Experimental Approach on Enveloping Grasp for Column Objects

A grasping strategy for enveloping column objects is presented. In enveloping a cylindrical object placed on a table, a multifingered robot hand can conveniently utilize the wedge effect, in which the object can be automatically lifted up through the slipping motion caused when each finger pushes the bottom part of the object[1],[2]. This paper further extends the strategy to general column objects whose cross sections are polygon. One difficult situation appears when applying the strategy for triangular or rectangular objects, because the wedge effect cannot be expected any more or becomes weak. To cope with this problem, our alternative strategy includes two additional phases before lifting the object, (1)rotating the object and (2)inserting a finger tip into the gap produced by the rotating motion. We precisely discuss how to detect the pushing point for generating the rotating motion. We also show experimental results to verify the idea proposed in the paper.