Biomechatronic Hand

The objective of the work describe in this paper is to develop an artificial hand aimed at replicating the appearance and performance of the natural hand the ultimate goal of this research is to obtain a complete functional substitution of the natural hand. This means that the artificial hand should be felt by the user as the part of his/her own body and it should provide the user with the same functions of natural hand: tactile exploration, grasping and manipulation(“cybernetic” prosthesis). Commercially available prosthetic devices, as well as multifunctional hand designs have good reliability and robustness, but their grasping capabilities should be improved. The first significant example of an artificial hand designed according to a robotic approach is the Belgrade hand and the Utah hand which have achieved excellent results.These hands have achieved good performance in mimicking human capabilities, but there are complex devices requiring large controllers and their mass and size are not compatible with the strict requirements of prosthetic hands. 

In general, cosmetic requirements force to incorporate the entire device in a glove and to keep size and mass of the entire device comparable to that of the human hand. It turns out that the combination of robust design goals, cosmetics, and limitation of available components, can be matched only with the drastic reduction of DOF’s, as compared to those of natural hand. In fact, in prosthetic hands active bending of joints is restricted to only to two or three joints, while the other joints are fixed. Due to the lack of DOF’s prostheses are characterized by low grasping functionality and, thus they do not allow adequate encirclement of objects in comparison to the human hand; low flexibility and low adaptability of artificial fingers leads to instability of the grasp in presence of an external perturbation, as illustrated in. in conclusion commercial prostheses have been designed to be simple, robust and low cost, as the expense of their grasping ability.

This paper presents a novel multi-DOF hand several active joints, which is designed to obtain better grasping performance and natural fingers movements. The hand is designed according to a biomechatronic approach: miniature actuators and Hall- effect sensors are embedded in the hand structure in order to enable the control of available DOF’s. This paper describes a prototype of the artificial hand which has been designed, fabricated, and tested in vitro, in order to assess the feasibility of the proposed approach.