Today the FDA approved the marketing of Dean Kamen’s DEKA Arm, the robotic prosthetic arm affectionately known as the “Luke arm,” after Commander Skywalker’s famed replacement limb in The Empire Strikes Back. (Installed and poked by medical droid/action figure 2-1B, if memory serves.)
According to the FDA, the Luke arm is “the first prosthetic arm that can perform multiple, simultaneous powered movements controlled by electrical signals from electromyogram (EMG) electrodes.” The arm supports a variety of control inputs including wireless motion sensors that can be worn on the feet, EMG sensors, bump switches, and pull switches. These extensive connections to the wearer make the Luke arm potentially a game changer for amputees seeking to regain fine control of objects in the hand. In studies at the Veterans Administration, 90 percent of participants were able to perform complex tasks their previous prosthesis couldn’t handle: use keys and locks, prepare food, feed themselves, use zippers, brush and comb hair.
What do the arm’s makers have to say about it? We asked DEKA engineer Tom Doyon to tell us a little about the Gen 3 DEKA Arm that was approved today:
Who can forget the scene from The Empire Strikes Back when Darth Vader uses his light saber to cut off Luke Skywalker’s hand? As the movie closes, Luke gets a robotic hand that looks and moves like his original hand. Well, a team of engineers at Dean Kamen’s DEKA Research & Development Corp. has been working to make science fiction movie magic a reality for today’s upper limb amputees. With sponsorship from the Defense Advanced Research Projects Agency (DARPA) and the U.S. Army Research Office (ARO), the “Luke” project (as it is known inside DEKA) was formed to advance prosthetic arm technology.
The DEKA Arm, now in its third generation, is modular and configurable for different levels of amputation. In its maximum configuration, is has 10 powered degrees of freedom including a powered shoulder, elbow, wrist, and hand. The hand has six preprogrammed grips that are user-selectable. These grips are Power Grip, Tool Grip, Fine Pinch Open Grip, Fine Pinch Closed Grip, Lateral Pinch Grip, and Chuck Grip. Using a 2.4 GHz wireless interface with a proprietary protocol, a prosthetist can configure the arm system based on how the amputee wants to control the arm.
Developing an advanced prosthetic arm that is the same size, weight, and function of a natural limb wasn’t an easy task. There were many design challenges in developing the DEKA Arm. These include developing a configurable, non-invasive control scheme, keeping the weight of the arm equivalent to the “original equipment”, and getting all of the desired functionality into the required space.
Perhaps the most difficult engineering challenge in developing the DEKA Arm was the hand. Look at your hand when you move your fingers to pick a pen up off of a table; then imagine the challenge of fitting motors, mechanisms, gears, and electronics in the same space that can accomplish the same functions as your hand. To turn the group’s ideas into reality, the DEKA design team used a solid-modeling, 3D CAD system, SLS and SLA rapid prototyping systems to quickly prove concepts, and advanced manufacturing techniques to build the first systems.
Developing the DEKA Arm was very challenging and yet also rewarding for all those involved. They worked closely with and received design feedback from many upper-limb amputees. This valuable feedback helped the DEKA design team to quickly iterate and improve the design. In addition, it was very rewarding for the DEKA team to directly see the impact this arm has on amputee’s lives by witnessing the test subjects using the arm.
The science fiction movie world of Luke Skywalker is becoming a reality for today’s amputees.
Tom Doyon
Electrical Engineer
DEKA Research & Development Corp.
Manchester, New Hampshire
[1] The content of this article does not necessarily reflect the position or policy of the Government, and no official endorsement shall be inferred.
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