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Journal of Robotics
Volume 2017, Article ID 2423643, 20 pages
Research Article

Bounded Control of an Actuated Lower-Limb Exoskeleton

1F’SATI, Department of Electrical Engineering, Tshwane University of Technology, Staatsartillerie Road, Pretoria West, Pretoria, South Africa
2LISSI, University of Paris Est Creteil (UPEC), 94400 Vitry Sur Seine, France
3LISV, Bâtiment Boucher, Pole Scientifique et Technologique de Vélizy, 10-12 avenue de l’Europe, 78140 Vélizy, France

Correspondence should be addressed to Michael Oluwatosin Ajayi;

Received 20 June 2017; Accepted 24 September 2017; Published 3 December 2017

Academic Editor: Gordon R. Pennock

Copyright © 2017 Michael Oluwatosin Ajayi et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


A bounded control strategy is employed for the rehabilitation and assistance of a patient with lower-limb disorder. Complete and partial lower-limb motor function disorders are considered. This application is centered on the knee and the ankle joint level, thereby considering a user in a sitting position. A high gain observer is used in the estimation of the angular position and angular velocities which is then applied to the estimation of the joint torques. The level of human contribution is feedback of a fraction of the estimated joint torque. This is utilised in order to meet the demands for a bounded human torque; that is, The asymptotic stability of the bounded control law without human contribution and the convergence analysis of the high gain observer is verified using Lyapunov-based analysis. Simulations are performed to verify the proposed control law. Results obtained guarantee a fair trajectory tracking of the physiotherapist trajectory.