Stiffness Compensation Mechanism for Body Powered Hand Prostheses with Cosmetic Covering

Abstract

Body powered hand prostheses require high physical user effort. This is caused by the stiffness of the cosmetic covering, or cosmetic glove. This paper aims to present a new concept of a mechanism for the compensation of the nonlinear stiffness of body powered hand prostheses by using static balancers with a nonlinear behavior. This concept is based on a cooperative action of snap-through behavior in multiple bi-stable spring mechanisms to create the nonlinear balancing force. To demonstrate the efficiency of the concept, an optimized design for a case study of a child-size hand prosthesis is also presented. A pattern search method was applied for the optimization. As a result, the calculated stiffness and thereby the operating effort was reduced by 96%. It can be concluded from the conceptual and numerical results that the presented concept provides a highly efficient solution to the discussed problem.