An original hybrid-architecture finger mechanism for wearable hand exoskeletons

Robotic devices for rehabilitation and assistance are becoming crucial tools for improving the life quality of people with disabilities. The hand is one of the most affected upper-limb parts, but also fundamental for the subject's interaction with the external environment. Wearability and portability, safety and comfort, lightness and small sizes, independent finger movement, efficacy in daily activities, sense-of-touch preservation, and affordability are the main features such devices should have. This paper will present an in-depth study of a thumb module for wearable hand exoskeletons, designed as a base concept to be adapted to the other fingers. Specifically, it exploits a new hybrid architecture (meaning that rigid and soft elements are included in the finger mechanism) to reduce the overall dimensions while remaining effective in force transmission. An embodiment of the mechanism is also presented and tested. As well as turning out to be small, light, and cheap, the new concept design demonstrates a minimum coverage of the finger range of motion of about 84% and an exerted force up to 16.78 N.