Mechanical Design of a 2-PRR Parallel Manipulator for Gait Retraining System

Abstract

Robotic gait retraining systems typically function by employing mechanisms that move a patient’s lower limbs in a controlled manner. In this paper, an end-effector gait retraining system was designed, utilizing a 2-PRR mechanism (PRR refers to the structure of each robot’s limb, consisting of an active prismatic pair (P) and two passive rotational pairs (RR) pairs). The mechanism, which corresponds to a parallel robot, was synthesized through visual design tools (design atlases) to evaluate performance indices, such as the workspace size, local and global conditioning, and mechanism stiffness. Quasi-static force analyses were conducted to calculate worst-case scenario operational loads. These loads were then used to obtain a valid cross-section geometry that would withstand static stress, buckling failure, and fatigue failure.