In the last few years, the number of projects studying the human hand from the robotic point of view has increased rapidly, due to the growing interest in academic and industrial applications. Nevertheless, the complexity of the human hand given its large number of degrees of freedom (DoF) within a significantly reduced space requires an exhaustive analysis, before proposing any applications. The aim of this paper is to provide a complete summary of the kinematic and dynamic characteristics of the human hand as a preliminary step towards the development of hand devices such as prosthetic/robotic hands and exoskeletons imitating the human hand shape and functionality. A collection of data and constraints relevant to hand movements is presented, and the direct and inverse kinematics are solved for all the fingers as well as the dynamics; anthropometric data and dynamics equations allow performing simulations to understand the behavior of the finger.

Stroke and other neurological pathologies are an increasing cause of hand impairment, involving expensive rehabilitative therapies. In this scenario, robotics applied to hand rehabilitation and assistance appears particularly promising in order to lower therapy costs and boost its efficacy. This work shows a recently conceived hand exoskeleton, from the design and realization to its preliminary evaluation. A control strategy based on surface electromyography (sEMG) signals is integrated: preliminary tests performed on healthy subjects show the validity of this choice. The testing protocol, applied on healthy subjects, demonstrated the robustness of the whole system, both in terms of mimicking a physiological distribution of finger forces across subjects, and of realizing an effective control strategy based on the user's intention.

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The human hand is an extremely complex system due to its large number of degrees of freedom (DoF) within a significantly reduced space. Moreover, it is required for most of the tasks performed by humans. That is why it is necessary to understand deeply all the characteristics of the human hand in order to develop devices interacting with it: to support it, to substitute injured parts, to help the recovery from injuries, or to enhance the performances while preserving its natural level of dexterity. The aim of this paper is to provide a complete and exhaustive summary of the kinematic, static and dynamic characteristics of the human hand as a preliminary step towards the development of hand devices such as prosthetic/robotic hands and exoskeletons. Both fields provide promising opportunities in research and space applications; the former through humanoid robotic helpers (e.g., Eurobot, Robonaut), the latter through the rising necessity to help the astronauts during Extravehicular Activity (EVA). In literature, several papers can be found analyzing kinematics, workspace, constraints and forces of the human hand 2,4 . However this information is scattered among several papers, regarding in particular the exerted forces and the dependencies of joint forces and velocities from the angular values of the same joint or the adjacent one. Direct and inverse kinematics are presented for all the fingers and the data related to maximum forces, velocities, acceleration for each joint of each finger has been collected and is presented in this work.