F3Hand II: A Flexible Five-Fingered Prosthetic Hand Using Curved Pneumatic Artificial Muscles

Various five-fingered prosthetic hands have been commercialized and studied to support daily living of forearm amputees. However, most of them are more than 900 g because of several actuators and a complicated mechanism. In addition, they need a fitting mechanism because their fingers with high rigidity are difficult to fit various objects to be grasped. In this paper, we reported a five-fingered prosthetic hand termed as ”F3Hand II”. Flexible grasp and natural motions were achieved by using curved pneumatic artificial muscles (PAMs) as a skeleton and an actuator of its finger. Each finger of the hand had double joints to follow the movement of the PAM. Multiple degrees of freedom of the carpometacarpal (CM) joint in the thumb allowed various grasping patterns manually. Its weight including a socket was 245 g. We improved the durability of the finger joints, the interface of the drive unit, the mechanism of the wrist joint, the appearance of the F3Hand. An evaluation using a Southampton Hand Assessment Procedure (SHAP) test and a test on the manipulation of the daily objects demonstrated that an amputee was able to manipulate various objects.