A Robust Control Scheme Based on Sliding Mode Observer to Drive a Knee‐Exoskeleton

• Published in: Asian journal of control Vol. 21; no. 1; pp. 439 - 455
• Main Authors: Mefoued, Saber, Belkhiat, Djamel Eddine Chouaib
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc 01.01.2019
• Subjects: Closed loops; dynamic modeling; Dynamic models; Exoskeleton device; Exoskeletons; Knee; Parameter identification; Parameter robustness; parameters identification; Proportional integral derivative; Robust control; robust controller; Sitting position; Sliding mode control; sliding mode observer; Stability analysis; Tracking errors
• DOI: 10.1002/asjc.1950
• ISSN: 1561-8625

In this paper, a robust control scheme to drive a knee‐exoskeleton has been designed to assist people with limited knee movement. Dynamic modeling and parameter identification of the “subject's lower limb‐exoskeleton” has been performed and a sliding mode observer (SMO) developed and integrated in the system's closed loop to provide velocity. Lyapunov's theory allows demonstration of the stability of the system. Experimental tests have been performed with the aid of five voluntary subjects, in sitting position, and during flexion/extension of the knee joint. The performance of the proposed control scheme is compared with those obtained using the classical proportional integrator derivative (PID) controller. These tests track the desired position and velocity trajectories with small tracking errors and evaluate the system's stability and system's robustness against the subject's parameters, variations, and external disturbances.