Human Mimetic Forearm Mechanism for Bionic Arm

Abstract

In this thesis, we describe the motion mechanism of the bones when the human arm performs pronation and supination and simulates the movement of the bones through the mechanical elements and experiment with prototypes. We have applied it to prosthesis as an application to verify the mechanism. The P/S motion of the existing robotic prosthesis showed a distinctly different movement from that of the human. This is primarily a cosmetic completely, and making it to look like a normal person is one of the most important issues for the patients. The second issue is the disharmony of users as a different motion. The human P/S motions do not simply rotate like a robot wrist. In this paper, we have developed the mechanism that shows the same P/S motion as if human. Based on several references, we have known that the spatial-four-bar mechanism is one of the best descriptions for human forearm movement. Prior to the actual design, 3D data of the human arm were measured using MRI and 3D scanner to obtain design parameters. Through the measured data, the link lengths, joint positions, and skin shape data were obtained. Next, mathematical analysis were conducted to simulate one degree of freedom P/S motion from the spatial four-bar, and the results of simulations acting like human arm bones were obtained as a consequence of substituting the previously obtained human design parameters. Since the prosthesis is attached to a human arm, a socket is required to connect between arm and the prosthesis. In this thesis, we are to develop two types of sockets: elbow-attached-socket and body-powered-socket. The elbow-attached-socket was designed to fit the wearer's arm using the shape data of the skin. Next, the body-powered-socket, which transmits the input torque to the mechanism, is designed to be fixed to the bone, in otherward, it is designed using the HiFi concept. Thus, we test whether the P/S motion works well through the developed prosthesis, and verify the effectiveness of the ADL experiment for the ultimate purpose "to use in real life’.