Abstract— Many robot hands in the literature try to achieve full kinematic anthropomorphism, and as such are often very complex and difficult/expensive to produce. This paper follows recent work that predicts that high dexterity can also be achieved through a minimal (reduced) anthropomorphic design. New experimental and simulation results that optimize grasping performance for a minimal hand are presented. A first prototype of the hand, incorporating the optimized kinematics as well as innovative endoskeletal mechanical and actuation architectures, has been designed. The robot hand prototype has been fabricated using fused deposition modelling technology, and is evaluated with respect to its grasping performance. I. INTRODUCTION The dexterous capabilities of the human hand are highly attributed to the densely packed mechanisms found inside it, resulting in a system of 21 degrees of freedom (DOFs). This has often inspired researchers to develop anthropomorphic robotic hands that replicate the functions of the human counterpart. However, this replication in the form of a robotic device has often been one of the major engineering challenges, due to the difficulty encountered in incorporating several coordinated mechanisms under stringent space and weight limitations. Such robotic devices are intended to manipulate objects that were originally designed for humans. Despite careful designing, numerous robotic hands often either lack considerable dexterous capabilities, or employ complex structures and subcomponents therefore leading to high manufacturing costs. Hence, the compromise between complexity of the design and dexterity of the artificial hand is key to an effective robotic hand design. To overcome this design challenge, several authors presented innovative approaches to enhance the dexterity of robotic hands. Okada [1] developed a highly compact robotic hand aimed for industry, having two fingers and a thumb. Tendon cables passing through the finger tubes are driven by d.c. motors. Fukaya et al. [2] constructed an artificial hand with 20 DOFs, consisting of a series of links that can be driven by a single actuator, hence facilitating the system control. Lotti et al. [3] developed a robot hand (UBH3), with cables routed inside the endoskeletal structure. As the actuators pull the cables, the skeletal elements revolve about steel spiral coils that act as the joints of the robotic hand. However, the robot hand designs presented in literature are mostly based on the respective authors’ own design approaches and intuitions. This is mainly due to the lack of availability of supportive design guidelines in this field. Although in most cases the end objectives are the same, the foundations of these robot hands differ significantly from one design to another. In a recent study [4], a novel approach was taken to provide a set of supportive design guidelines based on quantitative results. A series of constrained human manual dexterity tests were conducted to identify the contribution of each joint in the fingers. It was determined that the index finger, the middle finger and the thumb were sufficient to carry out a range of dexterous tasks. By applying this knowledge to the field of robotics, a minimal robot hand can be hypothesized. This will in theory be capable of attaining levels of dexterity comparable to that of the human hand, while employing minimum complexity. In this work, a first prototype of a minimal robotic hand based on the configuration proposed in [4] has been developed. This prototype focuses on attaining the structural, kinematic, and actuator transmission systems for the artificial hand, and does not as yet address the minimal force, sensory and control system requirements. The dexterity of the robot hand was assessed on its ability to perform a series of power and precision grasps outlined by Cutkosky in [5]. Moreover, an innovative mechanical architecture has been adopted to reduce the number of parts and complexity involved, and hence ease the manufacturing process. Due to its potential high dexterity, its inherent simplicity (with association to low cost and high robustness/reliability), and its basic anthropomorphism, an artificial hand of this nature offers significant potential for applications in humanoid robots and in prosthetics. II. DEXTERITY A. Hand Grasping The human hand is capable of grasping and manipulating objects of different geometries in various ways. These capabilities reflect the dexterity of the hand. The study and identification of the grasps that can be performed by the human hand enable the foundations for the design of the robot hand [5]. However, the identification and classification of all grasps has often been a challenging task, since grasps, in general, involve the combination of more than one finger [6]. Cutkosky [5] stated that the type of grasp performed by the hand is principally based on the task that the individual seeks to accomplish with the object. His grasping taxonomy consists of a total of sixteen principal grasps, listed in Table I. The notation in Table I will be used to refer to the different grasps throughout this text. B. Robot Hand Dexterity One of the main factors that have impeded the entry of robotic hands into human environments is their limited versatility and dexterity. This problem is often encountered Towards the Development of a Minimal Anthropomorphic Robot Hand Donald Dalli, Student Member, IEEE and Michael A. Saliba, Senior Member, IEEE D. Dalli and M. A. Saliba are with the Robotics and Industrial Automation Laboratory (RIAL) of the Department of Industrial and Manufacturing Engineering of the University of Malta, Msida, Malta MSD 2080 (phone: +356-9945-8660; fax: +356-2134-3577; e-mail: michael.saliba@um.edu.mt). 2014 14th IEEE-RAS International Conference on Humanoid Robots (Humanoids) November 18-20, 2014. Madrid, Spain 978-1-4799-7173-2/14/$31.00 ©2014 IEEE 413