Stiffness control and calibration of robotic and human hands and fingers

In this paper, we study human grasping behavior in terms of a compliance analysis developed for modeling robot hands and fingers. The motivation is to see whether grasp compliance, which has been demonstrated to be useful for describing and controlling robotic grasps, can also capture some of the behaviors of human grasps. Force and displacement data for human grasps are used to find the stiffness matrix of the grasp by least-squares fit method. The results of this study show that the stiffness of a grasp, a linear relationship between force and displacement, is capable of capturing the experimental data of human grasps for which displacements are small (on the order of one to seven mm). Different measures, proposed and developed in the robotics literature, can be employed to predict the human grasps in reacting to externally applied loads.