Abstract
In this paper, we discuss the directions of active and passive force closures in hybrid active/passive-closure grasps. At first, we define the directions and derive the corresponding generalized force/displacement sets. Then, we show the directions of active and passive parts are orthogonal to each other. We also discuss the magnitudes of the internal forces in the manipulation of the object. In hybrid active/passive-closure grasps, there exist two kinds of magnitudes of internal forces. One is the magnitude which changes if the object moves and the geometry of the fingers changes. Such a magnitude has to be controlled. The other is the one which does not change even when the object moves. We only have to fix the joint torque component corresponding to such a magnitude. We derive the two kinds of magnitudes.
