Four – bar mechanism Optimization using GA in Knee Exoskeletons

Abstract

Knee is one of the vital joints in the human body; its unique anatomical structure allows it to perform the daily life activities required as sitting, standing, walking, and etc. Subsequently, any excessive stress or injury to the knee can cause delay or inability in carrying out its daily life tasks. To regain the productivity of the knee, an exoskeleton is used whether to assist in performing the activities or in rehabilitating the injured knee. Mentioning the exoskeleton, it requires a mechanism that gives smooth and effective performance as well as have a center of rotation that changes like the knee. Taking these characteristics into consideration, the crossed four – bar mechanism is chosen and proposed in this paper to resemble the structure and the characteristics of the knee. To synthesis the suitable lengths of the mechanism, genetic algorithm (GA) optimization is carried out using MATLAB® 2022b. to validate the optimized links, an ICR analysis is carried out qualitatively and quantitively, showing a root mean square (rms) error of 9.427 mm as well as the mechanism’s output angle is compared to the desired knee angle, resulting in rms error of 5.129°. Furthermore, comparative analysis between the proposed mechanism and other cross four – bar mechanism is demonstrated. These results indicate that mechanism can be implemented to reduce the misalignment between the wearer and exoskeleton, offering smoothness and ease.