Contact point detection for grasping of an unknown object using self-posture changeability (SPC)

The authors focus on a scheme for searching for a contact point between a multifingered hand and an unknown object. They propose an active touch approach using joint compliance from the viewpoint of considerably reduced hardware improvement. The algorithm is composed of two phases. One is the approach phase, in which each finger first is opened widely and approaches an object until a part of a finger link is in contact with the object. The other is the detection phase, in which each finger posture is changed by slip while maintaining contact between object and finger. With a suitable combination of compliant joints and position-controlled joints, a finger link has the capability of changing its posture while maintaining contact with an object over a small angular displacement at a particular joint. This is defined as self-posture changeability (SPC). The condition leading to SPC is discussed for a general n-link system. The algorithm is confirmed through simple experiments using a two-fingered robot hand with the capability of joint compliance