A kinematic model of finger gaits by multifingered hand as hybrid automaton

Finger gait is necessarily needed in order to relocate fingers of the robotic hand when a dextrous manipulation task cannot be accomplished only by the rolling and sliding motions of the fingers. In this paper, a novel modeling framework for the multifingered manipulation with finger gaits is proposed. Through classifying the fingers into grasping fingers and free fingers, an alternate representation of a grasp is introduced. With the consideration of both its discrete and continuous characteristics, the kinematics model of a k-fingered manipulation with finger gaits is formulated into a hybrid automaton. Finally, simulation results verify the validity of the proposed modeling framework. Note to Practitioners - In some practical dextrous manipulation tasks, such as changing a bulb or using a screw driver, the robotic hand has to use a finger gait to change its grasp status sequentially in order to perform the manipulation without dissatisfying any grasping constraints. A finger gait not only causes the global discontinuity of a manipulation, but also maintains its local continuity under certain grasp status. For this reason, most currently used modeling methods are inadequate for representing manipulations with finger gaits. This paper presents a new modeling framework that formulates the kinematics model of a manipulation with finger gait as a hybrid automaton. This automaton model not only describes how a robotic hand manipulates the object, but also shows how it makes switches between different grasp modes to satisfy all manipulation requirements. Although the scope of this paper is limited to provide a well formulated model of finger gaits, in future research, our results can help to apply hybrid system techniques to answer challenging questions in robotic manipulation. For example, is a finger gait feasible to complete the manipulation task? Or how can we find an optimal gaiting strategy?.