Preliminary Experience with Hydraulically Driven Hand Prostheses

INTRODUCTION The need for further development of prosthetic hands with enhanced functionalities and better cosmetic appearance than conventional prosthetic hands became evident in many investigations of this topic [1-3]. Consequently, a new generation of multi-articulated hands for prosthetic application were designed in the past decade. Some of these hands are characterized by a multitude of miniature DC gear motors integrated into the hand [4-8], or by an underactuated mechanism driven by a single DC motor [4,9]. However, the transition from an experimental hand to a clinically viable hand is a crucial test for any new development. Different approaches using fluidic actuators were chosen by [10] and by our research group [11]. Unlike [10], we do not use a pneumatic drive system powered by pressurized CO2 from disposable cartridges, but a compact electro-hydraulic system. Its components are micropump(s), microvalve(s), a reservoir, a controller, and small flexible fluidic actuators integrated into the finger joints. The flexible fluidic actuators expand during inflation, generating the flexion movement of the digits, whereas the extension movement is achieved by elastic elements [11]. Publications on standards for prosthetic hands and criteria to meet user requirements [1-3, 12] were analyzed and taken into consideration in designing new experimental hands. The results obtained in the first year with three hydraulically driven experimental hands are displayed and test experiences are presented.