Load-Sensitive Continuously Variable Transmission for Robot Hands

Abstract

This paper presents a load-sensitive continuously variable transmission (CVT) for finger joints. Fingers of robot hands require force when grasping an object and speed when opening and closing. Therefore a CVT is ideal to improve the power transmission of a finger joint. Existing friction CVTs are too big and heavy to be installed in a finger joint. By focusing on the fact that finger joints do not necessarily rotate 360 degrees, this paper presents a remarkably simple and small load-sensitive CVT consisting of a five-bar linkage and a torsion coiled spring. Experimental results show that the CVT can increase its reduction ratio from 0.5 to 3.3 in response to a load. We have developed a two-finger gripper with the CVTs, which can grasp an object powerfully and manipulate quickly. These motions would be impossible without the CVT.