Load-sensitive continuously variable transmission for robot hands

This paper presents a load-sensitive continuously variable transmission (CVT) for finger joints. The fingers of a robot hand require power 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, a remarkably simple and small load-sensitive CVT can be developed based on a crank CVT. The mechanism consists of a five-bar linkage and a torsion coiled spring. We have developed one joint with the CVT and have experimentally verified that the CVT can increase its reduction ratio from 0.5 to 3.3 in response to a load.