HIT prosthetic hand based on tendon-driven mechanism

An underactuated finger structure actuated by tendon-driven system is presented. Kinematics and static analysis of the finger is done, and the results indicate that the prosthetic finger structure is effective and feasible. Based on the design of finger, a prosthetic hand is designed. The hand is composed of 5 independent fingers and it looks more like humanoid. Its size is about 85% of an adult's hand and weights about 350 g. Except the thumb finger, each finger is actuated by one DC motor, gear head and a tendon, and has three curling/extension joints. The thumb finger which is different from other existing prostheses is a novel design scheme. The thumb finger has four joints including three curling/extension joints and a joint which is used to realize the motion of the thumb related to the palm, and these joints are also driven by one DC motor, harmonic drive and a tendon. The underactuation and adaptive curling/extension motion of the finger are realized by joint torsion springs. A high-powered chip of digital signal processing (DSP) is the main part of the electrical system which is used for the motors control, data collection, communication with external controlling source, and so on. To improve the reliability of the hand, structures and sensors are designed and made as simply as possible. The hand has strong manipulation capabilities that have been verified by finger motion and grasping tests and it can satisfy the daily operational needs and psychological needs of deformities.