Underactuation between the Fingers

Introduction

Common robotic hands do not usually comprise one single finger, except maybe in tentacle inspired systems. The prototypes presented in Table 2.1 have a number of fingers comprised between two and five, while over 50% have three fingers. It is therefore a natural step to extend the principle of underactuation to the hand itself in addition to individual fingers. The purpose of the underactuation between the fingers is to use the power of one actuator to drive the open/close motion of all the fingers of a robotic hand collectively. The transmission mechanism must be adaptive, i.e., when one or more fingers are blocked, the remaining finger(s) should continue to move. When all the fingers are blocked, the force should be well distributed among the fingers and it should be possible to apply large grasping forces while maintaining a stable grasp. Introducing underactuation between the fingers of a robotic hand allows to further reduce the complexity of the systems, from the actuation point of view.