Design of a Tendon-Driven Articulated Finger-Hand Mechanism and Its Stiffness Adjustability

Abstract

This paper describes design of a tendon-driven articulated finger hand that has similar properties to those of a Remote Compliance Center (RCC) device, i. e., it generates resolved displacements for disturbance forces applied to a grasped object and it can also adjust the elastic coefficients semiactively using the nonlinear elasticity of tendons. After introducing some basic results with respective to a tendon-driven mechanism, the stiffness matrix which relates the restriction forces applied to a grasped object to the small displacements of the object is derived. It is shown that more than six tendons are necessary, for each finger to adjust all elements of the stiffness matrix using only the nonlinear mechanical elasticity of tendons. After that, the wiring and pulley system is designed that cannot only drive the fingers freely without loosing the tension forces but also can diagonalize the stiffness matrix and adjust the elements. It is also shown that the hand can grasp different sized objects without losing the property using the tendon redundancy.