Development of a Clinically Viable Multifunctional Underactuated Hand Prosthesis Using Differential Transmissions

Abstract

We are now in the process of developing a multifunctional prosthetic hand that uses six commercially available DC electric motors and transmissions in an under-actuated system to drive 16 degrees of motion. Providing greater finger dexterity as well as a wide range of major prehension patterns may require many degrees of freedom. It has been shown that increasing the number of actuators to increase the degrees of freedom can result in a complicated system with many parts which can be heavy, unreliable and costly, and therefore clinically unviable. This paper presents a design that limits the number of motors needed in the device by utilizing differentials transmissions. By limiting the number of actuators and other mechanical components, complexity is reduced and reliability is increased while still achieving a high degree of motion. The function of the differential allows for adaptive grasping through the mechanical self-adaptability of the actuators. Each digit is independently driven by one motor and transmission with the power being distributed to each of the three joints by way of a differential transmission and kinematic linkages, with an additional degree of freedom added to the thumb for palmer rotation. We believe that this will produce a highly functional prosthetic device that will be able to achieve all major prehension patterns as well as having a degree of individual finger dexterity.