Design of a Novel Locking Ratcheting Mechanism for a Body-Powered Underactuated Hand

Abstract As affordable and efficient three-dimensional (3D) printers became widely available, researchers are focusing on developing prosthetic hands that are reasonably priced and effective at the same time. By allowing anyone with a 3D printer to build a body-powered prosthetic hand, many people could build their own prosthetic hand. However, one of the major problems with the current designs is the users must bend and hold their wrist in an awkward position to grasp an object. The primary goal of this work is to present the design process and analysis of a body-powered underactuated prosthetic hand with a novel ratcheting mechanism that locks the finger automatically at a desired position. To estimate how a compliant finger behaves on the actual system with the ratcheting mechanism, the preshaping analysis and the preshaping experiment were conducted. From the experiment, the presence of elastic hysteresis was observed. Additionally, the contact force analysis was performed to see the effects of joint angles and applied tension force. To test how well the hand can grasp, a cup with various weights was lifted and various objects with different shapes were grasped to prove how well the compliant finger can adapt to the shape of the objects. Based on the experiment, the hand had a higher success rate of grasping objects that are lightweight (less than 500 g) and cylindrical or circular shaped.