Man with Bionic Prosthetics  (Source: The Johns Hopkins University Applied Physics Laboratory )

Bionic Prosthetic on Workbench  (Source: The Johns Hopkins University Applied Physics Laboratory )
Researchers focus on control of new artificial limbs without conscious thought

Researchers at Johns Hopkins have spearheaded a nationwide effort to bring artificial limb technology up to standards that would make the limbs a better replacement for the natural limbs that are lost to trauma.

The research is funded by DARPA and is on a four year plan to bring new high-technology bionic arms to amputees. DARPA has spent $30.4 million on the artificial limb project to date. The new technology under research will allow amputees to more naturally control artificial limbs and to actually feel what they are holding as well as feel the temperature of things the artificial limb is holding.

To help bring the new artificial limbs to fruition DARPA split the four year plan into a pair of two-year projects intended to yield the limbs by 2007 with goal of bringing the technology to the world by 2009. The first product from the research was an artificial arm developed in 2007 called Proto-1 that had eight joints with eight degrees of freedom.

The second prototype resulting from the research was called Proto-2 and was started in 2007. Proto-2 has 25 joints with 25 degrees of freedom. Proto-2 has 15 motors in the hand alone providing finger movement and almost natural levels of dexterity.

The real work for the project of the next generation of prosthetic limbs is to allow the user to control the limbs without having to concentrate on movements specifically. One researcher describes the problem of controlling a prosthetic limb:

Think about taking a sip from a can of soda. The complex neural feedback system connecting a native limb to its user lets that user ignore an entire series of complicated steps. The nervous system makes constant automatic adjustments to ensure, for example, that the tilt of the wrist adjusts to compensate for the changing fluid level inside the can. The action requires little to no attention. Not so for the wearer of current prosthetic arms, for whom the act of taking a sip of soda precludes any other activity. The wearer must first consciously direct the arm to extend it to the correct point in space, then switch modes to rotate the wrist into proper position. Then he must open the hand, close it to grasp the soda can (not so weakly as to drop it but not so hard as to crush it), switch modes to bend the elbow to correctly place the can in front of his mouth, rotate the wrist into position, and then concentrate on drinking from the can of soda without spilling it.

Getting greater control over a prosthetic limb requires different levels of invasiveness for the control apparatus. The first level allows for large muscle control, but no finger control. This can be accomplished by electrodes placed on the skin. The second level of control allows for fine motor control and finger movement and requires electrodes to be put directly into the muscles.

The third level of control allowing control of limbs with unconscious effort like a natural limb for some users of the new prosthetic limbs would require surgery to implant electrodes directly into nerves and muscle.

Researchers say that it may require a combination of these types of controls to provide the most natural limb movement. If the researchers can bring prosthetic to amputees with levels of control rivaling their natural limbs it will change the lives of amputees around the world. DailyTech reported in July of 2007 about a Chinese man using a type of bionic legs to regain his mobility after an accident resulted in the loss of the lower half of his body.

"I'd be pissed too, but you didn't have to go all Minority Report on his ass!" -- Jon Stewart on police raiding Gizmodo editor Jason Chen's home
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