CHAD: Compact Hand-Assistive Device for enhancement of function in hand impairments

Abstract

Hand-assistive devices are used to help post-stroke victims encumbered with hand impairments perform activities of daily living (ADL). Unlike robotic rehabilitation devices used in restricted medical conditions for designated periods, hand-assistive devices are designed to be portable and to be used for extended periods by individuals engaging in ADL. Several hand-assistive device designs have been proposed. With these, designers have focused on key elements, such as size, weight, motion profile of the fingers, and generated grip/pinch force. In this paper, we propose a unique compact hand-assistive device (CHAD) that incorporates most of these design parameters, but with less trade-offs. CHAD consists of a single unit worn on the patient’s forearm, which includes all necessary components. It is compact and does not compromise functionality. The novelty of this design can be found in the use of a unique cable-driven mechanism. This mechanism uses dual linear actuators to achieve the flexion of both the index and the middle fingers via the pull of tendon-like structures originating in two selected interphalangeal joints. This permits the numerous necessary sequences in the motion profiles of the digits. The thumb is also made able to flex with a single linear actuator. Finger extensions, in contrast, are achieved passively via adjustable flexible rubber cords joined to the dorsal side of the glove. Experimental results demonstrate that CHAD generates sufficient force and motion profiles for the comfortable execution of ADL. Additionally, CHAD produces a grip and pinch motion profile similar to that of a natural hand and does not force unwanted muscle activities.