Stable grasp of a 2D rigid object through rolling with soft fingers

This paper first proposes a testbed problem of control for dynamic grasp or immobilization of a 2D rigid object for the sake of gaining a physical insight into stable grasp of an object by soft fingers. Such a problem may play a principal role in understanding the methodology of sensory feedback stabilization similarly to the role of "inverted pendulum on a cart" problems in stabilization and control of mechanical systems. Second a class of coordinated control signals is proposed and shown to be effective for realizing stable grasp of a 2D rigid object in a blind manner without using the knowledge of object kinematics or external sensings. It is shown that rolling contact constraints around the centers of contact areas between soft finger-tips and object surfaces treated as nonholonomic constraints play an essential role in stabilization of a dynamic grasp with force/torque balance.