Losing a limb can be a devastating experience, and while electrically powered prostheses can serve as a replacement for a lost arm, they are notoriously difficult to operate, and will never fully replace normal hand function.
Researchers at the Norwegian University of Science and Technology (NTNU) are working to improve this situation through the use of smartphone technology. The technology, called an accelerometer, gives users a better sense of the orientation of their artificial limb — thus making the limb easier to operate.
A helping hand
An accelerometer is a tool for detecting changes in gravity or velocity, and enables a device to determine its orientation. Accelerometers are relatively inexpensive, and are widely used in everything from video consoles to smartphones. The accelerometer in your smartphone helps it determine whether you want to look at a photograph in a portrait or landscape format, for example.
Øyvind Stavdahl, an associate professor at NTNU’s Department of Engineering Cybernetics and Anders Fougner, a PhD candidate in the department, have shown that when an accelerometer is used in a prosthetic arm, it is easier for the user to recognize exactly how the arm is oriented in space.
“Prostheses are driven by the remaining muscles in the severed limb. Sometimes, however, the prosthesis receives atypical signals from the muscles, which can confuse the system and lead to the prosthesis performing the wrong movement,” Stavdahl says. “Knowing the orientation of the arm is essential for normal prosthetic function. It simply makes it a lot easier to operate.”