A Comparison of the Force Dynamics of the Precision Grip of Humans and Robots

In the field of robotics, many of studies have been published addressing the issue of grasping in robotic manipulators. A number of these discuss grasp force and present algorithms aimed at achieving the ‘optimal’ grasp force for given tasks. This paper seeks to make a comparison between these algorithms and the human grasping function. An apparatus and experimental protocol were designed to allow for the gathering of grip force data from human subjects presented with the task of keeping an object within a two-finger pinch grasp (between the thumb and index finger). This object was connected to the stylus of a PHANToM robot, which was programmed to apply various magnitudes of ‘step’ loads at random times and intervals throughout an individual trial. The object contained force sensors to measure the grip force employed by the human subject during each stage of the task. This data has been analyzed and compared to the results of the robotics algorithms for the specific task. The paper begins with background on the physiology and motor control of the hand, moves to relevant experiments in biomechanics, then touches upon some areas of cooperation between the fields of biomechanics and robotics. After this, research in robotics addressing the issue of grasping and grip force is reviewed. Finally, original research on the grip force response of human subjects to various step loads is presented and a comparison of the results to the relevant robotics algorithms is made.