Contact point identification in multi-fingered grasps exploiting kinematic constraints

Most of the algorithms used in grasp planning, force optimization and control of multifingered hands need information about the points of contact with a grasped object as well as the normal of the surface in the contact point. With no image processing, this information is gained from tactile sensor arrays, multidimensional force/torque sensors or a priori knowledge. This paper presents a method for those cases, when no good quality sensors are present or measurements are to be improved by sensor fusion. An algorithm is developed to determine the contact points and inherently the surface normal from only joint angle sensors and a geometric description of the fingertip in the 3D case. This is done by observing the constrained motion of fingers securely grasping an object.