3D Printed Prosthetic Hand Can Guess How You Play Rock, Paper, Scissors

“The patient just thinks about the motion of the hand and then the robot automatically moves. The robot is like a part of his body. You can control the robot as you want. We will combine the human body and machine like one living body.” explains Tsuji.

Electrodes in the socket of the prosthetic equipment measure electrical signals from nerves through the skin— similar to how an ECG measures heart rate. The signals are sent to the computer, which only takes five milliseconds to make its decision about what movement it should be. The computer then sends the electrical signals to the motors in the hand.

The neural network (named Cybernetic Interface), that allows the computer to “learn”, was trained to recognize movements from each of the 5 fingers and then combine them into different patterns to turn Scissors into Rock, pick up a water bottle or to control the force used to shake someone’s hand.

“This is one of the distinctive features of this project. The machine can learn simple basic motions and then combine and then produce complicated motions.” Tsuji says.

Seven participants were recruited for this study, including one amputee who had worn a prosthesis for 17 years. Participants were asked to perform a variety of tasks with the hand that simulated daily life, such as picking up small items, or clenching their fist. The accuracy of prosthetic hand movements measured in the study for single simple motion was above 95 %, and complicated, unlearned motions was 93%.

However, this hand is not quite ready for all wearers. Using the hand for a long time can be burdensome for the wearer as they must concentrate on the hand position in order to sustain it, which caused muscle fatigue. The team are planning on creating a training plan in order to make the best use of the hand and hope it will become an affordable alternative on the prosthetics market.

Contacts and sources:
Hiroshima University
https://www.hiroshima-u.ac.jp/en

Citation: A myoelectric prosthetic hand with muscle synergy-based motion determination and impedance model-based biomimetic control, Akira Furui, Shintaro Eto, Kosuke Nakagaki, Kyohei Shimada, Go Nakamura, Akito Masuda, Takaaki Chin, and Toshio Tsuji,  Science Robotics, Vol. 4, Issue 31, eaaw6339, DOI: 10.1126/scirobotics.eaaw6339, 26 June 2019.