Contact point detection for grasping of an unknown object using joint compliance

Focuses on a scheme for searching a contact point between a multifingered hand and an unknown object. Instead of mounting a distributed tactile sensor all over the finger links, the authors propose an active touch approach using joint compliance. The algorithm is composed of two phases. One is the approach phase, in which each finger is opened widely and approaches to 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 with slip while maintaining contact between object and finger. Using two selected postures during the detection phase, one can compute the intersecting point which leads to an approximate contact point. 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 motion is essential in the contact point detection phase. The proposed algorithm is confirmed through simple experiments using a two-fingered robot hand