Researchers at the Georgia Institute of Technology have created an ultrasonic sensor that allows people with amputations to control each of their prosthetic fingers individually. It provides fine motor hand gestures that aren’t possible with current commercially available devices, according to the researchers.
“Our prosthetic arm is powered by ultrasound signals,” said Gil Weinberg, a Georgia Tech College of Design professor and director of the Center for Music Technology, who leads the project. “By using this new technology, the arm can detect which fingers an amputee wants to move.”
The first person to work with Weinberg’s technology was musician Jason Barnes, who was electrocuted during a work accident in 2012, which resulted in a transradial amputation of his right arm. The ability to individually control his prosthetic fingers allowed him to play the piano for the first time since his amputation.
Barnes’ usual prosthesis is controlled by EMG sensors attached to his muscles.
The arm has an ultrasound sensor, allowing it to watch the muscles as they move.
Photograph courtesy of Georgia Tech
“EMG sensors aren’t very accurate,” Weinberg said. “They can detect a muscle movement, but the signal is too noisy to infer which finger the person wants to move. We tried to improve the pattern detection from EMG for Jason but couldn’t get finger-by-finger control.”
Weinberg’s team partnered with Georgia Tech College of Sciences professors Minoru Shinohara, PhD, and Chris Fink, and Levent Degertekin, PhD, of the Woodruff School of Mechanical Engineering to attach an ultrasound probe to Barnes’ arm, allowing them to watch how Barnes’ muscles moved.
When Barnes tried to move his prosthetic ring finger, the muscle movements differed from those seen when he tried to move other digits. Weinberg and the team fed each unique movement into an algorithm that is designed to quickly determine which finger Barnes wants to move. The ultrasound signals and machine learning can detect continuous and simultaneous movements of each finger, as well as how much force he intends to use.
This is the second device Weinberg’s lab has built for Barnes. The team fitted him with a prosthetic arm with two drumsticks in 2014. He controlled one of the sticks and the other moved on its own by listening to the music and improvising.
“If this type of arm can work on music, something as subtle and expressive as playing the piano, this technology can also be used for many other types of fine motor activities such as bathing, grooming, and feeding,” Weinberg said. “I also envision able-bodied persons being able to remotely control robotic arms and hands by simply moving their fingers.”
Editor’s Note: This story was adapted by materials provided by the Georgia Institute of Technology
