Scale-Dependent Grasp.

This paper discusses the scale-dependent grasp. Suppose that an object is initially placed on a table without touching by human hand and, then he (or she) finally achieves an enveloping grasp after an appropriate approach phase. Under such initial and final conditions, human unconsciously changes the grasp strategy according to the size of object, even though they have similar geometry. We call the grasp planning the scale-dependent grasp. Focusing on column objects, we first classified the grasp patterns into a couple of grasps and extracted the essential motions so that we can apply the scale-dependent grasp to multi-fingered robot hands. We found that the grasp patterns should be also changed according to the surface friction and the geometry of cross section of object in addition to the scale. The basic strategies were verified by experiments. Finally, we considered how each strategy should be switched from one to another.