Abstract
The ideal replacement for an amputated human limb would achieve a symbiosis with the intact human system. It should not only appear anthropomorphic; it should perform as if it were a natural extension of the human central nervous system. A prosthetic elbow for above-elbow amputees has aimed at this objective and has undergone considerable engineering refinement in parallel with simulation and evaluation studies with amputees. Efferent control is achieved by surface detection of electrical potentials generated by neuromuscular activity in the otherwise non-functional muscles in the amputees stump. Electrical intensity, related to conscious effort on the part of the amputee, controls in a proportional fashion the battery power delivered to the electric motor–gear–chain–ballscrew–linkage which rotates the elbow. Afferent reflexive feedback to the human nervous system of force-sensing information is achieved by means of a strain gauge element whose electrical output opposes the EMG signal in the limb control system. Thus a sudden increase of terminal load must be compensated for by an increase in human-generated EMG or the elbow joint will relax. Volitionally, the support or movement of greater terminal loads requires greater conscious effort. Afferent nervous system information on elbow angle will be provided by a novel vibratory display on the skin of the amputee's stump to supplement the usual visual cues. Research on this cutaneous presentation of kinaestheses indicates information transmission approaching that provided by the normal intact physiological system.
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