Existence of feedbacks from sensing to action for stable grasping and dexterous manipulation by multi-fingered robot hands

This paper derives lumped-parameter dynamics of motion of a pair of robot fingers with soft and deformable tips pinching a rigid object. The dynamics of the system in which area contacts between the finger-tips and the surfaces of the object arise are compared with those of a pair of rigid robot fingers having rigid contacts with an object. It is then shown that even in the simplest case of dual single degree-of-freedom fingers there exists a sensory feedback from measurement of finger joint angles and the rotational angle of the object to command inputs to joint actuators and this feedback connection from sensing to action eventually realizes stable grasping of the object, provided that the object is a rectangular parallelepiped and the motion is confined to a horizontal plane. It is further shown that in the case of a pair of 1-DOF and 2-DOF fingers with soft tips there exists a sensory feedback that realizes not only stable grasping but also regulating the posture of the object at a specified rotational angle.