A novel artificial hand with adaptive prehensile-behaviour

In this thesis report it will be discussed the design of a novel hand prosthesis with an innovative finger mechanism that would be able to imitate the prehensile behaviour of the human hand during the manipulation of objects. This artificial hand can act according to different strategies and trajectories during the manipulation of different types of objects, according to their size, shape and position in the environment. In any case, it is possible to distinguish two typical configurations for the manipu-lation of objects by the hand, namely a pinch action if the object is small (where the grabbing takes place by opposition of the index/middle fingers with the thumb) and a grasp action if the object has a relevant dimension if compared to the hand (where all the fingers of the hand will wrap around it, regardless of its particular shape, automatically adapting with a self-adaptive strategy) Referring to the use of soft and under-actuated mechanisms, however, it is possible to create anyway some kind of valid and effective devices, finding a simple solution for the previous critical factors. The aim of this work is therefore to propose a light and low-priced artificial mechanism that allows pinch and self-adaptive grasp in the same way, with the purpose to make the usage of the resulting artificial prosthesis as easy as possible for its final user regarding the prehensile purpose related to any type of object. For every characteristic of the target considered, the artificial hand can act in an adequate grasping strategy, despite the fact that the mechanism has a certain structure and that it is under-actuated. For releasing that the use of compliant elements instead of rigid joints was chosen with an actuation mechanism through cables, with two small electric motors to drive the whole the prosthesis, thus making the final device simple, light, cheap and effective.