Igrasp hand: a biomimetic transradial robotic hand prosthesis with a clutching mechanism

Abstract

This paper proposes a nineteen degrees of freedom transradial robotic hand prosthesis, named iGrasp Hand. The device consists of three units: clutching unit, wrist unit and hand unit. Fingers of the iGrasp Hand are actuated by six motors, coupled to an under-actuated tendon-based mechanism. A novel clutching mechanism, installed with one-way bearings, is introduced to achieve passive isometric contraction of fingers during grasps. Palmar arching is facilitated by the addition of carpometacarpal joints in the ring and little fingers. A mathematical model is formulated to analyse finger motion and a prototype is fabricated for experimental testing. Moreover, a position control algorithm is implemented to achieve targeted grasping patterns. Several experiments were carried out to evaluate the effectiveness of the device. The results reveal the capability of iGrasp Hand in achieving twelve grasping patterns, ranging from power to precision grasps. The palmar arching and opposition/re position movement of the thumb allows the grasping of smaller objects. Furthermore, the potential for reducing energy consumption during the isometric hold was investigated. The iGrasp Hand can perform over 70% of activities-of-daily-Iiving and mimic the human hand with an anthropomorphism mobility index of 40%.