Strong motivation for developing new prosthetic hand devices is provided by the fact that low functionality and controllability-in addition to poor cosmetic appearance-are the most important reasons why amputees do not regularly use their prosthetic hands. This paper presents the design of the CyberHand, a cybernetic anthropomorphic hand intended to provide amputees with functional hand replacement. Its design was bio-inspired in terms of its modular architecture, its physical appearance, kinematics, sensorization, and actuation, and its multilevel control system. Its underactuated mechanisms allow separate control of each digit as well as thumb-finger opposition and, accordingly, can generate a multitude of grasps. Its sensory system was designed to provide proprioceptive information as well as to emulate fundamental functional properties of human tactile mechanoreceptors of specific importance for grasp-and-hold tasks. The CyberHand control system presumes just a few efferent and afferent channels and was divided in two main layers: a high-level control that interprets the user's intention (grasp selection and required force level) and can provide pertinent sensory feedback and a low-level control responsible for actuating specific grasps and applying the desired total force by taking advantage of the intelligent mechanics. The grasps made available by the high-level controller include those fundamental for activities of daily living: cylindrical, spherical, tridigital (tripod), and lateral grasps. The modular and flexible design of the CyberHand makes it suitable for incremental development of sensorization, interfacing, and control strategies and, as such, it will be a useful tool not only for clinical research but also for addressing neuroscientific hypotheses regarding sensorimotor control. ObjectivesA cybernetic hand is by definition connected by a neural interface to a human and thus makes it possible to exploit sensorimotor mechanisms for controlling hand actions. While the ultimate goal of the cybernetic prosthetic hand presented in this paper (CyberHand) is to allow human amputees dexterous sensorimotor control (Fig. 1)-via a neural interface that provides efferent commands to control the hand and sensory feedback from artificial sensors-this paper focuses on the bioinspired design of this hand.Within the foreseeable future, neural interfaces will allow only a limited number of channels for exchanging efferent and afferent signals with the central nervous system (CNS) of a human. The cybernetic hand presented in this paper overcomes this limitation by its mechanical design that allows hand preshaping and specific grasping forces on the basis of only a few efferent control signals. Moreover, the integrated design makes it possible to provide task-specific feedback by utilizing a few sensory channels.

In the recent past, several researchers have shown that important variables in relearning motor skills and in changing the underlying neural architecture after stroke are the quantity, duration, content, and intensity of training sessions. Unfortunately, when traditional therapy is provided in a hospital or rehabilitation center, the patient is usually seen for few hours a week. Robot-mediated therapies could improve this situation but even if interesting results have been achieved by several groups, the use of robot-mediated therapy has not become very common in clinical practice. This is due to many different reasons (e.g., the "technophobia" of some clinicians, the need for more extensive clinical trials) but one of the more important is the cost and the complexity of these devices which make them difficult to be purchased and used in all the clinical centers.The aim of this work was to verify the possibility of improving motor recovery of hemiparetic subjects by using a simple mechatronic system. To achieve this goal, our system (named "MEchatronic system for MOtor recovery after Stroke" (MEMOS)) has been designed with the aim of using mainly "off-the-shelf products" with only few parts simply manufactured with standard technology, when commercial parts were not available. Moreover, the prototype has been developed taking into account the requirements related to the clinical applicability such as robustness and safety. * To whom correspondence should be addressed. 272Micera et al.The MEMOS system has been used during clinical trials with subjects affected by chronic hemiparesis (>6 months from the cerebrovascular accident). The results obtained during these experiments seem to show that notwithstanding the simple mechatronic structure characterizing the MEMOS system, it is able to help chronic hemiparetics to reduce their level of impairment.Further clinical experiments with acute and chronic subjects will be carried out in order to confirm these preliminary findings. Moreover, experiments for tele-rehabilitation of patients will be also carried out.

This paper presents recent results aimed at developing a functional prosthetic hand characterized by an EMG-control and by a simple and low cost fabrication technology. In order to overcome some limitations of current prosthetic hands mainly related to the poor functionality and controllability, the prosthetic hand has been designed following a biomechatronic approach based on biologically-inspired design solutions. The core of the project described in this paper is the fabrication of a compliant under-actuated prosthetic hand: the structure of the hand (both palm and fingers) is moulded as a soft polymeric single part with compliant joints and embedded tendon driven underactuated mechanism for providing adaptive grasp. In order to make user trials, the hand is equipped with simple but functional EMG-based control of the single motor incorporated in the hand, and is integrated with a prosthesis socket. The paper presents the biomechatronics design, the fabrication process, the integration of the prosthetic device and first experimental results.

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