Abstract
In this paper, we propose caging grasps by prosthetic hand, which has less actuators and sensors than humans' hand. Caging is a method to make an object inescapable from a region closed by rigid bodies such as a position-controlled robot hand. We study caging methods for four kinds of object by using a dynamics simulator, and verify them with a sensorless prosthetic hand experimentally. In some cases of grasps, complete geometric enclosures by the hand are not always necessary because external forces such as gravity restrict objects' motion to escape from the incomplete enclosure by the hand. We call the situations "partial caging" where the object is partly enclosed by the hand and then the hand has some escape paths. Dynamic constraints by the external forces complement the insufficient geometric enclosure.
