Path Synthesis Method for Self-alignment Knee Exoskeleton

Abstract

Axial misalignment of the exoskeleton through a purely rolling connection is unavoidable during movement, as the knee joint consists of a mixture of sliding and rolling movements. Axial misalignment can affect transmission efficiency and even create potential safety hazards. Various methods have been trying to address axial misalignment, most of which increase the complexity of the knee exoskeleton structure. In this paper, the path of the knee joint is obtained by extracting the coordinates of the knee joint motion marker points during the walking of an adult male. A power function is fitted to the path point to obtain a seventh-order polynomial function. The points on the function are taken as the target points of synthesis, and the knee path is synthesized to obtain the planar four-bar mechanism. The error between the path of the planar four-bar mechanism and the seventh polynomial function is analyzed. The results show that the planar four-bar mechanism can track the partial curve of the polynomial well. Therefore, the planar four-bar mechanism as a rotating connection can mitigate the axial misalignment.