Upper-limb prosthetics weight

The major factors limiting prosAeses to tools are practical ones due to the severe weight, power, and size constraints of hand/atm systems as well as the difficulty in finding a sufficient number of appropriate control sources to control the requisite number of degrees of freedom. Of these, it is the lack of independent control sources that imposes the most severe impediment to the development of today s prosthetic hand/atm systems. As a result, upper-limb prosthetics research is somewhat dominated by considerations of control. Still, the importance of better actuators and better multifunctional mechanisms must not be ignored. Control is useless if effective hand and arm mechatusms are not available. 

Although the physical design constraints of weight, volume, and power are severe, they are not so severe that multifunctional arms and hands cannot be built that would be of acceptable weight and size. The real problem is, as has been alluded to before, the issue of how to interface a multifunctional arm or hand to an amputee in a meaningful way. It is for this reason that upper-limb prosthetics is often dominated by consideration of control. That is, how can the prosthesis be controlled in such a fashion that it will be an aid rather than a burden to the user ... 

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