DOD Working Toward Fully Functional Prosthetic Arms

By Rob McIlvaine

NATIONAL HARBOR, Md.  — A robotic arm, dubbed “Luke,” after the Jedi with the mechanical hand, served as the centerpiece for a Jan. 31 discussion here regarding advancements in prosthetics.

The robotic arm is a Defense Advanced Research Projects Agency-funded project, in partnership with the Department of Veterans Affairs. The goal of the project is to restore functionality for individuals with upper extremity amputations. The project is still in development.

“The original goal for the program, back when we got started in 2005, was to create, within this decade, a fully functional motor and sensory upper limb that responds to direct neural control,” said Dr. Stewart Coulter, during the 2012 Military Health System Conference at the Gaylord National Hotel and Convention Center, from Jan. 30 to Feb. 2.

Coulter, who serves as the general manager at DEKA Research and Development Corporation in Manchester, N.H., also has the role of product manager for the revolutionizing prosthetic arm system to provide improvements in functionality and usability for wounded warriors and others.

The DEKA arm has 10 degrees of movement, and features moving fingers, wrist, elbow and shoulder. All those parts move with electric motors, which are controlled by the user with signals from a foot-based controller.

But Coulter said it’s easy to confuse the advances being made in prosthetics with science fiction.

“A lot of people have seen, for instance, the Terminator movies, and sometimes forget that those aren’t actually real,” Coulter said.

The standard for prosthetic arms up until now has been “two to three degrees of freedom,” Coulter said, which is not much different than a prosthetic arm that features a hook.

“You see the hand open and close, you’re seeing elbow flex, you might see a wrist rotate but not much more than that,” Coulter said. “You’re seeing low torque, but you’re not seeing any feedback to the user.”

In addition to degrees of freedom in prosthetic movement, Coulter said work being done to combine multiple individual prosthetic movements into single, more fluid movements. He also said there is work being done to find better ways to attach prosthetics to the user’s body.

“These are the three areas that need to be resolved,” he said. “If you can’t address making the arm have the capability, if you can’t address the control seam part, if you can’t address how you attach it to them, it won’t do any good to address two of the three.”

The various grips are also important.

“If you want to be able to use a drill, there’s a whole different grip,” Coulter said. “So now we have a grip that will let you close the index finger independently like that. And you ought to see somebody’s face light up who hasn’t used a drill in 20 or 30 years.”

One of the hard parts about this, he said, is finding a way to control a system, given the fact there’s now 10 degrees of freedom in the arm.

“Current ones are done with myoelectric controls, so they’ll use residual muscles and it’s very difficult to do that,” he said. With the DEKA arm, they are using foot-based controls.

“This provides a pretty good level of control, without relying on someone else to do it, relying on a joy stick, or relying on using their other arm to control it,” he said.

Coulter said his team works very closely with a number of people who have used the arm system, and he says they’ve let the team know what works, and what needs to be fixed.

“We’ve done clinical studies over the life of the program to improve design and to confirm we got it right,” he said. They now have more than 4,000 hours of use time on versions of the arm system.

“This has really given us the experience with the people who’ll have to use it,” he said.

Coulter said it’s fun to have a group of engineers sit and design something but even more fun to have people use it.

“It’s been tremendous to work with them and give them the chance to say what activities they want to do,” he said. “We’ve let five people take it home for two weeks, see what they think of it, come back and tell us what’s going on.”

The feedback, he said, has been very positive.

“They want to do the things that are important to them, such as, going out to a restaurant and eating with chopsticks or a fork, playing golf, holding a trumpet and playing it, leaning up on a lamppost with an outstretched arm, holding a baseball, or reaching up to the top shelf and picking up a glass of water and holding it level as it’s brought down to drink,” he said.

“To hear them say, ‘Yes, I can use this for things I couldn’t get done before,’ is exactly what we’re pushing for here,” Coulter said.

This article first appeared on Army.mil.