Experimental study on grasp force control characteristics of a human.

Abstract

This paper considers the human grasping ability experimentally. The motivation for this work is to enable a robot hand to grasp an object of unknown weight. We begin with an examination of human behavior of shaking an object up and down using thumb and middle finger. Experimental results show that the human varies a grasp force to compensate for the inertial force of the object, and use his slip sense to generate a grasping force just greater than the minimum required for grasping the object. Next, to examine how humans determine grasp forces in the presence of slip on the fingertips, we conduct the experiment, in which a human touches the object which is put on a table and grasps the object using the information only from the cutaneous sensors when acceleration is applied to the object by moving the table down. Two methods that can predict when and how fingers will slip upon a grasped object are considered. Experimental results show that when slip is detected by sensing skin acceleration, the grasp force becomes much greater than the minimum force required for grasping by adding the force which is proportional to the acceleration.