Experimental study on human´s grasping force

We investigate the human´s characteristics of grasping behavior when disturbance forces, inertial forces or moment of rotation are acted on a grasped object. First we examine the grasping behavior when the inertial force of the object is generated. A subject grasps the experimental object with the thumb and index and ring fingers, and moves it up and down repeatedly in the vertical direction. Experimental results show that the human controls the grasping force to compensate for the inertial force acted from the object and uses the force which is just greater than the minimum force required for grasping the object. Next we investigate the grasping characteristics when the moment of rotation is acted on the object. The experimental object has a weight on one side so that its center of gravity is biased. As a result, it is found that the human controls the grasping force so as not to rotate the grasped object, the moment of inertia acted on the object can be cancelled successfully