This paper presents a new design of finger proposed by the ROBIOSS team of the PPRIME Institute: it is a fully actuated bio-inspired four-degree-of-freedom (DOF) finger driven by four actuators. It has been developed with the aim to replicate fine manipulation with fingertips with a high degree of interaction with the environment. This paper proposes to realize a robotic hand for inside-hand fine manipulation and adaptive grasping. The robotic hand is equipped with fingers whose design is based on a human anatomical finger model. Thus, several fingers can be assembled for building a human-sized dexterous hand with an anthropomorphic look. The modular design offers the ability to choose the number of fingers to be used as well as to adjust finger placement based on the manipulation task requirement. The tendon-based actuation presents a routing of the tendons that minimizes friction, kinematic, and static coupling between different finger axes in the transmission from motors to joints. Unlike many existing robotic hands, including our first anthropomorphic hand, we address the difficulties by decoupling joint motions with a new solution for the universal joint at the base of the finger. The results obtained demonstrate an excellent dynamic behavior and accuracy of the finger motion. Finally, the new finger design led to the development of a fully actuated mechanical hand with four fingers and with 16 DOF: the ROBIOSS hand. The hand was embedded on an industrial robot. A manipulation task that uses simultaneously abduction-adduction motion and flexion-extension motion of the finger demonstrates the potential of the hand for accurate manipulation.

SUMMARYThis paper presents a novel tendon-driven bio-inspired robotic hand design for in-hand manipulation. Many dexterous robot hands are able to produce adaptive grasping, but only a few human-sized hands worldwide are able to produce fine motions of the object in the hand. One of the challenges for the near future is to develop human-sized robot hands with human dexterity. Most of the existing hands considered in the literature suffer from dry friction which creates unwanted backlash and non-linearities. These problems limit the accurate control of the fingers and the capabilities of the hand. Such was the case with our first fully actuated dexterous robot hand: the Laboratoire de Mécanique des Solides (LMS) hand.The mechanical design of the hand relies on a tendon-based transmission system. Developing a fully actuated dexterous robot hand requires the routing of the tendons through the finger for the actuation of each joint. This paper focuses on the evolution of the tendon routing; from the LMS hand to the new RoBioSS dexterous hand. The motion transmission in the new design creates purely linear coupling relations between joints and actuators. Experimental results using the same protocol for the previous hand and the new hand illustrate the evolution in the quality of the mechanical design. With the improvements of the mechanical behavior of the robotic fingers, the hand control software could be extensively simplified. The choice of a common architecture for all fingers makes it possible to consider the hand as a collaboration of four serial robots. Moreover, with the transparency of the motor-joint transmissions, we could use robust, industrial-grade cascaded feedback loops for the axis controls.An inside-hand manipulation task concerning the manipulation of a bottle cap is presented at the end of the paper. As proof of the robustness of the hand, demonstrations of the hand's capabilities were carried out continuously over three days at SPS IPC Drives international exhibition in Nuremberg, in November 2016.

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