An automatic scaling procedure for a wearable and portable hand exoskeleton

The design of an aid for the hand function based on exoskeleton technologies for patients who have lost or injured hand skills, e.g. because of neuromuscular or aging diseases, is one of the most influential challenge in modern robotics to assure them an independent and healthy life. This research activity is focused on the design and development of a low-cost Hand Exoskeleton System (HES) for supporting patients affected by hand opening disabilities during the Activities of Daily Living (ADLs). In addition, the device, able to exert suitable forces on the hand, can be used during the rehabilitative sessions to implement specific tasks useful to restore the dexterity of the user's hand. The hand exoskeleton system, developed by the MDM Lab (Mechatronic and Dynamic Modelling Laboratory of the Department of Industrial Engineering, University of Florence, Italy), is based on a single-phalanx architecture and consists of a mechanical part (mechanism) and electronics (actuators, control unit and battery pack). In this paper, the authors propose a scaling procedure to automatically adapt the hand exoskeleton to different patients. Starting from the acquisition of the hand trajectories of the patients, obtained through a 3D Motion Capture (MoCap) system, a suitable optimization algorithm is used to determine the dimensions of the mechanism parts that allow to replicate at best the acquired trajectories. The optimization process showed satisfying results, permitting to obtain devices which tailor the hand of generic patients and able to reproduce the natural kinematics of the fingers.