Multicriteria Synthesis of a Polycentric Knee Prosthesis For Transfemoral Amputees

Abstract— In one of the prosthesis designs for lower limb transfemoral amputations artificial knee joints with polycentric mechanisms are used. Such prostheses are characterized by high stability during the stance phase of the movement. The existing variety of polycentric mechanisms indicates the possibility of finding the optimal prosthesis design satisfying several quality criteria.In this paper we present a multicriteria method for the synthesis of the artifical polycentric knee mechanism based on the uniform systematic study of the design parameters space and on the analysis of Pareto optimal solutions. Keywords— Optimalcriteria, polycentric knee, prosthesis, synthesis,transfemoral amputee.I. I NTRODUCTION OR a long period of time mankind has attempted to create artificial devices (prostheses) capable to replace as fully as possible natural human organs lost or damaged due to various reasons. First of all such devices were created to restore motor functions lost due to loss of the lower limbs. On one side, this problem seemed the most simple on a technical level, on the other side - the restoration of motor activity allows a person to carry out vital actions even with quite simple devices. The obvious drawbacks of such devices have stimulated the search for new, more sophisticated designs that could improve the quality of life for amputees. However, despite the huge technological progress made to date in this area, lower limb prostheses are still not correspond to biological analogues from different points of view [1]. Lower limb prostheses for transfemoral amputations differ by the kind of thigh and shank joint (single-axis and polycentric) and by the control methods [2].Single-axis prostheses have a fixed center of rotation of the hip relative to shank, are relatively inexpensive and with high accuracy simulate the motion of the knee. However, these prostheses have low functionality and are not sufficiently stable during the stance phase.In the polycentric prostheses position of the instant center of rotation (ICR) continuously changes with changing of the angle of knee flexion.

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