Development of Compliance Actuation Mechanism for Wire-Driven Robotic Hand Using Pressure Force

This paper presents a new actuation mechanism for a wire-driven robotic hand. The mechanism winds wire using friction force between the winder pulley and the wire instead of fixing the wire onto the pulley. If the wire is pulled over the maximum static friction force, the wire slips around the pulley. Therefore, the pulley and wire are protected from excessive stress. This mechanism uses a drum which presses the wire onto the pulley as a tensioner. This is different from conventional hands that use elastic material for maintaining constant tension of wire between a link and an actuator. The static model was analyzed using the Euler's belt formula, and the maximum friction force between the wire and pulley was obtained in order to design the proposed mechanism. Finally, the proposed method was added to a conventional hand, actuating dorsal and palmar flexion of its wrist. Tests were also conducted in order to confirm its feasibility as an actuation mechanism. As the result, we confirmed proposed mechanism can drive the joint and has compliance against external force.