation Institute of Chicago’s Center for Bionic Medicine in the US.

“The way most prosthetics work now is you have mechanical sensors. You have to push and interact with them,” said Hargrove, who is leading the project. “With this, you measure the actual neural intent and have that tell the motor what to do.”

Researchers at the institute have already developed prosthetic arms directed by nerve impulses. But a robotic leg would give lower limb amputees a new kind of freedom, allowing them to climb stairs more safely and with more natural motion.

There are roughly two million lower leg amputees in the world, but that figure is expected to double by 2050 as the number of people with diabetes increases.

Daniswicz has been training her computer avatar since January and she can now instruct it to bend and straighten its knee, and flex and straighten its ankle, just by making slight movements in her thigh muscles.

Hargrove said: “Hailey has taught the computer what to do, and now, whenever she does it, it listens, interprets and makes the leg on the virtual reality avatar move.”

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